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QUTE-‐EUROPE Deliverable D2.2 Second year WP2 progress report 1

QUTE-‐EUROPE (600788)

DELIVERABLE D2.2 SECOND YEAR WP2 PROGRESS REPORT


Work package number: WP2

Work package title: Coordination and Collaboration

The aim of QUTE-‐EUROPE work package 2 is to act as the main coordination link for the development of a common pan-‐European strategic vision for the field of quantum information processing, communication and technologies. As such it has been designed to engage in a variety of activities that focus on forward-‐look, anticipatory and strategy shaping actions. Specifically, in addition to maintain and update the Quantum Information Processing and Communication (QIPC) Strategic Report on a regular basis and contributing to white papers, reports and position documents, WP2 coordinates the work of QUTE-‐EUROPE Virtual Institutes; and contribute to the consolidation of Regional, National and European Research Agendas.

Task 2.1 Strategic Roadmap and other position documents

a) QIPC Strategic report

The QIPC Strategic Report (available @ http://qurope.eu/content/Roadmap) expresses the common scientific strategy, vision and goals of the European QIPC community, and has become a reference document for a wide range of stakeholders in the field. The document has been regularly updated by QUTE-‐EUROPE preceding coordination actions (ERA-‐Pilot QIST, QUROPE, and QUIE2T). Currently it is now at its 8th version; this revision, which was released in February 2013 at the end of the QUIE2T CA, was a quite important one featuring a complete rewriting of many key parts of the document. The next update will be following the major conference organized by QUTE-‐EUROPE later this fall, in which a satellite meeting of the Virtual Institutes experts will be held in order to appoint specific revision editors and organize the work.

The original DoW has been amended to reflect the delivery of the roadmap update in the Y3 of the CA.

b) Position documents

The unique position document produced this year, has been in response to an online consultation procedure launched by the Future and Emerging Technology (FET) unit, in order to identify game-‐changing directions for future research in any technological domain. The consultation targeted scientists and researchers from the widest range of disciplines, innovators, creators or interested bystanders and members of civil society in general. Its purpose was to initiate thinking about future proactive initiatives to be included in the next FET workprogramme for 2016 and 2017, similar to what was done for preparing the FET call topics for the ongoing workprogramme (2014-‐2015).

By exploiting the VI’s expertise QUTE-‐EUROPE has elaborated a joint document discussing all that can be done from the quantum technologies perspective (see attachment A).


Task 2.2 QIPC Virtual Institutes

This year has witnessed a lot of activity on the VI side.

a) Rebranding of the VI on Quantum Technologies

To begin with, a minor issue has been the renaming of the VI on Quantum Technologies, as it seems that quantum technologies is becoming the EU "wording of the Quantum Information Processing and Communication field”. Of all the possible alternatives, the name “VI on Quantum Sensing, Metrology and Imaging” was finally chosen.

b) Creation of the Virtual Facilities on Quantum Control and Quantum Engineering

During the elaboration of the position document described in Task 2.1 b) and the consequent VI’s brain storming activity for the development of a sustainability strategy for the whole area, it has become progressively clear the need to add a few new additional structures to the existing ones, which would factor in the evolution of the field from the conception of the original VIs. In fact, such new structures would:

(1) Reflect the current status of the Quantum Technologies community; (2) Raise the visibility of the identified new fields in the physics and related communities,

funding agencies and industry partners; (3) Develop a shared vision harmonized with all the existing VIs; (4) Coordinate the European efforts in the identified field.

After a quick consultation with the community in general and the QUTE-‐EUROPE Advisory Board, the areas identified were the ones of Quantum Control and Quantum Engineering. The main reasons are briefly described in the following paragraphs

Quantum Control. The CA “Optimal Control of Quantum Systems” (QUAINT, https://quantumcontrol.eu/) already started a virtual structure equivalent to a VI on Quantum Optimal Control in April 2014 as a means to promote the quantum control perspective and disseminate quantum control techniques to the broader quantum physics community. Just as in the classical world, it is control that turns scientific knowledge into useful technology, managing production lines or optimizing the flow of traffic, quantum control is essential for substantial advancement of quantum technologies towards practical applications. This builds on the established experience that quantum optimal control allows to improve relevant figures of merit by one to two orders of magnitude without requiring any other changes; examples are found in areas as diverse as optical spectroscopy, photochemistry, magnetic resonance and quantum information processing. In today's efforts to engineer quantum technologies from the bottom up, quantum optimal control has already allowed for the realization of significant milestones. For example, atomic-‐scale defects in diamonds were recently used as super-‐sensitive magnetic sensors and a better understanding of photosynthesis was used to improve the design of solar cells.

Within this framework, it was natural to include this structure among the other VIs hosted by QUTE-‐Europe as there is in fact a consensus among practitioners that the design of quantum technologies, which are based on interference and entanglement as major but rather elusive resources, will not be possible or at least be very difficult without quantum optimal control.


Its application is in particular believed to be crucial in order to reach the required precision given the sensitivity, power, timing and accuracy of instruments as well as the ever-‐present interaction with the environment that may destroy the quantum resources. Quantum control will enable goals in computation, metrology, sensing and simulation by identifying how external control knobs must be tuned to allow given hardware with all its imperfections to accomplish the required tasks in the best possible way. Quantum control is also important for quantum communication and information security, for example by improving the operation of quantum repeaters or the frequency conversion of photons as information carriers, providing a natural bridge to the VIs for Quantum Communication and Quantum Information Sciences. Finally, quantum control bundle all European activities on the control of open systems, a current challenge at the frontier of quantum physics. Quantum control is an important tool in that field as it allows for clarifying what quantum tasks can be accomplished with what precision in the presence of decoherence. It can also aid in environment engineering, i.e., in utilizing the environment to achieve what would be unattainable in a closed quantum system. This is relevant for activities under the umbrella of all QUTE-‐EUROPE VIs.

Quantum Engineering. Today many deeply interesting scientific questions remain at the level of one or two qubits. The questions which qubit representation works best for a future quantum computer or which realization of a quantum repeater is most viable, remain open as well. At the same time, within a few years, large numbers of quantum bits must be incorporated and integrated with classical electronics to realize scientific goals such as demonstrating a CNOT in a surface code (which requires of order 50 qubits combined with fast feedback for error correction). This poses important new engineering challenges in quantum computer architecture, integrated quantum-‐classical circuit design, and high-‐yield qubit fabrication. When going from 50 to 500 or 5000 qubits in say 10 years, the role of quantum engineering will grow even more important. It also raises important engineering challenges in Quantum Information theory, such as practical quantum compilers, languages and protocols for testing algorithms and simulations. In Quantum Communication typical engineering challenges involve network complexity, interfacing with other technologies, etc. and using quantum bits in metrology and sensing also requires solving engineering challenges. Some of the engineering challenges that must be overcome are either so pressing or so complex that work must be started today, despite the many important unknowns in our field. Quantum Engineering has therefore a two-‐fold objective. The first objective is to enable us to address important scientific questions in the coming years, from the demonstration of fault-‐tolerance and logical qubit operations to the realization of multi-‐node quantum networks. The second objective is to lay the foundation for real-‐world applications of quantum technologies, for which typical engineering challenges such as manufacturability, reliability and affordability all need to be addressed. The ability to perform high quality quantum engineering will turn out to be one of the main defining factors in moving forward both advancing science as in ultimately realizing innovation and economic value from quantum technologies.

Over the past few years Quantum Engineering has gained momentum. The field is still in a nascent stage, but has reached a size to be self-‐supporting. Shared visions on research challenges have emerged. Main challenges lie in device construction, devising architectures, developing (cold) electronics, multiplexing and routing of electrical and optical signals.


Several main challenges for quantum engineering are aligned with research challenges in other fields. Examples are cold electronics used in LIDAR, IR applications, pedestrian/vehicle detection in cars, and 3D integration is an important new development in classical circuit design. Early application of quantum engineering may in fact lie outside the field of quantum technology, which will help to maintain funding, but it will be the quest for quantum technology that drives the process.

The creation of these two new virtual structures has been discussed first in a teleconference on September the 16th 2014 (for the list of attendees and the agenda see Attachment B) and then in a physical meeting held at the MPQ in Garching on October the 20th 2014 (see Attachment C for the list of attendees and the agenda). Taking into consideration the fact that the proposed new virtual structures on Quantum Control and Quantum Engineering have strong interfaces with all existing VI’s, being therefore quite different in nature form the latter, it was decided to:

Keep the five existing VIs as "pillars" of the European Quantum Technologies research community, corresponding to different application goals;

Complement them with two new "horizontal" coordination structures, called Virtual Facilities (VFs) on Quantum Control and Quantum Engineering (see scheme on opposite page);

Assign a coordinating figure (Director and/or Executive Secretary) to each VF.

Each VI was then asked to indicate what their respective field needs from each of the two VFs, which were in turn asked to summarize the outcome in two additional sections to the FET consultation / white paper on sustainability. At the moment of writing this report, these new sections are in the making.

In this occasion it was also decided to enlarge the community representation in the VIs, including at the same time in the structure the geographical dimension of Europe’s main quantum research centers/clusters. Therefore it was agreed to:

Extend VI membership by up to five additional members per VI;

Get a more balanced representation over the different quantum areas across the VIs.

A procedure has been set into place in order to identify suitable representatives of the various areas. The structure that has finally emerged and approved is the summarized in the following table.


