‘Quantum’ in Padova, an historical overview

Cesare Barbieri

Emeritus of Astronomy

University of Padova

27/11/2017 Marostica 1

Two parallel Quantum programs

27/11/2017 Marostica 2

Quantum Astronomy (QA) Quantum Communications (QC) in Free Space

These activities were performed inside three Departments of our University (UPd)

Dept. of Physics and Astronomy (DFA)Dept. of Information Engineering (DEI)Dept. of Industrial Engineering (DII)

and by INAF Astronomical Observatory (OaPD)

Several researchers from other institutions in Italy and Europe were also involved, as detailed in the following.

The starting date for our ‘Quantum’ activities can be put at the very beginning of the XXI Century, along two lines of research:

The two avenues were expounded in a document at the completion of a study (financed by ESA and EC) named

HARRISON, from the name of the famous English clockmaker of the XVIII Century.

The HARRISON study for the utilization of the Time distributed by the GALILEO GNSS

27/11/2017 Marostica 3

Concluding Report:Quantum Astronomy

Quantum Key Distribution

Prof. Cesare BarbieriIng. Tommaso OcchipintiUniversity of Padova - Italy

Prof. Andrej Čadež

University of Ljubljana – Slovenia

At present, the QC activity in our University is entirely concentrated at the DEI (Gianfranco Cariolaro, Paolo Villoresi and collaborators). I’ll leave the QC topic to Prof. Anton Zeilinger, because the program enjoyed a continuous interaction with his group, so I’ll only present some slides of historical interest.

Our first QC experiments in a foggy Cima Ekar (Asiago) and above the roofs of Padova, from the tower of the

Specola to the DEI (approximately 2.5 km)

27/11/2017 4Marostica

Quantum Communications in free space

27/11/2017 5Marostica

Sending and receiving back single photons to geodetic satellites like LAGEOS First visit to ASI

station ‘Giuseppe Colombo’ in Matera Our warmest thanks to

Giuseppe ‘Pippo’ Bianco!

27/11/2017 Marostica 6

27/11/2017 7

Distribution of entangled Photons

Marostica

Distributing entangled photons to ground stations from the ISS

Canaries(ESA)

Matera(ASI)

Too bad ESA missed the opportunity,China came first!

A reference book

thanks Gianfranco per being with us today!

27/11/2017 Marostica 8

Quantum Astronomy

27/11/2017 Marostica 9

Main collaborators in Padova:

Giampiero Naletto, Tommaso Occhipinti, Ivan Capraro, Enrico Verroi, Paolo Zoccarato, Fabrizio Tamburini, Claudia Facchinetti, Sandro Centro, Mirco Zaccariotto (DEI, DFA, DII)Luca Zampieri, Massimo Calvani, Alexander Burtovoi, Michele Fiori (INAF OAPd)

with the collaboration of several other researchers from Italian and European institutions, some of them being here today (Andrea Possenti, Andrea Richichi, Andrea Mignani, Ivan Rech, Andrej Čadež, Andy Shearer, Gottfried Kanbach, Christian Gouiffes).

My deepest thanks to all of them!

Quanteye

27/11/2017 Marostica 10

The basic concepts were exposed in our study (QuantEYE, the ESO Quantum Eye, 2005) in the frame of the studies for the (then) 100m Overwhelmingly Large (OWL) telescope.

The study had two main goals:- Summarize the features of quantum optics

applicable to Astronomy with very large telescopes

- demonstrate the possibility to reach the picosecond time resolution and GHz photon rate needed to bring quantum optics concepts into the astronomical domain

From theory to reality: the key technological limitation was the detector

The most critical point, and driver for the design of QUANTEYE, was the selection of very fast, efficient and accurate photon counting detectors.

No detector on the market had all needed capabilities: In order to proceed, we choose SPADs (Single Photon Avalanche Diode Detectors) operating in Geiger mode, produced by MPD in Bolzano.

The main drawbacks of SPADs were the small dimensions (max 200 μm), the lack of CCD-like arrays, a 70 ns dead-time and a 1.5% after-pulsing.

To overcome both the SPAD limitations and the optical difficulty of coupling the pupil of a large telescope to very small detectors, the large telescope pupil was split into 10×10 sub-pupils, each of them focused on a single SPAD, giving a total of 100 distributed SPAD's. In such a way, a “sparse” SPAD array collecting all light and coping with the required very high count rate could be obtained.

