Principal Investigator: Professor Nicolas Gisin
The Project
The University of Geneva is involved in a wide variety of projects within QAP. There are three principle research activities we contribute to QAP and these fall into the sub-projects: “Quantum Memories and Interfaces”; “Repeaters”; and “Theory”. We are also involved in the project management via the Training Committee as well as the Innovation Committee where we are promoting and attempting to facilitate quantum technology transfer from QAP to industry.
Quantum Memories and Interfaces
We are leading the sub-project “Quantum Memories and Interfaces” where we contribute to the research work-package “Rare-Earth-Ion Doped Solids” [6] as well as being WP leader for the “Comparison” WP which oversees the benchmarking and comparison for the wide variety of approaches to Quantum memories that are being investigated among many groups within QAP.
Theory
This work is being performed in collaboration with several other groups within QAP. There are several key aims for us: the realisation of QIPC in specific physical systems; to provide general tools for the analysis of existing, as well as new, Quantum Multi-user Protocols. We are interested in the analysis of Quantum Multi-user Protocols that are different from Quantum Key Distribution. The focus is on constructing new communication protocols providing results without analogue in Classical Information Theory and analysing those schemes that already give a significant improvement over their classical counter-parts. A special emphasis will be given to multi-partite entanglement.
Repeaters
We are involved in several of the work-packages in this project as we develop sources for quantum communication as well as how and what sort of quantum channels can be used and how these can be optimised.
The University of Geneva leads the WP “Long distance fibre optic relays and purification”. Quantum communication protocols require the distribution of entanglement between separate locations with high fidelity. The transmission of quantum information will inevitably be limited by decoherence over any quantum channel (communication link). Amplification and reshaping of quantum transmissions is forbidden by the no-cloning theorem and so other methods must be used to ensure high fidelity transmission of information. Quantum repeaters can resolve this problem by breaking quantum channels into shorter links. Entanglement distribution and purification at separate links could be used to ensure transmission of information over the full channel distance with the required fidelity. The objective of this WP is to improve the integration status of fibre-based quantum repeaters by creating a ‘real-world’ quantum relay – the basic state of a quantum repeater.
Figure: The experimental set-up used for a recent “real-world” quantum teleportation experiment in Geneva Switzerland. Several important aspects for real world quantum repeaters were studied using the local telecommunication network [1].
The basic idea behind a quantum relay is as follows [7]. Suppose that a qubit is to be sent from Alice to Bob. If this is done directly, for a given fidelity the transmission distance will be limited by decoherence over the quantum channel. If the flying qubit is instead sent to an intermediary: Charlie, who shares Einstein-Podolsky-Rosen (EPR) pairs of photons with Bob, the effective transmission distance can be reduced by use of quantum teleportation. To perform the teleportation, Charlie makes a joint measurement, called a Bell state measurement (BSM) between Alice’s photon and one-half of the EPR pair, which projects Bob’s photon into the state of Alice’s photon. A successful BSM implies, in particular, that a photon has left the EPR source towards Bob. This means that although the logical qubit travels the full distance from Alice to Bob, the effective distance covered by the photon to be detected by Bob is reduced and the fidelity improved.
Other QAP Activities
Researchers at the University of Geneva are also involved in other QAP work-packages:
- Rare-Earth-Ion Doped Solids with ULUND
- Comparison (Quantum Memories and Interfaces)
- Quantum Channels with UG
- Advanced sources of entangled photon pairs with CNRSGRE
- Protocols for Quantum Commerce with the CWI
- Toolbox for quantum multi-user protocols with ICFO
- Architectures with UMK
- Testing quantum systems with IPSAS
List of Publications
QAP