Coordinator A. Acin Virtual Institute Computation Simulation Communication Sensing Theory

Director D. Esteve I. Bloch N. Gisin I. Walmsley I. Cirac Executive Secretary

A. Wallraff S. Kuhr R. Thew K.Banaszek M. Wolf

Members

R. Blatt J. Bloch P. Grangier M. Plenio H. Buhrman D. DiVincenzo J. Eisert R. Renner E. Polzik M. Troyer D. Loss M. Inguscio G. Ribordy J. Wrachtrup S. Wehner P. Zoller M. Lewenstein A. Shields R. Werner L. Vandersypen R. Ursin A. Winter

Virtual Facility Engineering Control

C. Marcus S. Glaser J. Morton F. Wilhelm This has resulted in an enlarged Strategic Advisory Board which is now composed by the following scientists:

1. Antonio Acin 2. Konrad Banaszek 3. Rainer Blatt 4. Immanuel Bloch 5. Harry Buhrman 6. Vladimir Buzek 7. Tommaso Calarco (chair) 8. Nicolas Cerf 9. Ignacio Cirac 10. Artur Ekert 11. Daniel Esteve 12. Elisabeth Giacobino 13. Steffen Glaser 14. Stefan Kuhr 15. Nicolas Gisin 16. Atac Imamoglu 17. Massimo Inguscio 18. Peter Knight 19. Leo Kouwenhoven 20. Stefan Kuhr 21. Maciej Lewenstein 22. Charles Marcus 23. John Morton 24. Martin Plenio 25. Eugene Polzik 26. Gerhard Rempe 27. Rob Thew 28. Andreas Wallraff, 29. Ian Walmsley 30. Reinhard Werner


31. Frank Wilhelm-‐Mauch 32. Michael Wolf 33. Anton Zeilinger 34. Peter Zoller

Notice that the carried out restructuring of the Virtual Institutes together with the addition of the

Virtual Facilities should be considered the final part for the fulfillment of MS3 “Creation of a communication scheme for providing VIs expertise”.

c) Virtual Institutes highlights As usual, the different Virtual Institutes (VI) within QUTE-‐EUROPE prepared a selection of the scientific highlights of the year 2013. The present report presents these highlights, structured according to the VI’s.

Quantum Computation VI highlights

This VI for Quantum Computation integrates all groups which have an effort aiming at building a large scale quantum computer, independently of the physical system used for this purpose (since as the QIPC Strategic report clearly states in its Executive Summary “[...] it is too early to pick the winner implementation for the practical realization of a working quantum device”). These includes trapped ions and neutral atoms, cavity QED, solid state devices (such as superconducting qubits, possibly in combination with circuit cavity QED, and spin qubits), all-‐optical devices, as well as impurity spins in solids, single molecular magnets, and all sort of hybridization between these different implementations.

The highlights of the year 2014 for this VI are the following:

Electrical control of a long-‐lived spin qubit in a Si/SiGe quantum dot E. Kawakami, P. Scarlino, D. R. Ward, F. R. Braakman, D. E. Savage, M. G. Lagally, M. Friesen, S. N. Coppersmith, M. A. Eriksson, L. M. K. Vandersypen Nature Nanotechnology 9, 666-‐670 (2014);

An addressable quantum dot qubit with fault-‐tolerant control-‐fidelity M. Veldorst, J. C. C. Hwang, C. H. Yang, A. W. Leenstra, B. de Ronde, J. P. Dehollain, J. T. Muhonen, F. E. Hudson, K. M. Itoh, A. Morello, A.S. Dzurak Nature Nanotechnology 9, 981–985 (2014);

Storing quantum information for 30 seconds in a nanoelectronic device J. T. Muhonen, J. P. Dehollain, A. Laucht, F. E. Hudson, T. Sekiguchi, K. M. Itoh, D. N. Jamieson, J. C. McCallum, A. S. Dzurak, A. Morello Nature Nanotechnology 9, 986–991 (2014)

Electron spins in semiconductors are promising candidates for quantum computation because they can be built on microelectronics technology and exhibit a weak interaction with the solid-‐state host material. Using silicon as a host material for these qubits represents a promising solution since dephasing and decoherence times are expected to be long due to the (near) absence of nuclear spins. However, most pioneering works so far are difficult to scale up, or use materials in which the


interaction between electron and nuclear spins is still strong enough to heavily disturb the phase of the electron spins, thus destroying the information stored in the qubit very quickly.

These three works, appearing in the same issue of Nature Technology, confirm the expectations and demonstrate that individual electron spins in silicon are indeed highly decoupled from their environment and can be controlled coherently with high accuracy. All the three works define a single electron spin as one qubit, but each one follows its own approach to confine this single electron in some nanoscale device. The three projects report good coherence times, especially the third one, and fidelities close to the required value for quantum error correction. These results show that electron spins in silicon represent a promising candidate for fault tolerant qubits.

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Quantum control and process tomography of a semiconductor quantum dot hybrid qubit D. Kim, Z. Shi, C. B. Simmons, D. R. Ward, J. R. Prance, T. S. Koh, J. K. Gamble, D. E. Savage, M. G. Lagally, M. Friesen, S. N. Coppersmith, M. A. Eriksson Nature 511, 70-‐74 (2014)

Encoding quantum information in semiconductor quantum dots offers long coherence times. However, their manipulation is often slower than desired. Previous work has increased the speed of spin qubit rotations by making use of integrated micromagnets, dynamic pumping of nuclear spins or the addition of a third quantum dot. However, these alternatives increase the complexity of the setup, which, in turn, make scalability and manufacturability more challenging.

In their work, Kim and co-‐workers demonstrate a quantum-‐dot qubit that is a hybrid of spin and charge. It is simple, requiring neither nuclear-‐state preparation nor micromagnets. The hybrid qubit contains three electrons in two dots and has the advantage of allowing all-‐electrical qubit manipulation without the need for microwave driving or local magnetic field gradients. The name “hybrid” derives from the fact that the qubit has both spin and charge character. The charge aspect allows also for very fast manipulation, though at the same time it limits the qubit coherence compared to its relatives. The researchers demonstrate that hybrid qubits allow for fast rotations along two axes of the Bloch sphere with fidelities of 85% in the X direction and 95% in the Z direction.

Superconducting quantum circuits at the surface code threshold for fault tolerance R. Barends, J. Kelly, A. Megrant, A. Veitia, D. Sank, E. Jeffrey, T. C. White, J. Mutus, A. G. Fowler, B. Campbell, Y. Chen, Z. Chen, B. Chiaro, A. Dunsworth, C. Neill, P. O’Malley, P. Roushan, A. Vainsencher, J. Wenner, A. N. Korotkov, A. N. Cleland, J. M. Martinis Nature 508, 500-‐503 (2014);

Quantum computations on a topologically encoded qubit D. Nigg, M. Müller, E. A. Martinez, P. Schindler, M. Hennrich, T. Monz, M. A. Martin-‐Delgado, R. Blatt Science 345, 302-‐305 (2014)

Quantum error correction is an essential ingredient for quantum computation implementations: quantum information can be protected by distributing a logical quantum state among many physical qubits by means of quantum entanglement. Both of these works report the implementation of


quantum error correcting techniques in two different technological platforms: superconducting circuits and trapped ions.

In the case of superconducting qubits, the surface code is a natural choice for error correction, since it uses only nearest-‐neighbour coupling and rapidly cycled entangling gates. Moreover, the gate fidelity requirements are modest, with fidelity thresholds of about 99%. In their work, Barends and co-‐workers demonstrate a universal set of logic gates in a superconducting multi-‐qubit processor, achieving an average single-‐qubit gate fidelity of 99.92% and a two-‐qubit gate fidelity of up to 99.4%. This reported setup represents a first step towards the surface code, using five qubits arranged in a linear array with nearest-‐neighbour coupling. The results demonstrate that viability of Josephson quantum computing as a path to scalable fault-‐tolerant quantum circuits.

In the case of trapped ions, Nigg and co-‐workers report a quantum error-‐correcting code in which one qubit is encoded in entangled states distributed over seven trapped ions. The code can detect one bit flip error, one phase flip error, or a combined error of both, regardless on which of the qubits they occur. Sequences of gate operations are applied on the encoded qubit to explore its computational capabilities. This seven-‐qubit code represents a fully functional instance of a topologically encoded qubit, or color code, and opens a route toward fault-‐tolerant quantum computing.

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Coherent suppression of electromagnetic dissipation due to superconducting quasiparticles I. M. Pop, K. Geerlings, G. Catelani, R. J. Schoelkopf, L.I. Glazman, M. H. Devoret Nature 508, 369–372 (2014)

While superconducting qubits represent a promising technological platform for quantum computation, a good enough control of the mechanisms of decoherence and dissipation in these systems is still an experimental challenge. In particular, Josephson’s key theoretical prediction that quasiparticle dissipation should vanish in transport through a junction when the phase difference across the junction is π has never been observed.

In their work, Pop and co-‐workers report the experimental observation of this quantum coherent suppression of the quasiparticle dissipation across a Josephson junction. The suppression of dissipation, despite the presence of lossy quasiparticle excitations above the superconducting gap, provides a powerful tool for minimizing decoherence in quantum electronic systems and could be directly exploited in quantum information experiments with superconducting quantum bits. In particular, coherence times, which have always been determined by extrinsic factors, are now limited by physics intrinsic to Josephson tunneling, achieving relaxation times well above 1 ms in artificial atoms (an increase by two orders of magnitude from previous works). Quantum Communication VI highlights This institute incorporates all groups, both theory and experimental, working in the field. Quantum Communication can be defined as the art of transferring quantum states from one place to another. The general idea is that quantum states encode quantum information: hence quantum communication also implies transmission of quantum information. Quantum Communication covers diverse aspects of basic physics, such as quantum optics, solid state physics and more, as well as addressing more practical issues related to implementing quantum key distribution protocols and


quantum cryptography. Additionally, it takes care of the whole “wiring” inside a quantum computer or simulator, contributing to quantum repeaters, interfaces and various hybrid technologies for developing complex quantum networks. The highlights of the year 2014 for this VI are the following:

Quantum teleportation from a telecom-‐wavelength photon to a solid-‐state quantum memory F. Bussières, C. Clausen, A. Tiranov, B. Korzh, V. B Verma, S.W. Nam, F. Marsili, A. Ferrier, P. Goldner, H. Herrmann, C. Silberhorn, W. Sohler, M. Afzelius, N. Gisin Nature Photonics 8, 775-‐778 (2014);

Unconditional quantum teleportation between distant solid-‐state quantum bits W. Pfaff, B.J. Hensen, H. Bernien, S.B. van Dam, M.S. Blok, T.H. Taminiau, M.J. Tiggelman, R.N. Schouten, M. Markham, D.J. Twitchen, R. Hanson Science 345, 532-‐535 (2014)

Quantum teleportation allows for the transfer of arbitrary, in principle, unknown quantum states from a sender to a spatially distant receiver, who share an entangled state and can communicate classically. It is essential for long-‐distance transmission of quantum information using quantum repeaters. This requires the efficient distribution of entanglement between remote nodes of a network. These two works report two significant experimental demonstrations of quantum teleportation, in solid-‐state quantum memories and between defects in diamond.

