quantum teleportation · 2017. 4. 12. · quantum information processing ii implementations:...

||Quantum Information Processing II Implementations: Quantum Teleportation

“Deterministic quantum teleportation with feed-forward in a solid state system”Steffen, Lars, et al. Nature 500.7462 (2013): 319-322.

Christoph Dlapa, Martin Stadler, Martin Woschank

03.04.2017

Quantum Teleportation


Introduction and Repetition• Why quantum teleportation

• Algorithm and Gates

Implementation of the Circuit

Results and Discussion

03.04.2017Christoph Dlapa, Martin Stadler, Martin Woschank 2

Outline

||Quantum Information Processing II Implementations: Quantum Teleportation 03.04.2017Christoph Dlapa, Martin Stadler, Martin Woschank 3

Why quantum teleportation?


Theory of Quantum Teleportation

sender

mediator

receiver

Transmission of

classical information


Implementation

sender

mediator

receiver


Multy-Qubit Cavity Bus (Transmission line)

Qubits coupled to/via oszillator• Similar to Cavidy-QED

• Large dipol, low dissipation

Strong coupling limit

Transition frequencies tunable through flux in qubit loop

Determine setup parameters through vacuum-Rabi-oszillations

Majer, J., et al. "Coupling superconducting qubits via a cavity bus." Nature 449.7161 (2007): 443-447.


Qubit-Qubit interaction through virtual photons

No direct interactions with the cavity

Quantum Non-Demolition (QND) Measurement of individual and joint qubit states


Two-Qubit Cavity Bus

Majer, J., et al. "Coupling superconducting qubits via a cavity bus." Nature 449.7161 (2007): 443-447.


Implementation of the Circuit


Implementation through the avoided crossing


CPHASE-Gate

DiCarlo, L., et al. "Demonstration of two-qubit algorithms with a superconducting quantum processor." Nature 460.7252 (2009): 240-244.


Ideal protocol:• Entangled pair between A and B

• Two-qubit measurement to identify all four Bell states

• Feed-forward of the classical information

Problem: space-like realization between sender and receiver


Protocol


Post-selected teleportation

Deterministic teleportation

Deterministic teleportation with feed-forward


Applied Methods


Implementation


Only need to distinguish one of the four Bell states

Through Josephson parametric amplifier measure whether Q1 is e.g. 00 (nooperations needed)

2nd Josephson parametric amplifier to read out Q3

To get process matrix χ00 four linearly indep input states will be used

(full process tomography)


Post-Selected teleportation protocol


Relation between process and output-state fidelity:•

d… dimensionality of states

Any Bell-state can be put into computational basis by applying π pulses toQ1 or Q2


Fidelities


Results and Discussion


Direction of view for image a

Extended Data Figure 2 | Characterization of the joint readout of Q1 and Q2

Deterministic readout



Extended Data Figure 1 | Pulse sequence of the teleportation protocol with feed-forward

Feedforward: ~500 ns !!!

Deterministic readout with feed-forward



Postselection process matrix


Deterministic readout process matrix


Deterministic readout with feed-forward process matrix


Post-selection



With feed-forward

Process matrices


Extended Data Table 1

Success probabilities for the joint readout

Extended Data Table 2

Process fidelities of the feed-forward pulses

Error sources



March 2014

Psi- created with F = 87 %

f = 1/250 s⁻¹

Average state fidelity

F = (77 ± 3) %

Readout fidelity

F = (96,3 ± 0,5) %


Comparision to quantum teleportation in NV-centers

May 2013

Phi created with F = 92 %

f = 10⁴ s⁻¹

Average state fidelity

F = (68,8 ± 0,5) %

Readout fidelity

F = (89,1 ± 0,5) %


Thank you for your attention!


Extended Data Figure 3 | Characterization of the output states

quantum teleportation · 2017. 4. 12. · quantum information processing ii implementations:...

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