The distributes array samples the telescope pupil, so that a system of 100 parallel smaller telescopes was realized, each one acting as a fast photometer.

1127/11/2017 Marostica

QuantEYE optical design

12

telescope pupil subdivision

27/11/2017 Marostica

Advantages of this optical design

• The global count rate is statistically increased by a factor N 2 with respect to the maximum count rate of a single SPAD. In the assumption of having N = 10 (100 SPAD's), the global count rate becomes 1 GHz;

• Simpler optical design;• Detector redundancy, easier maintenance;• By suitable cross-correlations of the detected signal,

a digital HBT intensity interferometer is realized among a large number of different sub-apertures across the full telescope pupil.

1327/11/2017 Marostica

After Quanteye

27/11/2017 Marostica 14

Capitalizing on Quanteye results, and in order to gain real experience for such highly unconventional concepts and instrumentation, we proposed to build single photon detectors for astronomical applications of Quantum Optics.

27/11/2017 Marostica 15

AQUEYE

Our proposal was accepted, and we built a prototype of QuantEye, named AQuEye (the Asiago Quantum Eye) for the 182 cm Copernicus Telescope at Asiago - Cima Ekar.

AquEYE optomechanical designThe light beam is divided in four parts by means of a pyramidal mirror. Each beam is then focused on its own SPAD by a 1:3 focal reducer made by a pair of doublets. Different filters can be inserted in each arm.

16

SPAD

filter

pyramidpyramid

pinhole

1:3 focal reducer

SPAD27/11/2017 Marostica

AquEYE Optomechanics

17

AFOSC focusPyramid

Focusing lenses

Filters

SPAD

27/11/2017 Marostica

The overall system

27/11/2017 18Marostica

A TDC board made by CAEN for CERN

The arrival time of each photon is stored separately for each channel, guaranteeing data integrity for the subsequent scientific investigations

Iqueye for the NTT

Thanks to the positive experience of AquEYE, it was decided to realize IquEYE, a more complex instrument for applications to 4m class telescopes, such as the ESO 3.5m NTT in La Silla (Chile), or the TNG or the WHT. The same basic optical solution of pupil splitting in 4 was maintained. A fifth SPAD was added to monitor sky variations

As with Aqueye, operation can be performed from a remote control room.1927/11/2017 Marostica

At the NTT

27/11/2017 Marostica 20

Seen here are: Giampiero Naletto and Enrico Verroi (optics), Tommaso Occhipinti, Ivan Capraro and Andrea Di Paola (electronics, software), Paolo Zoccarato (timing system), and myself.

From Aqueye to Aqueye+, the optical design

27/11/2017 Marostica 21

A major refurbishment of Aqueye has been performed, leading to Aqueye+: - a dedicated focal reducer, a field camera and a fifth SPAD which monitors the adjacent sky background have been implemented, - For future utilizations, an Optical Vortex coronagraphic module with l = 2 can be inserted, fed by a dichroic filter and very narrow filters. An adaptive optics module, whose deformable mirror is driven by the 4 SPADS, stabilizes the star on the tip of the coronagraph phase plate.

The present situation of Aqueye+

27/11/2017 Marostica 22

Aqueye+, still at the 1.8m Copernicus telescope, is in a dedicated, thermally controlled room. It is fed by an optical fibre coming from a mirror inserted at the entrance of the imaging spectrograph AFOSC.

This solution minimizes the operations for mounting Aqueye to the telescope.

Present status of Iqueye

27/11/2017 Marostica 23

Iqueye is back in Asiago, where it has been adapted to the 1.2m Galileo telescope at Pennar by means of an optical fibre, the same solution adopted for Aqueye+.

Sky Diameter on fiber core: 12.5 arsec

New lights in the Asiago sky

27/11/2017 Marostica 24

Aqueye and Iqueye have been used for a variety of astrophysical problems, from pulsar timing to X-ray binaries to lunar occultations, as will be detailed by Giampiero Naletto, Luca Zampieri, Andrej Čadež, Andrea Richichi and other speakers during this conference.As the subtitle of this brochure says:Research leading towards the future

New light for old telescopes

27/11/2017 Marostica 25

THANKS

27/11/2017 Marostica 26

Here we are today, ready for other exciting

observations!