In the first work, Bussières and co-‐workers demonstrate quantum teleportation of the polarization state of a telecom-‐wavelength photon onto the state of a solid-‐state quantum memory. Entanglement is established between a rare-‐earth-‐ion-‐doped crystal storing a single photon that is polarization-‐entangled with a flying telecom-‐wavelength photon. The latter is jointly measured with another flying polarization qubit to be teleported, which heralds the teleportation. The fidelity of the qubit retrieved from the memory is shown to be greater than the maximum fidelity achievable without entanglement, even when the combined distances travelled by the two flying qubits is 25 km of standard optical fibre. These results demonstrate the possibility of long-‐distance quantum networks with solid-‐state resources.

In the second work, Pfaff and co-‐workers demonstrate unconditional teleportation of arbitrary quantum states between diamond spin qubits separated by 3 meters. The teleporter is prepared through photon-‐mediated heralded entanglement between two distant electron spins. The source qubit is encoded in a single nuclear spin. By realizing a fully deterministic Bell-‐state measurement combined with real-‐time feed-‐forward, quantum teleportation is achieved upon each attempt with an average state fidelity exceeding the classical limit. These results establish diamond spin qubits as a prime candidate for the realization of quantum networks for quantum communication and network-‐based quantum computing.

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A quantum gate between a flying optical photon and a single trapped atom Reiserer, N. Kalb, G. Rempe, S. Ritter Nature 508, 237-‐240 (2014);

Nanophotonic quantum phase switch with a single atom T. G. Tiecke, J. D. Thompson, N. P. de Leon, L. R. Liu, V. Vuletic, M. D. Lukin


Nature 508, 241-‐244 (2014);

Nonlinear π phase shift for single fibre-‐guided photons interacting with a single resonator-‐enhanced atom J. Volz, M. Scheucher, C. Junge, A. Rauschenbeutel Nature Photonics 8, 965-‐970 (2014);

Nonlinear Interaction between Single Photons T. Guerreiro, A. Martin, B. Sanguinetti, J. S. Pelc, C. Langrock, M. M. Fejer, N. Gisin, H. Zbinden, N. Sangouard, R.T. Thew Phys. Rev. Lett. 113, 173601 (2014)

Nonlinear optics made significant progress in 2014 with several experimental results demonstrating optical gates, or switches, based on atomic systems that respond at the single photon level, or photon-‐photon interactions.

In the first work, Reiserer and co-‐workers implement a quantum gate between the spin state of a single trapped atom and the polarization state of an optical photon contained in a faint laser pulse. The gate mechanism is deterministic and robust, and is expected to be applicable to almost any matter qubit. It is based on reflection of the photonic qubit from a cavity that provides strong light–matter coupling. To demonstrate its versatility, they use the quantum gate to create atom–photon, atom–photon–photon and photon–photon entangled states from separable input states.

In the second work, Tiecke and co-‐workers, by strongly coupling a photon to a single atom trapped in the near field of a nanoscale photonic crystal cavity, realize a system in which a single atom switches the phase of a photon and a single photon modifies the atom’s phase. They experimentally demonstrate an atom-‐induced optical phase shift that is nonlinear at the two-‐photon level, a photon number router that separates individual photons and photon pairs into different output modes, and a single-‐photon switch in which a single ‘gate’ photon controls the propagation of a subsequent probe field.

In the third work, Volz and co-‐workers, implement a strong interaction between individual photons. They demonstrate a fibre-‐based nonlinearity that realizes an additional two-‐photon phase shift close to the ideal value of π. They employ a whispering-‐gallery-‐mode resonator, interfaced by an optical nanofibre, where the presence of a single rubidium atom in the resonator mode results in a strongly nonlinear response. They show that this results in entanglement of initially uncorrelated incident photons, which represents an important step towards photon-‐based scalable quantum logics.

In the last work, Guerreiro and co-‐workers report the nonlinear interaction between two single photons. Each photon is first generated in independent parametric down-‐conversion sources. They are subsequently combined in a nonlinear waveguide where they are converted into a single photon of higher energy by the process of sum-‐frequency generation. This results in the direct generation of photon triplets. This work highlights the potential for quantum nonlinear optics with integrated devices, with applications in quantum communication such as device-‐independent quantum key distribution.

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Bidirectional and efficient conversion between microwave and optical light R. W. Andrews, R. W. Peterson, T. P. Purdy, K. Cicak, R. W. Simmonds, C. A. Regal, and K. W. Lehnert Nature Physics 10, 321-‐326 (2014)

Hybrid quantum systems that allow for the transduction between different operating regimes and different physical systems are key enabling technologies for complex quantum systems. A microwave-‐to-‐optical converter in a quantum information network could be useful to link quantum processors through low-‐loss optical fibres and enabling a large-‐scale quantum network. However, no current technology can convert low-‐frequency microwave signals into high-‐frequency optical signals while preserving their quantum state.

In their work, Andrews and co-‐workers demonstrate a converter that provides a bidirectional, coherent and efficient link between the microwave and optical portions of the electromagnetic spectrum. The converter is used to transfer classical signals between microwave and optical light with conversion efficiencies of ∼10%, and achieve performance sufficient to transfer quantum states if the device were further precooled from its current 4 K operating temperature to temperatures below 40 mK. The implementation attains a conversion efficiency of four orders of magnitude over previous efforts.

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Measurement-‐Device-‐Independent Quantum Key Distribution over 200 km Y-‐L. Tang, H-‐L. Yin, S-‐J.Chen, Y. Liu, W-‐J. Zhang, X. Jiang, L. Zhang, J. Wang, L-‐X. You, J-‐Y. Guan, D-‐X. Yang, Z. Wang, H. Liang, Z. Zhang, N. Zhou, X. Ma, T-‐Y. Chen, Q. Zhang, and J-‐W. Pan Phys. Rev. Lett. 113, 190501 (2014)

Measurement-‐device–independent quantum key distribution (MDIQKD) represents a valid alternative for quantum cryptography. It requires fewer assumptions for security than standard prepare-‐and-‐measure schemes, while its implementation is less demanding than fully device-‐independent protocols.

In their work, Tang and co-‐workers report the first long-‐distance implementation of MDIQKD. By developing a 75 MHz clock rate fully automatic and highly stable system and superconducting nanowire single-‐photon detectors with detection efficiencies of more than 40%, they demonstrate the secure implementation of MDIQKD up to distances of the order of 200 km and achieve a secure key rate 3 orders of magnitude higher than previous efforts. These results provide the most advanced demonstration of this technique.

Quantum Information Sciences VI highlights This Institute comprises all theoretical efforts in the field. In fact, the development of QIPC has been driven by theoretical work of scientists working on the boundary between Physics, Computer Science, Mathematics, and Information Theory. In the early stages of this development, theoretical work has often been far ahead of experimental realization of these ideas. At the same time, theory has provided a number of proposals of how to implement basic ideas and concepts from quantum information in specific physical systems. These ideas are now forming the basis for successful experimental work in the laboratory, driving forward the development of tools that will in turn form


the basis for all future technologies which employ, control and manipulate matter and radiation at the quantum level.


Ultimate classical communication rates of quantum optical channels V. Giovannetti, R. Garcia-‐Patrón, N. J. Cerf, A. S. Holevo Nature Photonics 8, 796-‐800 (2014)

Optical channels, such as fibers or free-‐space links, are ubiquitous in today's telecommunication networks. A complete physical model of these channels must necessarily take quantum effects into account to determine their ultimate performances. Single-‐mode, phase-‐insensitive bosonic Gaussian channels have been extensively studied over past decades, given their importance for practical applications. In spite of this, a long-‐standing unsolved conjecture on the optimality of Gaussian encodings has prevented finding their classical communication capacity.

In their work, Giovannetti and co-‐workers solve this conjecture by proving that the vacuum state achieves the minimum output entropy of these channels. This establishes the ultimate achievable bit rate under an energy constraint, as well as the long awaited proof that the single-‐letter classical capacity of these channels is additive. This result represents a breakthrough in quantum information theory, solving a long-‐standing open conjecture.

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Disproving the Peres conjecture by showing Bell nonlocality from bound entanglement T. Vértesi, N. Brunner Nature Communications 5, 5297 (2014)

Quantum entanglement and quantum nonlocality are among the most central phenomena in the field of quantum information theory, being responsible for the advantage of quantum protocols over classical ones for information processing. Although related, the exact connection between these two concepts is still not completely understood. In 1999, Peres conjectured that nonlocal correlations could only be observed on quantum states with distillable entanglement. Since there exist undistillable states, called bound entangled states, if Peres conjecture was true it would mean that this class of states would be useless for any quantum information protocols that require nonlocality.

In their work, Vertesi and Brunner disprove the Peres conjecture by showing that bipartite bound entangled state can violate a Bell inequality, that is, it shows nonlocal correlations although it is not possible to distill its entanglement. This work also solves a long-‐standing conjecture in the field.

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Local tests of global entanglement and a counterexample to the generalized area law D. Aharonov, A. W. Harrow, Z. Landau, D. Nagaj, M. Szegedy, U. Vazirani Proceedings of FOCS 2014, 246 (2014)

Maximally entangled states are a valuable resource for quantum information tasks and detecting its presence represents a very meaningful question. Can two parties test whether their joint state is maximally entangled while exchanging only a constant number of qubits? A seemingly unrelated


question is the validity of the generalized area law for the growth of entanglement on ground states of quantum many body systems. Specifically, it considers lattice systems described by gapped local Hamiltonians, i.e. where only local interactions between two neighboring particles are allowed. The area law conjectures that for every bipartition of the system, the amount entanglement in the ground state is bounded by a constant times the size of the boundary of the system.

