Provably secure and practical quantum key distribution over 307 km of optical fibre

Korzh, Boris; Lim, Charles Ci Wen; Houlmann, Raphaël; Gisin, Nicolas; Li, Mingjun; Nolan, Daniel A.; Sanguinetti, Bruno; Thew, Rob; Zbinden, Hugo

doi:10.1038/nphoton.2014.327

Cited by 475 publications

(393 citation statements)

References 33 publications

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“…Using two of such states, see figure 1(b), plus post-selection succeeding with a probability proportional to p c , one can then end up with an entangled state between two ensembles A 1 and A 2 , and their corresponding photonic modes P 1 2 , provided that p c , the excitation probability, is much lower than one. The setup in figure 1(b) was investigated in [15] and it turned out that primarily the ñ ñ ñ ñ | | | | 1 1 1 1 P A P A Figure 1.…”

Section: Introductionmentioning

confidence: 99%

Memory-assisted quantum key distribution resilient against multiple-excitation effects

Piparo

Sinclair

Razavi

2017

Quantum Sci. Technol.

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Memory-assisted measurement-device-independent quantum key distribution (MA-MDI-QKD) has recently been proposed as a technique to improve the rate-versus-distance behavior of QKD systems by using existing, or nearly-achievable, quantum technologies. The promise is that MA-MDI-QKD would require less demanding quantum memories than the ones needed for probabilistic quantum repeaters. Nevertheless, early investigations suggest that, in order to beat the conventional memoryless QKD schemes, the quantum memories used in the MA-MDI-QKD protocols must have high bandwidth-storage products and short interaction times. Among different types of quantum memories, ensemble-based memories offer some of the required specifications, but they typically suffer from multiple excitation effects. To avoid the latter issue, in this paper, we propose two new variants of MA-MDI-QKD both relying on single-photon sources for entangling purposes. One is based on known techniques for entanglement distribution in quantum repeaters. This scheme turns out to offer no advantage even if one uses ideal single-photon sources. By finding the root cause of the problem, we then propose another setup, which can outperform single memory-less setups even if we allow for some imperfections in our single-photon sources. For such a scheme, we compare the key rate for different types of ensemble-based memories and show that certain classes of atomic ensembles can improve the rate-versus-distance behavior.

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Section: Introductionmentioning

confidence: 99%

Memory-assisted quantum key distribution resilient against multiple-excitation effects

Piparo

Sinclair

Razavi

2017

Quantum Sci. Technol.

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“…One of the key features of the practical QC systems is the signal transmitted through a separate channel which synchronizes its transmitter and receiver modules. For errorless operation of the system, compensation mechanisms against negative effects of signal distortion should be considered [4,5].…”

Section: Introductionmentioning

confidence: 99%

Synchronization signal distortion in quantum communication systems

Dubrovskaia¹,

Chivilikhin²

2017

Nanosystems: Phys. Chem. Math.

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An important problem in the practical implementation of fiber optical quantum communication systems is to synchronize the sender and receiver modules using a separate optical channel. The signal visibility in the quantum channel, which contributes to quantum bit error rate, is influenced by the synchronization signal delay. In this work, we investigate the dependence of the synchronization signal parameters on the dispersive effects in the fiber for a subcarrier wave quantum communication system (SCWQC), which is promising for quantum networking applications. The ITU-T G.652D standard single mode optical fiber was used for modeling. The maximum calculated phase mismatch of the synchronization signal for the system operating at 100 km fiber length corresponds to 1.7 ps signal time delay. The results show that dispersion causes significant signal distortion, therefore additional phase adjustment at least every 2.3 hours is required for stable system operation.

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“…Additionally, multiphoton coherent states can be produced with high repetition rates and they have high transmission rates in the channels connecting the quantum nodes. For example, in long distance quantum key distribution scenarios coherent states with both low [16] and high mean pho- * Electronic address: Zsolt.Bernad@physik.tu-darmstadt.de ton numbers [17] have already been successfully applied. Recently, an entanglement purification scheme has been proposed in the context of the hybrid quantum repeater using chains of atoms, optical cavities and far-off resonant matter-field interactions [18].…”

Section: Introductionmentioning

confidence: 99%

Multiphoton-state-assisted entanglement purification of material qubits

et al. 2016

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We propose an entanglement purification scheme based on material qubits and ancillary coherent multiphoton states. We consider a typical QED scenario where material qubits implemented by two-level atoms fly sequentially through a cavity and interact resonantly with a single-mode of the radiation field. We explore the theoretical possibilities of realizing a high-fidelity two-qubit quantum operation necessary for the purification protocol with the help of a postselective balanced homodyne photodetection. We demonstrate that the obtained probabilistic quantum operation can be used as a bilateral operation in the proposed purification scheme. It is shown that the probabilistic nature of this quantum operation is counterbalanced in the last step of the scheme where qubits are not discarded after inadequate qubit measurements. As this protocol requires present-day experimental setups and generates high fidelity entangled pairs with high repetition rates, it may offer interesting perspectives for applications in quantum information theory.

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Provably secure and practical quantum key distribution over 307 km of optical fibre

Cited by 475 publications

References 33 publications

Memory-assisted quantum key distribution resilient against multiple-excitation effects

Memory-assisted quantum key distribution resilient against multiple-excitation effects

Synchronization signal distortion in quantum communication systems

Multiphoton-state-assisted entanglement purification of material qubits

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