Parameter regimes for a single sequential quantum repeater

Abstract

Quantum key distribution allows for the generation of a secret key between distant parties connected by a quantum channel such as optical fibre or free space. Unfortunately, the rate of generation of a secret key by direct transmission is fundamentally limited by the distance. This limit can be overcome by the implementation of so-called quantum repeaters. Here, we assess the performance of a specific but very natural setup called a single sequential repeater for quantum key distribution. We offer a fine-grained assessment of the repeater by introducing a series of benchmarks. The benchmarks, which should be surpassed to claim a working repeater, are based on finite-energy considerations, thermal noise and the losses in the setup. In order to boost the performance of the studied repeaters we introduce two methods. The first one corresponds to the concept of a cut-off, which reduces the effect of decoherence during storage of a quantum state by introducing a maximum storage time. Secondly, we supplement the standard classical post-processing with an advantage distillation procedure. Using these methods, we find realistic parameters for which it is possible to achieve rates greater than each of the benchmarks, guiding the way towards implementing quantum repeaters. * These authors contributed equally; f.d.rozpedek@tudelft.nl arXiv:1705.00043v2 [quant-ph]

Efficient Computation of the Waiting Time and Fidelity in Quantum Repeater Chains

“…When the first pair in one of the segments is ready, it has to wait until the second segment finalizes, and it decoheres while waiting. In this context, one may need to discard the entanglement after some maximum amount of time [43], [47], [48]. Entanglement is also used as a resource for implementing non-local gates in distributed quantum computers [49].…”

Practical figures of merit and thresholds for entanglement distribution in quantum networks

“…(The degree of a node is defined to be the number of edges connected to that node.) Several different platforms have been considered for quantum memories in quantum repeater networks, such as trapped ions [46], Rydberg atoms [47,48], atom-cavity systems [49,50], NV centers in diamond [43,[51][52][53][54][55], individual rare-earth ions in crystals [56], and superconducting processors [57].…”

Parameter regimes for surpassing the PLOB bound with error-corrected qudit repeaters

“…They shorten the distance of direct transmissions by introducing intermediate repeater stations such that losses and errors can be tackled using entanglement heralding, quantum memories, entanglement distillation, or quantum error-correcting codes (QECCs) [20]. Recent investigations have shown that quantum repeaters based on currently available technology have the potential to surpass the PLOB-repeaterless bound, even with a single intermediate repeater station [21][22][23][24][25][26]. Laboratory experiments have been reported which prove that it is in principle possible to surpass the PLOB-repeaterless bound over distances of tens and hundreds of kilometers [27][28][29].…”