In their work, Aharonov and co-‐workers develop a new technique using quantum expanders that provides a definite answer for both questions. They show that, surprisingly, a constant amount of resources is sufficient to verify a global property of a bipartite quantum system, namely the state being maximally entangled. On the other hand, they disprove the generalized area law conjecture by providing a counterexample.

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Exponential improvement in precision for simulating sparse Hamiltonians D. W. Berry, A. M. Childs, R. Cleve, R. Kothari, R. D. Somma Proceedings of the 46th ACM Symposium on Theory of Computing (STOC 2014), 283-‐292 (2014)

Simulation of quantum mechanical systems is a major potential application of quantum computers.

Indeed, the problem of simulating Hamiltonian dynamics was the original motivation for the idea of quantum computation.

In their work, Berry and co-‐workers provide a quantum algorithm for simulating the dynamics of sparse Hamiltonians with complexity sublogarithmic in the inverse error, an exponential improvement over previous methods. Unlike previous approaches based on product formulas, the query complexity is independent of the number of qubits acted on, and for time-‐varying Hamiltonians, the gate complexity is logarithmic in the norm of the derivative of the Hamiltonian. The algorithm is based on a significantly improved simulation of the continuous, and fractional, query models using discrete quantum queries, showing that the former models are not much more powerful than the discrete model even for very small error. Finally, they prove that the algorithm is optimal as a function of the error.

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Fully device independent quantum key distribution U. Vazirani, T. Vidick Phys. Rev. Lett. 113, 140501 (2014)

Although quantum key distribution (QKD) is one of the major achievements of quantum information science, its security proofs rely on certain assumptions on the devices used in the protocol. To overcome this serious limitation, device-‐independent QKD (DIQKD) has been developed as a method to guarantee security even in the case the devices are uncharacterized. Much effort has been devoted in devising DIQKD protocols that extract an amount of key that is linear in the number of uses of the devices, which are secure against increasingly general eavesdropping strategies and are robust to the presence of noise. However, the best known protocols were either based on the assumption that the devices had no internal memory or were polynomially inefficient and unable to


tolerate noisy devices. This raised an essential question: is device-‐independent QKD even possible without independence assumptions in a realistic, noise-‐tolerant scenario?

In their work, Vazirani and Vidick give a positive answer to this important question. They provide the first complete device-‐independent proof of security of quantum key distribution that tolerates a constant noise rate and guarantees the generation of a linear amount of key.

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Detecting nonlocality in many-‐body quantum states J. Tura, R. Augusiak, A. B. Sainz, T. Vértesi, M. Lewenstein, and A. Acín Science 344, 1256 (2014)

Numerous studies have been carried out regarding entanglement of many-‐body quantum systems particles, since it proves to be a fundamental key aspect to understanding their properties. However, very little work has been done concerning the nonlocality of these systems, simply because the known Bell inequalities involve correlations among many parties which are out of reach within the current experimental technology. As a consequence, nonlocality of many-‐body quantum systems cannot be tested experimentally

In their work, Tura and co-‐workers designed classes of multipartite Bell inequalities constructed from the easiest-‐to-‐measure quantities, the two-‐body correlators. These inequalities are, nevertheless, capable of revealing the nonlocality properties of many-‐body quantum states, in particular those relevant for nuclear and atomic physics. In addition, the inequalities proposed by this study, can be verified by measuring the total spin components of the particles, which opens a new window to experimental detection of many-‐body nonlocality in physical systems in which individual particles cannot be addressed. Quantum Metrology, Sensing and Imaging VI highlights

Many branches of QIPC have gone past the proof-‐ of-‐principle phase, and in the short term the first technological applications of quantum coherence and entanglement will appear. This institute embraces all groups/industries working on the different aspects of these technologies which can be split into two main categories: either technologies that represent genuine applications of QIPC (e.g., quantum cryptography, quantum metrology, quantum imaging, quantum random number generators, etc.), or technologies instrumental in developing QIPC devices (e.g., single-‐ and entangled-‐photon sources and detectors, chips for ion and atom traps, etc.).


Using Entanglement Against Noise in Quantum Metrology R. Demkowicz-‐Dobrzański, L. Maccone Phys. Rev. Lett. 113, 250801 (2014)

Quantum metrology provides super-‐classical scaling in measurement precision by exploiting quantum effects. A crucial question in the field is to understand when entangled states lead to super-‐classical scaling.


In their work, Demkowicz-‐Dobrzański and Maccone analyze the role of entanglement among probes and with external ancillas in quantum metrology. In the absence of noise, it is known that unentangled sequential strategies can achieve the same Heisenberg scaling of entangled strategies and that external ancillas are useless. This changes in the presence of noise; the work proves that entangled strategies can have higher precision than unentangled ones and that the addition of passive external ancillas can also increase the precision. They also analyze some specific noise models and use the results to conjecture a general hierarchy for quantum metrology strategies in the presence of noise.

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Joint estimation of phase and phase diffusion for quantum metrology M. D. Vidrighin, G. Donati, M. G. Genoni, X.-‐M. Jin, W. S. Kolthammer, M. S. Kim, A. Datta, M. Barbieri,, I. A. Walmsley Nature Communications 5, 3532 (2014)

Phase estimation is one of the most studied quantum metrology situations, with wide-‐ranging practical applications. In many realistic situations, phase and phase diffusion may vary in time. Consequently, the accuracy of phase estimation may be affected by varying estimates of the magnitude of phase diffusion.

In their work, Vidrighin and co-‐workers investigate the joint estimation of a phase shift and the amplitude of phase diffusion at the quantum limit. For several relevant instances, this multiparameter estimation problem can be effectively reshaped as a two-‐dimensional Hilbert space model, encompassing the description of an interferometer phase probed with relevant quantum states. For these cases, a trade-‐off bound is derived on the statistical variances for the joint estimation of phase and phase diffusion, as well as optimum measurement schemes. This bound is then used to quantify the effectiveness of an actual experimental set-‐up for joint parameter estimation for polarimetry.

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Heisenberg-‐Limited Atom Clocks Based on Entangled Qubits E. M. Kessler, P. Kómár, M. Bishof, L. Jiang, A. S. Sørensen, J. Ye, M. D. Lukin Phys. Rev. Lett. 112, 190403 (2014)

The improvement of frequency standards using quantum resources, such as entanglement has been actively explored in recent years. The use of entangled resources, in principle, allows one to surpass the classical limit on precision. However, a characterization of the improvement obtainable by using entanglement requires a detailed investigation of the decoherence present in the system.

In their work, Kessler and co-‐workers present a quantum-‐enhanced atomic clock protocol based on sets of sequentially larger Greenberger-‐Horne-‐Zeilinger (GHZ) states that achieve the best clock stability allowed by quantum theory up to a logarithmic correction. Importantly, the protocol is designed to work under realistic conditions where the drift of the phase of the laser interrogating the atoms is the main source of decoherence. They compare and merge the new protocol with existing state of the art interrogation schemes, and identify the precise conditions under which entanglement


provides an advantage for clock stabilization: it allows a significant gain in the stability for short averaging time.

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Increasing Sensing Resolution with Error Correction G. Arrad, Y. Vinkler, D. Aharonov, A. Retzker Phys. Rev. Lett. 112, 150801 (2014);

Quantum Error Correction for Metrology E. M. Kessler, I. Lovchinsky, A. O. Sushkov, M. D. Lukin Phys. Rev. Lett. 112, 150802 (2014);

Improved Quantum Metrology Using Quantum Error Correction W. Dür, M. Skotiniotis, F. Fröwis, B. Kraus Phys. Rev. Lett. 112, 080801 (2014)

Understanding quantum metrology in noisy environments is crucial for the development of quantum sensing techniques. In particular, it is relevant to know where the effect of noise and decoherence limits the achievable gain in precision by quantum entanglement.

These works consider the use of quantum error correction techniques to improve the sensitivity of quantum metrology in noisy scenarios.

In the first work, Arrad and co-‐workers utilize quantum error correction to prolonging the coherence time of sensing protocols beyond the fundamental limits of current techniques. They develop an implementable sensing protocol that incorporates error correction, and discuss the characteristics of these protocols in different noise and measurement scenarios. They examine the use of entangled versus separable states, and error correction’s reach of the Heisenberg limit. They show that measurement precision can be enhanced for both one-‐directional and general noise.

In the second work, Kessler and co-‐workers also analyze the use of quantum error correction to improve quantum metrology in the presence of noise. They identify the conditions under which these techniques allow one to improve the signal-‐to-‐noise ratio in quantum-‐limited measurements, and demonstrate that it enables, in certain situations, Heisenberg-‐limited sensitivity. They finally discuss specific applications to nanoscale sensing using nitrogen-‐vacancy centers in diamond and show improvements on the measurement sensitivity and bandwidth under realistic experimental conditions.

In the third work, Dür and co-‐workers also show how quantum error correction techniques improve the achievable gain in precision by quantum entanglement in some noisy situations. This is demonstrated in two scenarios, including a many-‐body Hamiltonian with single-‐qubit dephasing or depolarizing noise and a single-‐body Hamiltonian with transversal noise. In both cases, Heisenberg scaling, and hence a quadratic improvement over the classical case, can be retained. For the case of frequency estimation they find that the inclusion of error correction allows, in certain instances, for a finite optimal interrogation time even in the asymptotic limit.

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Quantum seismology E. G. Brow, W. Donnelly, A. Kempf, R. B. Mann, E. Martín-‐Martínez, and N. C. Menicucci New Journal of Physics 16, 105020 (2014)

Entanglement farming is a protocol that involves successively sending pairs of “particle detectors” (such as atoms, ions, molecules, etc) transversely through an optical cavity. As pair after pair traverses the cavity, the field approaches a fixed-‐point state, where every pair of atoms emerges from the cavity in the same state, which is generically entangled. The fixed point is generally stable to small changes in the parameters.

In their work, Brow and co-‐workers show that this robustness breaks down dramatically when the frequency at which atoms traverse the cavity is at resonance with a multiple of the cavity’s fundamental frequency.

