Rate-distance tradeoff and resource costs for all-optical quantum repeaters

Abstract

We present a resource-performance tradeoff of an all-optical quantum repeater that uses photon sources, linear optics, photon detectors and classical feedforward at each repeater node, but no quantum memories. We show that the quantum-secure key rate has the form R(η) = Dη s bits per mode, where η is the end-to-end channel's transmissivity, and the constants D and s are functions of various device inefficiencies and the resource constraint, such as the number of available photon sources at each repeater node. Even with lossy devices, we show that it is possible to attain s < 1, and in turn outperform the maximum key rate attainable without quantum repeaters, R direct (η) = − log 2 (1 − η) ≈ (1/ ln 2)η bits per mode for η 1, beyond a certain total range L, where η ∼ e −αL in optical fiber. We also propose a suite of modifications to a recently-proposed alloptical repeater protocol that ours builds upon, which lower the number of photon sources required to create photonic clusters at the repeaters so as to outperform R direct (η), from ∼ 10 11 to ∼ 10 6 photon sources per repeater node. We show that the optimum separation between repeater nodes is independent of the total range L, and is around 1.5 km for assumptions we make on various device losses.

Large-scale quantum photonic circuits in silicon

“…Recent studies on resource requirements of scalable linear optics quantum computing [27] and all-optical quantum repeaters [108] suggest that these systems will require a large number of photonic elements. While new protocols for the efficient generation of cluster states based on percolation theory [18,109,110] may reduce these resource requirements and the number of feed-forward elements, large unitary transformations on many optical modes will still be necessary.…”

“…Compact, low loss, and gigahertz-rate modulators remain an elusive building block for linear optics quantum computing; they are at the center of proposals for realizing error tolerant quantum photonic circuits [27,108]. In silicon, lossless modulation at high speed is particularly challenging, since high-speed modulation is achieved using the inherently lossy plasma dispersion effect [62].…”

Components of Long-Distance Quantum Communication. Part 2

“…Если в качестве носителей информации исполь-зовать примесные криста ллы, активиро-ванные редкоземельными ионами, то в бли-жайшей перспективе устройства квантовой памяти смогут записывать и воспроизводить оптические импульсы, спектральная ширина которых не превышает нескольких гигагерц. Если же рассматривать полностью оптический протокол квантового повторителя (без кванто-вой памяти) [66], то его реализация потребует создания многофотонных перепутанных кван-товых состояний с помощью огромного числа (миллиона) однофотонных источников [67].…”

“…Идея такого услов-ного приготовления однофотонных состояний была предложена Д. Н. Клышко в 1977 году [79], а первый эксперимент был поставлен Хонгом и Манделем в 1986 году [80]. means of huge number (of the order of one million) of single-photon sources [67].…”

Finite-size analysis of measurement-device-independent quantum cryptography with continuous variables

“…[7] sets the fundamental limit of point-to-point QKD and, as such, it marks the edge when private communication inevitably needs quantum repeaters. This benchmark has already had a wide application in recent works [16][17][18][19][20][21][22][23][24][25][26][27][28][29].…”