[1] O. Landry, J. A. W. van Houwelingen, A. Beveratos et al, Quantum teleportation over the Swisscom telecommunication network, accepted for publication in J. Optical Society of America B, Feature issue "Optical Quantum-Information Science", February 2007 quant-ph/0605010
[2] J. A. W. van Houwelingen, A. Beveratos, N. Brunner et al, Experimental quantum teleportation with a three-Bell-state analyzer, Phys. Rev. A 74 022303 (2006) quant-ph/0604211
[3] S. R. Hastings-Simon, M. U. Staudt, M. Afzelius et al, Controlled Stark shifts in Er3+-doped crystalline and amorphous waveguides for quantum state storage, Opt. Comm. 266 716 (2006) quant-ph/0603194
[4] S. A. Moiseev, C. Simon, N. Gisin, Photon Echo Quantum Memory for Arbitrary Non-Stationary Light Fields (2006) quant-ph/0609173
[5] M. U. Staudt, S. R. Hastings-Simon, M. Afzelius et al, Investigations of Optical Coherence Properties in an Erbium-doped Silicate Fiber for Quantum State Storage, Opt. Comm. 266 720 (2006) quant-ph/0603192
N. Gisin and R. Thew, Quantum communication, Nature Photonics 1 165 (2007) quant-ph/0703255
M. Halder, A. Beveratos, N. Gisin, V. Scarani, C. Simon and H. Zbinden, Entangling Independent Photons by Time Measurement (2007) quant-ph/07040758
S. A. Moiseev, C. Simon, Nicolas Gisin, Photon Echo Quantum Memory for Arbitrary Non-Stationary Light Fields (2006) quant-ph/0609173
M. U. Staudt, S. R. Hastings-Simon, M. Nilsson, M. Afzelius, V. Scarani, R. Ricken, H. Suche, W. Sohler, W. Tittel and N. Gisin, Fidelity of an optical memory based on stimulated photon echoes (2006) quant-ph/0609201
C. Simon, H. de Riedmatten, M. Afzelius et al, Quantum Repeaters with Photon Pair Sources and Multi-Mode Memories, Phys. Rev. Lett. 98 190503 (2007) quant-ph/0701239
N. Sangouard, C. Simon, M. Afzelius, and N. Gisin, Analysis of a quantum memory for photons based on controlled reversible inhomogeneous broadening, Phys. Rev. A 75 032327 (2007) quant-ph/0611165
M. Afzelius, M. U. Staudt, H. de. Riedmatten et al., Interference of Spontaneous Emission of Light from Two Atomic Ensembles, accepted for publication in N. J. Phys. arXiv:0709.1335v1
N. Brunner, N. Gisin, V. Scarani et al., Detection Loophole in Asymmetric Bell Experiments, Phys. Rev. Lett. 98 220403 (2007) quant-ph/0702130
C. Branciard, A. Ling, N. Gisin et al., Experimental Falsification of Leggett's Non-Local Variable Model, submitted to tbc arXiv:0708.0584v1
N. Gisin, Bell inequalities: many questions, a few answers, submitted to tba arXiv:0702021v2
N. Gisin, S. A. Moiseev and C. Simon, Storage and retrieval of time-bin qubits with photon-echo-based quantum memories, Phys. Rev. A 76 014302 (2007) quant-ph/0609173
M. Halder, A. Beveratos, R. T. Thew et al, High coherence photon pair source for quantum communication (2007) quant-ph/0710.1143
F. Dupuis, N. Gisin and A. A. Methot, No nonlocal box with uniform outputs is universal, submitted to tba arXiv:0609166
V. Scarani, N. Gisin, N. Brunner et al., Secrecy extraction from no-signaling correlations, Phys. Rev. A 74 042339 (2006)
N. Sangouard, C. Simon, M. Afzelius et al., Analysis of a quantum memory for photons based on controlled reversible inhomogeneous broadening, Phys. Rev. A (2007)
N. Sangouard, C. Simon, J. Minar et al., Long-Distance Entanglement Distribution with Single-Photon Sources, accepted for publication in Phys. Rev. A quant-ph/0706.1924v1
M. Afzelius, C. Simon, H. de Riedmatten et al, Multi-Mode Quantum Memory based on Atomic Frequency Combs (2008) arXiv:0805.4164
S. R. Hastings-Simon, B. Lauritzen, M. U. Staudt, et al., Controlled Stark shifts in Er3+-doped crystalline and amorphous waveguides for quantum state storage, accepted for publication in J. Opt. B quant-ph/0603194v2
J. Minar, H. de Riedmatten, C. Simon et al, Phase-noise measurements in long-fiber interferometers for quantum-repeater applications, Phys. Rev. A 77 052325 (2008) arXiv:0712.0740
Related Work
[6] B. Kraus, W. Tittel, N. Gisin, M. Nilsson, S. Kröll, and J. I. Cirac, Quantum memory for non-stationary light fields based on controlled reversible inhomogeneous broadening, Phys. Rev. A, Vol. 73, 020302(R) (2006)
[7] Long Distance Quantum Teleportation in a Quantum Relay Configuration, H. de Riedmatten, I. Marcikic, W. Tittel, H. Zbinden, D. Collins, and N. Gisin, Phys. Rev. Lett. 92, 047904 (2004)
P. Eraerds, M. Legre , A. Rochas et al., SiPM for fast Photon-Counting and Multiphoton counting, Opt. Expr. 15 14539 (2007) arXiv:0707.2325
M. U. Staudt, M. Afzelius, H. de Riedmatten, et al, Interference of Multimode Photon Echoes Generated in Spatially Separated Solid-State Atomic Ensembles, Phys. Rev. Lett. 99 173602 (2007) arXiv:0707.1814