They use this effect to propose a quantum mechanical method of detecting weak vibrational disturbances. Taking advantage of an extremely precise resonance effect, it is possible to find a regime where the fixed-‐point state is highly sensitive to perturbations, even harmonic vibrations with frequencies several orders of magnitude below the cavityʼs natural frequency. This sensitivity may be useful for high precision metrology.

Quantum Simulation VI highlights

Quantum simulation (QS) of physical and artificial systems is now becoming the focus of many branches of QIPC. Some branches are already mature enough to perform groundbreaking QS experiments and implementations, while for other branches QS constitutes a driver of the development of powerful hardware platforms and protocols. This institute provides a common agenda and a common language for all QIPC groups and projects. It is cross-‐disciplinary and directly addresses the kind of development that is expected to be the main QIPC road in at least the short term. It embraces transformational aspects in a unified manner, preparing useful applications to profit from progress in hardware, and providing a driver for quantum technologies and the scaling up QIPC platforms.


Experimental realization of the topological Haldane model with ultracold fermions G. Jotzu, M. Messer, R. Desbuquois, M. Lebrat, T. Uehlinger, D. Greif, T. Esslinger Nature 515, 237–240 (2014);

Observation of topological transitions in interacting quantum circuits P. Roushan, C. Neill, Y. Chen, M. Kolodrubetz, C. Quintana, N. Leung, M. Fang, R. Barends, B. Campbell, Z. Chen, B. Chiaro, A. Dunsworth, E. Jeffrey, J. Kelly, A. Megrant, J. Mutus, P. J. J. O’Malley, D. Sank, A. Vainsencher, J. Wenner, T. White, A. Polkovnikov, A. N. Cleland, J. M. Martinis Nature 515, 241–244 (2014)

The discovery of topological phases in condensed-‐matter systems has changed the modern conception of phases of matter. The Haldane model on a honeycomb lattice is a paradigmatic example of a Hamiltonian featuring topologically distinct phases of matter. In fact, the model has


provided the conceptual basis for theoretical and experimental research exploring topological insulators and superconductors.

These two works report the experimental simulation of the Haldane model in two different platforms, namely optical lattices and superconducting circuits.

In the case of optical lattices, Jotzu and co-‐workers report the experimental realization of the Haldane model and the characterization of its topological band structure, using ultracold fermionic atoms in a periodically modulated optical honeycomb lattice. In the setup, time-‐reversal symmetry and inversion symmetry are broken, which opens a gap in the band structure. The competition between the two broken symmetries gives rise to a transition between topologically distinct regimes. The approach, which allows for tuning the topological properties dynamically, is suitable even for interacting fermionic systems. This work represents a crucial step towards cold-‐atom realizations of exotic phenomena such as fractional quantum Hall phases and fractional Chern insulators.

In the case of superconducting circuits, Roushan and co-‐workers investigate basic topological concepts of the Haldane model after mapping the momentum space of this condensed-‐matter model to the parameter space of a single-‐qubit Hamiltonian. In addition to constructing the topological phase diagram, they visualize the microscopic spin texture of the associated states and their evolution across a topological phase transition. They also study the topology in an interacting quantum system, which requires a new qubit architecture that allows for simultaneous control over every term in a two-‐qubit Hamiltonian. By exploring the parameter space of this Hamiltonian, they discover the emergence of an interaction-‐induced topological phase. This work establishes a powerful platform to study topological phenomena in quantum systems.

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Observation of chiral currents with ultracold atoms in bosonic ladders M. Atala, M. Aidelsburger, M. Lohse, J. T. Barreiro, B. Paredes, I. Bloch Nature Physics 10, 588–593 (2014)

The Meissner effect is the hallmark signature of a superconductor exposed to a magnetic field. For a type-‐II superconductor, full screening of the applied external field occurs up to a critical field. Below this value, the superconductor acts as a perfect diamagnet in the so-‐called Meissner phase. For fields above the critical value, however, the superconductor is not able to fully screen the applied field and an Abrikosov vortex lattice phase is formed in the system.

In their work, Atala and co-‐workers report on the observation of chiral Meissner currents in bosonic ladders exposed to a strong artificial magnetic field. By suddenly decoupling the individual ladders and projecting into isolated double wells, they are able to measure the currents on each side of the ladder. For large coupling strengths along the rungs of the ladder, they find a saturated maximum chiral current, which is analogous to the surface currents in the Meissner effect. Below a critical inter-‐leg coupling strength, the chiral current decreases in good agreement with the expectations for a vortex lattice phase. This work opens the path to exploring interacting particles in low dimensions exposed to a uniform magnetic field.

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Non-‐local propagation of correlations in quantum systems with long-‐range interactions P. Richerme, Z.-‐X. Gong, A. Lee, C. Senko, J. Smith, M. Foss-‐Feig, S. Michalakis, A. V. Gorshkov, C. Monroe Nature 511, 198-‐201 (2014);

Quasiparticle engineering and entanglement propagation in a quantum many-‐body system P. Jurcevic, B. P. Lanyon, P. Hauke, C. Hempel, P. Zoller, R. Blatt, C. F. Roos Nature 511, 202-‐205 (2014)

The maximum speed with which information can propagate in a quantum many-‐body system directly affects how quickly distant parts of the system can become correlated. For systems with only short-‐range interactions, Lieb and Robinson derived a constant-‐velocity bound that limits correlations to within a linear effective ‘light cone’. However, little is known about the propagation speed in systems with long-‐range interactions, since analytic solutions rarely exist and the best long-‐range bound is too loose to accurately describe the relevant dynamical timescales for any known spin model.

Both of these works report the experimental investigation using trapped ions of quantum correlation propagation in systems with long-‐range interactions. In the first work, Richerme and co-‐workers apply a variable-‐range Ising spin chain Hamiltonian and a variable-‐range XY spin chain Hamiltonian to a far-‐from-‐equilibrium quantum many-‐body system and observe its time evolution. For several different interaction ranges, they determine the spatial and time-‐dependent correlations, extract the shape of the light cone and measure the velocity with which correlations propagate through the system. In the second work, Jurcevic and co-‐workers implement a similar experiment. Using the ability to tune the interaction range in trapped ion systems, they also study the information propagation in systems with long-‐range interactions.

These two works open the possibility for studying a wide range of new many-‐body dynamics of interacting quantum systems.

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Two-‐dimensional lattice gauge theories with superconducting quantum circuits, D. Marcos, P. Widmer, E. Rico, M. Hafezi, P. Rabl, U.-‐J. Wiese, P. Zoller Annals of Physics 351, 634-‐654 (2014)

Despite significant progress and efforts, lattice gauge theories remain to be challenging to be simulated on classical computers. A quantum simulator of U(1) lattice gauge theories can however be implemented with superconducting circuits. This allows, for instance, the investigation of confined and deconfined phases in quantum link models, and of valence bond solid and spin liquid phases in quantum dimer models.

In their work, Marcos and co-‐workers, show how state-‐of-‐the-‐art superconducting technology allows one to simulate these phenomena in relatively small circuit lattices. By exploiting the strong non-‐linear couplings between quantized excitations emerging when superconducting qubits are coupled, they show how to engineer gauge invariant Hamiltonians, including ring-‐exchange and four-‐body Ising interactions. They also demonstrate that, despite the presence of decoherence and disorder effects, minimal circuit instances suffice to investigate properties such as the dynamics of electric flux strings or signaling confinement in gauge invariant field theories. The experimental realization of


these models in larger superconducting circuits could address open questions beyond current computational capability.

Task 2.4 Sustainability

The position document “Quantum Technologies in H2020” (attachment A), represents a very good starting point for the development of a white paper for sustainability, as it already expresses a broad consensus of the community on assessing both the state-‐of-‐the-‐art and the future directions of the different subareas. We are currently working on an expanded version following the restructuring of the Virtual Institutes that we just completed (see the description of Task 2.2.b).

As far as P6 CHALMERS is concerned, it should be noticed that during Y2 it has worked towards assessing the European competiveness in the Quantum Technologies area, and the resources needed to lead the development. Its conclusions are illustrated by the contribution it submitted independently to the aforementioned FET public consultation procedure, and reported in Attachment D. This material will be further developed and fully integrated with novel material and views thus representing valuable input into the process of expanding the document “Quantum Technologies in H2020” (Attachment A), to be carried out during Y3 by the new QUTE-‐EUROPE Virtual Institutes and Facilities previously described. In particular, CHALMERS focus on monitoring of the developments in superconducting circuits will provide material to the VI of Quantum Computing, the VI of Quantum Simulation and the VF on Quantum Engineering, in the preparation of the final version of both the QIPC Strategic Report as well as the White Paper on sustainability.

Finally, on this task, a number of activities of partners FBK/UULM addressing the sustainability of the entire area should be reported. These have materialized in the following meetings:

• 15.01.2015 – Meeting QUTE-‐EUROPE in Paris (follow up new Virtual Institute). This strategic meeting was planned in order to implement the modification to the virtual institutes and virtual facilities, with the aim of creating a wider and solid basis, the foundation, of possible future participation to project call such for instance a flagship.

• 18-‐19.01.2014 Quantum Lunch at the European Parliament, Organised by TUDELFT (Quantum Engineering). This event was organised by TUDELFT, recently involved in the structure of the virtual institutes and virtual Facilities with the aim of raising awareness about the relevance of QT, especially for future perspective and in order to keep up with the challenges coming from USA and China (which has been pushing on quantum technology with tremendous strength)

• 20.10.2014-‐ QUTE EUROPE meeting at MPQ. This meeting was a prosecution of a year-‐long effort to steer the community toward a more solid and inclusive structure, expanding the existing virtual institute and incorporating also Virtual Facilities on Quantum Engineering and Quantum Control

• 24.08.2014 – Business lunch with Dr. K. Kirby, CEO of the American Physical Society, for Collaboration with APS on Quantum Technologies. The discussion during this meeting revolved around a possible collaboration with the APS for possible development of the QT field.

• 09-‐11.07.2014 – Meeting on Quantum Technologies for Photonics with DG CNECT this meeting was part of the effort to bridging the QT topics also within the field of Photonics: QT, in fact, has opened a collaboration with the Photonics 21 platform.


