Overcoming lossy channel bounds using a single quantum repeater node

Luong, David; Jiang, Liang; Kim, J.; Lütkenhaus, Norbert

doi:10.1007/s00340-016-6373-4

Cited by 52 publications

(99 citation statements)

References 25 publications

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“…The new bound in this paper coincides with the finite-energy variant of the bound by Takeoka et al, see [21,22]. The loss parameter η ranges from 0 to´-2 10 20 , which is the range of expected losses for transmissions across fibers with length »1000 km with an attenuation length of 22 km [18].…”

Section: Resultssupporting

confidence: 82%

“…As the experimental results improve it will be necessary to evaluate whether or not an implementation has achieved a rate not possible via direct communications. This can be done by comparing the attainable rate with a quantum repeater [12][13][14][15][16][17][18][19] to the capacity of the associated quantum channel (i.e. direct transmission) for that task.…”

Section: Introductionmentioning

confidence: 99%

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Assessing the performance of quantum repeaters for all phase-insensitive Gaussian bosonic channels

2016

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One of the most sought-after goals in experimental quantum communication is the implementation of a quantum repeater. The performance of quantum repeaters can be assessed by comparing the attained rate with the quantum and private capacity of direct transmission, assisted by unlimited classical two-way communication. However, these quantities are hard to compute, motivating the search for upper bounds. Takeoka, Guha and Wilde found the squashed entanglement of a quantum channel to be an upper bound on both these capacities. In general it is still hard to find the exact value of the squashed entanglement of a quantum channel, but clever sub-optimal squashing channels allow one to upper bound this quantity, and thus also the corresponding capacities. Here, we exploit this idea to obtain bounds for any phase-insensitive Gaussian bosonic channel. This bound allows one to benchmark the implementation of quantum repeaters for a large class of channels used to model communication across fibers. In particular, our bound is applicable to the realistic scenario when there is a restriction on the mean photon number on the input. Furthermore, we show that the squashed entanglement of a channel is convex in the set of channels, and we use a connection between the squashed entanglement of a quantum channel and its entanglement assisted classical capacity. Building on this connection, we obtain the exact squashed entanglement and two-way assisted capacities of the d-dimensional erasure channel and bounds on the amplitude-damping channel and all qubit Pauli channels. In particular, our bound improves on the previous best known squashed entanglement upper bound of the depolarizing channel.

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Section: Resultssupporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Assessing the performance of quantum repeaters for all phase-insensitive Gaussian bosonic channels

2016

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“…MA-MDI-QKD, nevertheless, provides an intermediary solution compatible with the state of the art, which can pave the way for future generations of quantum networks. Note that in special cases where the total loss per unit of length is higher than that of the fiber loss, e.g., in passive optical networks with high splitting losses, MA-MDI-QKD offers rate advantages at shorter distances [42]. This could perhaps be the first realistic scenario in which quantum memories, with all their known practical limitations, can be used to offer a tangible benefit.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Measurement-device-independent quantum key distribution with nitrogen vacancy centers in diamond

2017

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Memory-assisted measurement-device-independent quantum key distribution (MA-MDI-QKD) has recently been proposed as a possible intermediate step towards the realization of quantum repeaters. Despite its relaxing some of the requirements on quantum memories, the choice of memory in relation to the layout of the setup and the protocol has a stark effect on our ability to beat existing no-memory systems. Here, we investigate the suitability of nitrogen vacancy (NV) centers, as quantum memories, in MA-MDI-QKD. We particularly show that moderate cavity enhancement is required for NV centers if we want to outperform no-memory QKD systems. Using system parameters mostly achievable by today's state of the art, we then anticipate some total key rate advantage in the distance range between 300 and 500 km for cavity-enhanced NV centers. Our analysis accounts for major sources of error including the dark current, the channel loss, and the decoherence of the quantum memories.

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“…There have been many proposals constructed in a way that signals from the parties do not have to arrive at the same time to the middle station, one possibility is to utilize quantum memory assisted protocols containing one middle node [4,25,26,28], which can also offer a square root improvement in the secret key rate capacity since independent successful arrival of the signals to middle station suffices for key generation. Also, a scheme without the need for quantum memories has been introduced in [23] offering the same square root improvement using optical switches and the idea of multiplexing.…”

Section: Introductionmentioning

confidence: 99%

“…This approach will serve as a benchmark that pushes technology towards a fully scalable multinode quantum repeater. Our approach is to extend the protocol [4] with the idea of using more quantum memories at the middle station and operating them in a parallel manner (using a multiplexing technique), which was also applied in [23,27,29]. We mention that in [27,29] this idea has been used in a multi-node repeater setting.…”

Section: Introductionmentioning

confidence: 99%

Beating direct transmission bounds for quantum key distribution with a multiple quantum memory station

Trényi

Lütkenhaus

2020

Phys. Rev. A

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Overcoming repeaterless bounds for the secret key rate capacity of quantum key distribution protocols is still a challenge with current technology. D. Luong et al. [Applied Physics B 122, 96 (2016)] proposed a protocol to beat a repeaterless bound using one pair of quantum memories. However, the required experimental parameters for the memories are quite demanding. We extend the protocol with multiple pairs of memories, operated in a parallel manner to relax these conditions. We quantify the amount of relaxation in terms of the most crucial memory parameters, given the number of applied memory pairs. In the case of high-loss channels we found that adding only a few pair of memories can make the crossover possible.

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Overcoming lossy channel bounds using a single quantum repeater node

Cited by 52 publications

References 25 publications

Assessing the performance of quantum repeaters for all phase-insensitive Gaussian bosonic channels

Assessing the performance of quantum repeaters for all phase-insensitive Gaussian bosonic channels

Measurement-device-independent quantum key distribution with nitrogen vacancy centers in diamond

Beating direct transmission bounds for quantum key distribution with a multiple quantum memory station

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