• 21-‐22-‐05.2014 – CHISTERA meeting. The aim of this meeting was to explore the possibilities for the QT community to take part to long term co-‐funded projects, such as those like ERANET and ERANET Cofund.

• 29.04.2014 – FET flagship Consultation: this consultation, promoted by the EC, was aimed to explore the feasibility of a QT flagship project. The aim of such flagship would be to coordinate the whole community at large, possibly in a more inclusive way that has been done so far. Prof Calarco took part as member of the the European Academy of Sciences, where he is actively promoting QT

Attachments: Annex A: Quantum Technologies in H2020 Annex B: Virtual Institute Online meeting Annex C: QUTE-‐EUROPE meeting Annex D: Chalmers contribution to the FET online consultation


ANNEX A

Quantum technologies involve the control and manipulation of quantum systems to achieve results not possible with classical matter. Naively, they can be seen just as the next step on from nanotechnology while still following traditional paradigms. However, quantum technologies give much more than this as they transfer technological applications to a different physical framework where devices are described by quantum laws. All technologies derive their power and their limitations from the laws of physics. Thus, bringing technology to a new and broader physical framework can provide fundamentally new capabilities. And in fact, these quantum technologies offer much more than cramming more and more bits to silicon and multiplying the clock–speed of the ubiquitous microprocessors: they support entirely new modes of computation with qualitatively new and powerful algorithms based on quantum principles, that do not have any classical analogues; they also offer provably secure communications, simulation capabilities unattainable with classical processors and sensors and clocks with unprecedented sensitivity and accuracy.

The present document provides an overview on the main advances in the last years in quantum technologies and identifies game-‐changing directions for future research. Moreover, it discusses how all this research effort can be incorporated within future proactive initiatives to be included in the next FET work programme for 2016 and 2017.

Since many years, quantum technologies have experienced impressive progress and gained a clear European dimension. There are already several important on-‐going national efforts, such as the recent UK investment of £270M. Yet, a comprehensive European synergy is essential for the full development of the field. From a scientific point of view, a comparably high level of synergy needs to be maintained between the fundamental and the application-‐oriented side of quantum technology research, according to the approach that FET has followed in this field since its inception.

The framework for interaction and coordination with the scientific branches of the EU research community in quantum technologies is structured around a set of five Virtual Institutes (VIs): the Virtual Institute of Quantum Communication, the Virtual Institute of Quantum Computation, the Virtual Institute of Quantum Information Sciences, the Virtual Institute of Quantum Simulation and the Virtual Institute of Quantum Metrology, Sensing, and Imaging. Each VI unites some prominent experts in the corresponding field, providing a contact point for consultation and feedback in the relevant areas. The different VIs have partially overlapping research agendas to facilitate close collaborations, complementing rather than duplicating each other. This document is structured around the same five areas and has been prepared in collaboration with the Directors and Executive

Quantum Technologies in H2020


Secretaries of all the VIs. For each of the areas, it describes the main objectives, the state of the art and the future challenges.

Quantum Communication

Objectives: Quantum communication is the art of transferring a quantum state from one location to another; in this way information, or resources such as entanglement, can be distributed among different locations. From an application point of view, a major interest has been focused on Quantum Key Distribution (QKD), as this offers a provably secure way to establish a confidential key between distributed partners. This has the potential to solve long-‐standing and central security issues in our information based society as well as emerging problems associated with long term secure storage (e.g. for health records and infrastructure) and will be critical for the secure operation of applications involving the Internet of Things (IoT) and cloud networking.

State of the art: In the last years the field has seen enormous progress, as QKD systems have gone from table-‐top experiments to compact and autonomous systems and now a growing commercial market. More generally there has been an explosion in the number of groups active in the field working on increasingly diverse physical systems. Quantum memories and interfaces have moved from theory to a wide range of proof-‐of-‐principle demonstrations with encouraging results for the future. Conceptually, the idea of device independent quantum information processing made its appearance and has already started to find experimentally feasible applications. While the realisation of basic quantum communication technologies is becoming more routine in the laboratory, non-‐trivial problems emerge in high-‐bit-‐rate systems and long-‐distance applications as we interface the different technologies and as the network complexity increases.

Future directions: One of the emerging areas of interest for quantum communication schemes is in connecting the nodes within quantum simulators, which can either be all located in the one lab, or more interestingly, in distributed scenarios -‐ the tools from quantum communication playing the role of wiring circuits for these quantum computers. A particular application is a network of entangled clocks providing precise and secure world time reference. While there remain many challenges for proof-‐of-‐principle laboratory demonstrations, the transition to deployment in real-‐world environments defines a new set of challenges in the quantum information domain. The issues of scale, range, reliability, and robustness that are critical in this transition cannot be resolved by incremental improvements, but rather need to be addressed by making them the focal point of the research and technology development agenda as we work towards a quantum internet. To succeed, this needs to target the underlying technologies, ranging from fundamental aspects of engineering quantum systems to integrating quantum and classical, e.g. fast (classical) opto-‐electrical systems, as well as the end-‐user applications themselves.

In particular the following need to be addressed:

Quantum networks, beyond point-‐to-‐point, exploring novel protocols, possibly hybrid (continuous-‐variable and discrete) systems. Quantum repeater concepts will also be critical in the context of computation and simulation, both for short distance scales (local) or large (distributed) processing systems.

Deterministic and scalable technologies involving on-‐demand photonic sources, or heralded sources with quantum memories, including quantum memories with multimode capacity.

Interfaces allowing for the coherent transduction of quantum states between different physical systems.


The synchronisation and stabilisation of distributed quantum systems and their characterisation – in particular, their quantification with local measurements.

Device-‐independent quantum information processing needs to be further investigated and ways to move from purely theoretical concepts to more practical scenarios will be highly relevant. In particular, addressing both QKD and quantum random number generation and providing a new perspective with the potential to also minimise security assumptions and hence simplify the security of real-‐world quantum communication.

Systems that exploit increased complexity, e.g. using integrated quantum photonics, which would allow new functionality and protocols in quantum networking.

Quantum Computation

Objectives: A quantum computer is a device that harnesses some of the basic laws of quantum mechanics in order to solve problems in more efficient ways than classical (standard) computers. The main objective in the field of quantum computation is to build such a device. Other objectives include the development of quantum algorithms to solve specific problems, and the creation of interfaces between quantum computers and communication systems. The construction of a quantum computer with thousands of quantum bits would have tremendous consequences on the security in communications (like the internet), by breaking most of everyday used cryptography. It would also allow us to solve certain problems that the most powerful super computers are not able to solve now or in the near future, and possibly never; in particular, those dealing with quantum many-‐body systems, as they appear in different fields of physics, chemistry, and material science.

State of the art: We already know that the basic principles of quantum computation are correct and there is no fundamental obstacle in constructing such a powerful machine. The basic building blocks of a quantum computer have been demonstrated with many different technologies, including trapped ions, neutral atoms, photons, NV-‐centers in diamonds, quantum dots, and superconducting devices. Small prototypes have been built using some of those technologies, and some of the quantum algorithms have been demonstrated. The most advanced technologies at the moment are trapped ions and superconducting qubits. With the first one, coherent control has been achieved with up to 15 qubits. Although the control of the latter is still not at the level of the first, it has the potentiality of being scaled up much more easily. With both technologies, proof-‐of-‐principle experiments on quantum error correction have been carried out.

Future directions: Despite the strong efforts devoted by many scientists during the last years, the objective of building a quantum computer remains as a central challenge in science. The main obstacle to build a quantum computer is the presence of decoherence, i.e., undesired interactions between the computer’s constituents and the environment. Standard isolation is not a valid solution, since it seems impossible to reach the levels of isolation that are required in large computations. Therefore, the construction of such a device will require the use of quantum error correction techniques. It is not clear, however, which (already or not yet existing) technology will be optimally suited for the implementation of such techniques in a scalable way and/or in distributed settings. On a different note, we only know a limited class of problems where a quantum computer could overcome the limitations of classical ones, and thus theoretical studies for applications of such devices need to be further pursued.

Some specific future directions of research include:


Further development of all current technologies to understand their limitations and find ways around them.

Assessment of the capabilities of different technologies for being scaled up. Optimization of the performance of error correcting codes, by both increasing the error

threshold and decreasing the overhead of required qubits. Investigation of new ways of performing quantum computation, in particular based on self-‐

correcting codes (as they appear in topological systems). Development of new quantum algorithms and search for problems where quantum

computers will be required. Development of quantum complexity theory and its application to many body physics. Building interfaces between quantum computers and communication systems. Development of quantum-‐proof cryptography to achieve forward-‐in-‐time security against

possible future decryption (by quantum computers) of encrypted stored data.

Quantum Information Sciences

Objectives: The development of quantum technologies has been driven by theoretical work of scientists working on the boundary between Physics, Computer Science, Mathematics, and Information Theory. In the early stages of this development, theoretical work has often been far ahead of experimental realization of these ideas. At the same time, theory has provided a number of proposals of how to implement basic ideas and concepts from quantum information in specific physical systems. These ideas are now forming the basis for successful experimental work in the laboratory, driving forward the development of tools that will in turn form the basis for all future technologies which employ, control and manipulate matter and radiation at the quantum level.

State of the art: in recent years, novel theoretical ideas have been proposed, extending the range of applicability of quantum information protocols. The novel scenario of device-‐independent quantum information processing has emerged, where protocols are defined independently of the inner working of the devices used in the implementation. This new approach has led to self-‐certified schemes for QKD and randomness generation. A strong theoretical effort has opened quantum simulation to quantum field theories and quantum chemistry. From a purely information theory point of view, non-‐additivity effects of channel capacities with no classical analogue have been proven. Finally, quantum information theory has established strong bridges with other fields, such as condensed matter, quantum thermodynamics, biology or quantum gravity. The study of topological systems for quantum information purposes, the development of novel numerical methods for the classical simulation of many-‐body quantum systems, the study of Hamiltonian complexity or, more recently, the use of quantum information techniques for a better understanding of the physics of black holes, as well as applications in mathematics and computer science, are examples of these synergies.

Future directions: the impressive experimental progress in controlling quantum particles has brought the field to a regime where experimental setups can hardly be simulated in existing classical computing devices. The design of methods to estimate, control and certify these complex setups is essential for the development of the field. Also, we expect quantum information theory to extend and strengthen its applicability to other fields, providing new insights in quantum thermodynamics, many-‐body physics or quantum gravity. The recent device-‐independent scenario, in which protocols are defined independently of the inner working of the devices, also offers promising perspectives, especially for cryptographic applications.


Relevant research directions for the next years include:

Methods for the reconstruction and estimation of complex quantum states or channels beyond tomography protocols, which are as hard as simulating a quantum system classically.

Methods for the certification and validation of quantum processes; benchmarking of purely quantum effects with no classical analogue.

Methods for error correction beyond quantum computation and study of their application to quantum simulation, communication or sensing.

Methods for the control of complex quantum setups Development of device-‐independent solutions: novel protocols, general framework for

security analysis in this approach or feasible proposals for their experimental realization. Novel applications of quantum information concepts in other fields, such as

thermodynamics, many-‐body systems, mathematics, computer science, biology, quantum chemistry, high-‐energy physics or quantum gravity.

Development of undecidability theory.

Quantum Simulation

Objectives: Quantum simulation uses controllable quantum systems to investigate the properties of other complex quantum systems, and can tackle problems that are beyond the computational capability of any classical computer. Initial experimental and theoretical work has been mainly directed towards the quantum simulation of condensed matter systems, such as bosonic or fermionic particles in lattices, but more recent work also encompasses such diverse fields as quantum field theory, cosmology and high-‐energy physics.

State of the art: Experimental platforms for quantum simulation comprise ultracold atomic and molecular quantum gases, ion traps, polariton condensates, circuit-‐based cavity quantum electrodynamics and arrays of quantum dots or Josephson junctions. All of these platforms aim to explore the potential of quantum simulations for different fields of science. The first demonstrations of quantum simulation were performed on ultra-‐cold atoms. In this platform, the quantum-‐gas microscope technique has opened up novel possibilities to probe and manipulate cold-‐atom quantum simulators at the single-‐particle level. For trapped ions, the extraordinary level of control of motional and internal quantum states has enabled for example the realization of a digital quantum simulator, and analogue quantum simulation of different spin systems. Recently, also solid-‐state systems like coupled arrays of cavities or superconducting qubit arrays, or arrays of defect centres, are being explored for quantum simulation purposes.

Future directions: The challenges of the science of quantum simulation can be divided into four categories that need to be addressed:

Novel manipulation and detection schemes for quantum many-‐body systems to further improve the controllability of artificial quantum matter realized for quantum simulation purposes. This includes improving fidelities of present preparation schemes, as well a devising novel measurement and control techniques and also include identifying completely novel systems for quantum simulations.

Extend the reach of quantum simulations into other fields of science, e.g. quantum field theories in high-‐energy physics, nuclear physics, cosmology (simulation of non-‐equilibrium dynamics), biology, chemistry and material science.

Novel strategies toward lower temperatures and entropies of many-‐body systems. This will allow exploring novel quantum phases of matter that could find important impact in metrology (e.g. atomic clocks), quantum computing or material science.


Novel strategies for the verification of quantum simulations, studying how finite temperature errors and imperfections in implementations of couplings affect the resulting many-‐body state.

Quantum Metrology, Sensing, and Imaging

Objectives: Specifically quantum phenomena such as coherence and entanglement can be exploited to develop new modes of measurements, sensing, and imaging that offer unprecedented levels of precision, spatial and temporal resolution, and possibly auto-‐compensation against certain environmental factors, such as dispersion. These promising applications require development of techniques that will be robust against noise and imperfections to be deployed in real-‐world scenarios. Quantum technologies will benefit in particular time and frequency standards, light-‐based calibration, gravitometry, magnetometry, accelerometry, including the prospects of offering new medical diagnostic tools.

State of the art: Reaching quantum-‐enhanced precision beyond standard quantum limits in metrology relies on generating non-‐classical collective states of atoms and non-‐classical multi-‐photon states of light. Extensive effort has been dedicated to these goals with proof-‐of-‐principle demonstrations in the atomic domain and the first squeezed-‐light-‐enhanced operation of a gravitational wave detector with practical suppression of vacuum fluctuations. Novel concepts, such as systems with an effective negative mass or negative frequency have been shown to be capable of providing magnetometry with virtually unlimited sensitivity. Possibilities to define new frequency standards have been explored with the readout based on quantum logic techniques borrowed directly from the field of quantum computing and with entangled atoms providing ultimate quantum sensitivity. Enormous progress has been made on single photon sources, both deterministic and heralded, that can be used for optical calibration as well as a building block for photonic quantum communication and computing. Artificial atoms (such as nitrogen vacancy centers) have been investigated as ultraprecise sensors e.g. in magnetometry.

Future directions: Original techniques are needed to make quantum-‐enhanced metrology and sensing deployable in non-‐laboratory environments. Because of the wide range of prospective applications and their specificity, a broad range of physical platforms needs to be considered, including (but not limited to) trapped ions, ultra-‐cold atoms and room-‐temperature atomic vapours, artificial systems such as quantum dots and defect centers, as well as all-‐optical set-‐ups based e.g. on nonlinear optical interactions. Thorough theoretical analysis of noise mechanisms is needed, leading to feasible proposals that will be subsequently implemented to realize quantum-‐enhanced strategies. In particular the following need to be addressed:

Novel sources of non-‐classical radiation and methods to engineer quantum states of matter are required to attain quantum-‐enhanced operation.

Develop detection schemes that are optimized with respect to extracting relevant information from physical systems, with optimization criteria selected for specific applications. These techniques may find applications in other photonic technologies, e.g. increasing transmission rates in optical communication.

Micro-‐ and nanofabrication of quantum sensors including integration with fiber networks Development of hybrid quantum sensors that use optimal quantum interfaces for

transduction of signals across the electro-‐magnetic radiation spectrum.


Compact solutions for quantum imaging, allowing for the interconversion of detected frequencies including preservation of coherence, as well as quantum ranging and timing that can suppress the spatial/temporal spread of transmitted signals.

Implementation of entanglement assisted atom clocks Study of the performance of quantum sensing protocols in realistic regimes including noise

and losses. Extend the reach of quantum sensing and metrology into other fields of science to uncover

novel natural phenomena, e.g. biology, fundamental physics, high-‐energy physics, quantum gravity.

Global perspective and role in the work programme

While the previous presentation has been structured along the different VI’s, the field of quantum technologies has to proceed as a coherent and unified research effort. Indeed, many synergies among the different research directions are expected and essential to attain the previous objectives. To name just a couple of illustrative examples, detection and state-‐preparation techniques developed in the context of quantum communication will find an application in sensing scenarios, and error-‐correction techniques developed in the context of quantum computation will be needed for the certification of quantum simulations. In this sense, the role of basic science and theoretical new ideas is essential, as new disruptive theoretical proposals can significantly boost many of the previous promising applications of quantum technologies. Progress in all of these areas is reliant on fundamental research to improve and find new enabling technologies and concepts.

Quantum technologies are already present in the current work programme. Recently, there has been a proactive call on quantum simulation. There are also explicit mentions to quantum concepts in the work programme: in ICT 25 -‐ 2015: Generic micro-‐ and nano-‐electronic technologies, projects may include activities “related to modelling and simulation: e.g. quantum and atomic scale effects” or study “new computing paradigms like quantum computing”; in ICT 26 -‐ 2014: Photonics KET, new device concepts “based on quantum optics or quantum technologies” are mentioned in the context of disruptive sensing technologies; finally, in ICT 32-‐2014: Cybersecurity, Trustworthy ICT, post-‐quantum key distribution and several aspects of QKD appear.

In our vision, the framework programme for the next years is a key funding mechanism to support and unite all the previous research activities, from basic theoretical research to industrial applications. In this sense, we expect quantum technologies to gain an even more visible role in future research funding in Europe. A proactive call on quantum technologies, complementary to the recent one on quantum simulations, is timely and can help in bringing the developments described above much closer to applications. As mentioned, theoretical ideas should remain visible in the programme, as we are still far from understanding all that quantum properties can offer for technological purposes. Finally, we also expect quantum aspects to increase their relevance in the photonics, security and nano-‐technologies programs. For instance, the possibility of self-‐certified protocols using device-‐independent techniques brings cryptographic applications to a significantly stronger level of security where a much lower level of trust is needed on the provider. Also, new photonic devices operating at the quantum scale will emerge from the research effort in photonics and nano-‐technologies. In this sense, calls in these programs parallel to those in FET can be expected to deliver a major synergy effect.

Let us conclude by mentioning that bridging the gap between blue-‐sky research and applications will take time and several iterations. It should also be understood at this early stage of researching


quantum technologies that in all likelihood there will not be one single solution, but many, on the way to developing this key enabling technology of the 21st century and to build a quantum industry.

This memorandum is endorsed by

Nicolas Gisin (Director, VI of Quantum Communication), Rob Thew (Executive Secretary, VI of Quantum Communication), Juan-‐Ignacio Cirac (Director, VI of Quantum Computation), M. Wolf (Executive Secretary, VI of Quantum Computation), Peter Zoller (Director, VI of Quantum Information Science), Antonio Acin (Executive Secretary, VI of Quantum Information Science), Immanuel Bloch (Director, VI of Quantum Simulation), Stefan Kuhr (Executive Secretary, VI of Quantum Simulation), Ian Walmsley (Director, VI of Quantum Metrology, Sensing, and Imaging), Konrad Banaszek (Executive Secretary, VI of Quantum Metrology, Sensing, and Imaging); QUTE-‐EUROPE External Advisory Board: Rainer Blatt, Harry Buhrman, Nicolas Cerf, Artur Ekert, Atac Imamoglu, Massimo Inguscio, Sir Peter Knight, Leo Kouwenhoven, Maciej Lewenstein, Martin Plenio, Eugene Polzik, Gerhard Rempe, Reinhard Werner, Anton Zeilinger; Tommaso Calarco (QUTE-‐EUROPE Roadmap coordinator), Daniele Binosi (QUTE-‐EUROPE Executive Secretary)


Annex B

Virtual Institute Online meeting Date: 16.09.2014, from 14:00 to 16:00 Place: Virtual meeting Participants:

1. Acin Antonio 2. Banaszek Konrad 3. Binosi Daniele 4. Blatt Rainer 5. Burhman Harry 6. Buzek Vladimir 7. Calarco Tommaso 8. Cerf Nicolas 9. Cirac Ignacio 10. Gisin Nicolas 11. Kouwenhoven Leo 12. Kurh Stefan 13. Lewenstein Maciej 14. Polzik Eugene 15. Steffen Glaser 16. Thew Rob 17. Walmsley Ian 18. Werner Reinhard 19. Willhelm Frank 20. Zeiliger Anton 21. Ziman Mario 22. Zoller Peter

Agenda:

Presentation of the Quantum Control VI Presentation of the Quantum Engineering VI Vote on the new virtual institute

Minutes:

The meeting was called since in the previous year the need of a restructuring of the Virtual Institutes emerged as necessary in order to better address the constant evolution of the Quantum Technology community. The meeting started with the presentation of the possible structure of the virtual institute of Quantum Control. After a brief discussion, the second new virtual institute, Quantum Engineering was presented. To this followed a discussion about how to properly integrate these new insititutes in the pre-‐existing structure. One of the main point under discussion was how to properly mark the difference in scope between the new and the old institutes. More specifically, one of the


suggestions was to have the Quantum Engineering Institute as an overarching structure, supposedly embracing all the other institutes, thus providing them with the relevant engineering expertise. Albeit it was acknowledged that it was relevant to have such an institute, especially in order to represent area of the community that were considered underrepresented, there was not a general consensus on how to proceed in these sense. Specifically, a fear of an excessive “virtual institute proliferation” was pointed out. Among the suggestions made to avoid this issue, there was also the proposal to merge the two new Virtual institutes into a single one. The idea however was discarded.

The Chairman, Prof. Tommaso Calarco called for an explorative vote to see if a consensus was reached at least on the creation of the two new virtual institutes. However, while the Quantum Control structure displayed a large number of positive votes, the same was not true for the Quantum Engineering institute. Many of those who expressed themselves against it, stated that this was due to the fact that it was still not clear how this Virtual Institute would place itself with respect to the Quantum Control one.

Given this fact, it was decided that a restricted physical meeting was needed to clear all the open question. Consequently, it was decided that the QUTE-‐EUROPE steering committee, with the addition of some representative from the involved part of the community, would be an adequate body to decide over this matter.


Annex C

QUTE-‐EUROPE meeting

Date: 20.10.2014, from 10:30 to 16:30 Place: Max Planck Institute for Quantum Optics (Garching, Munich, DE) Participants:

1. Acin Antonio, 2. Binosi Daniele (video conference contribution), 3. Blatt Rainer (video conference contribution), 4. Bloch Immanuel, 5. Calarco Tommaso, 6. Cirac Ignacio, 7. Esteve Daniel, 8. Gisin Nicolas, 9. Glaser Steffen, 10. Inguscio, Massimo, 11. Kouwenhoven Leo, 12. Polzik Eugene, 13. Versleijen Anouschka, 14. Walmsley Ian (video conference contribution) 15. Wrachtrup Jörg, 16. Zoller Peter (video conference contribution),

Agenda:

Structuring the Field of Quantum Technologies at European Level: Quantum Clusters and Virtual Institute

Involving National Funding Organisations Updating the QT whitepaper and Roadmap.

Minutes:

This meeting was a continuation of the virtual meeting of the 17th of September. The meeting saw as participants the QUTE-‐Europe steering committee with some additional invited experts representing different parts of the community.

The first part of the discussion revolved around the future structure of the Virtual Institute in order to broaden the scope and cover rapidly growing areas of the Quantum Technologies field. During the meeting, the need for a virtual institute for Quantum Engineering and for Quantum Control, was re-‐asserted. From this point the discussion revolved around the possible way to integrate these new institutes “organic” with the pre-‐existing one. A structure similar to the one already into place was selected with the old institutes acting as “vertical structures”, whereas the new ones would be of the horizontal type instead, having (due to their cross-‐disciplinal nature) points of contact with all the


existing ones. This difference is reflected also in the name, which has been chosen to be Virtual Facilities. The Virtual Institutes would also undergo a large restructuring. The first issue that needed to be addressed was the limited representation of the Solid State community within them. The assembly decided that it would be wise to expand the number of people directly involved in each VIs. In particular, it was decided that, along with the Director and the Executive Secretary each Institute should have from 2 to 5 additional members, in order to better represent all the different areas of the community. Finally, some of the Director and Executive Secretary were also shifted from one virtual institute to another.

The new directorships suggested were the following:

Coordinator A. Acin Virtual Institute Computation Simulation Communication Sensing Theory

Director D. Esteve I. Bloch N. Gisin I. Walmsley I. Cirac Executive Secretary

A. Wallraff S. Kuhr R. Thew K.Banaszek M. Wolf

Virtual Facility Engineering Control

C. Marcus S. Glaser J. Morton F. Wilhelm

As far as the new VI members were concerned, it was decided that they would be nominated via an online pool. The election of the Directors of the Virtual Facilities, their executive secretaries and members, were also postponed to a future meeting since the matter required some additional consultation.

Finally, given all the structural changes, an update to the QT White Paper and to the Roadmap, was considered necessary, in order to better reflect the new structure. The Virtual Institute were tasked to come up with updated information concerning the part of their work connected with the aforementioned documents, and possibly consults with the new members as soon as they got elected.

The final Part was dedicated to the discussion of future direction of the Community. On the table it was presented the need to address the issue generated by the google announcement of the development of a Quantum computer (which still leaves a lot of doubt) and what this announce means for the future of Quantum technology. Some of the attendee stressed the need to step up on the technological side.

The attendee openly discussed also the opportunity of a flagship and the possible reception of such proposal from the Quantum Technology community. In this sense, other options were discussed to, such as the chances for a QT project in a possible ERANET call, as well as the possible contact with the venture capital world.


Annex D

Chalmers contribution to the FET online consultation

Quantum computing research is progressing fast on a global scale and starts making a transition towards engineering and industry outside Europe. Globally, the field of Quantum Technologies (QT) is entering a stage where large resources are put into engineering of devices and systems in a quest for ground-‐breaking applications in quantum computing, simulation, and communication. The competition is becoming fierce, and major resources are invested in USA, Canada and Japan in powerful collaborations to achieve breakthroughs in fault-‐tolerant computing. The concept of "The European Dimension", i.e. fairly loose EU collaborations without adequate funding at the R&D level, is no longer enough to stay competitive in the QT field. Europe is already falling behind.

Superconducting circuits (specifically transmon-‐cQED with coherence times in the 100 microseconds range) are now being scaled up to systems with 10-‐20 qubits and beyond. Europe is in the very frontline when it comes to fabrication and operation of small experimental systems, aiming for 10 qubits within 1-‐2 years. However, the next step, scaling up to 20+ qubits will involve an engineering effort requiring orders of magnitude larger resources than presently available. Moreover, it will require training of a new kind of engineers, and it must involve industrial fabrication.

In Europe we must therefore urgently face the question of how to create a sustainable development of quantum information processing (QIP) and communication, and how to provide the resources for scaling up QT platforms, both solid-‐state and AMO ones.

To this end it is necessary to realise that we are ultimately talking about focused efforts at the level of a flagship -‐ a QT Flagship -‐ with strong commitment from industry and national funding agencies. A limited proactive programme during 2016-‐17 can certainly contribute to many exciting achievements, but cannot define a > 10-‐year QT strategy and provide the corresponding funding -‐ this will take a QT Flagship, or a comparable effort. A QT Flagship will no doubt be needed in order to be able to engage and develop European industry and to create a unified approach involving national funding agencies. A QT Flagship will also be able to include and integrate a variety of fundamental quantum research activites in purposeful way.

An important aspect of QT is high-‐performance computing (HPC). It is obvious that running quantum computers and simulators will involve classical frontends and processing, and in the future, quantum processors will most likely in practice be accelerators embedded in classical HPC (cHPC) systems. Nevertheless, for efficiency, the classical integration needed should be developed within (or directed by) a QT Flagship, and there is no clear foundation, within the foreseeable future, for QT-‐cHPC project integration.

New computing paradigms are required for information processing including, for example, neuromorphic computing, quantum computing, chemical and molecular computing, quantum computing by molecular spin clusters and bio-‐inspired computing, among others. Solid-‐state quantum computing and neuromorphic computing could become embedded in digital environments


via digital-‐analogue hardware and software interfaces. The target would be to create useful hybrid systems capable of adaptive learning.

Actually, recent QIP development makes use of quantum neuromorphic algorithms (classifiers) for machine learning involving optimisation and pattern recognition in big (quantum) data bases. This underlines that a QT flagship needs to incorporate a broad field of computer science.

Finally there is the issue of the D-‐Wave Systems company: D-‐Wave has developed several systems of 512 superconducting qubits used for quantum annealing (analog computing; optimisation), a 1000 qubit system is in the pipeline, and 2000 qubits in the near future. D-‐Wave is supported by venture capital, Google, NASA, NSA, Lockheed-‐Martin, .... and has sold 2 machines to Lockheed-‐Martin (placed at USC) and to NASA-‐Ames. Google is developing software for optimisation, and testing the machine. The machines currently basically do not outperform classical PC-‐machines with optimized annealing software, but the superconducting technology is groundbreaking, and the scaling-‐up is "easy", because the qubit arrays are not coherent. (See also the comments by Daniel Esteve). Time will show whether the D-‐Wave machines are worth the money. The bottom line is that D-‐Wave represents a kind of entrepreneurship that simply does not exist in Europe, but efforts at that scale, or larger, are essential for QT-‐Europe to prevail. A QT-‐flagship would have to be the European way to go, because venture capital and industry involvement at the needed scale do not exist in Europe at the present time. It should be noted that D-‐Wave has worked during 10 years to reach its present level. In Europe, it seems that the EC and public funding must lead the way via a QT-‐flagship that then can develop the needed commitments and funding in a relatively short time.

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