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Rate-distance tradeoff and resource costs for all-optical quantum repeaters | Mihir Pant
; Hari Krovi
; Dirk Englund
; Saikat Guha
; | Date: |
4 Mar 2016 | Abstract: | We present a resource-performance tradeoff calculation of an all-optical
repeater architecture that uses photon sources, linear optics, photon detectors
and classical feedforward at each repeater node, but no quantum memories. The
secret-key generation rate attainable by any repeaterless quantum key
distribution protocol over an optical channel of transmissivity $eta$ is at
most $R_{
m direct}(eta) = -log_2(1-eta) approx (1/ln 2)eta$ bits per
mode, for $eta ll 1$. With the device resources (number of photon sources and
detectors) held fixed at each repeater node, we show that the key rate achieved
by our protocol has the form $R(eta) = Deta^s$ bits per mode, where $D$ and
$s$ are functions of the aforesaid resource constraint and various losses in
the system. Even with lossy sources, inefficient detectors, and coupling and
propagation losses in optical fibers and waveguides, we show that it is
possible to achieve $s < 1$, and hence outperform the repeaterless rate-loss
upper bound $R_{
m direct}(eta)$ beyond a certain total range $L$, where
$eta sim e^{-alpha L}$ in optical fiber. We also propose a suite of
modifications to a recently-proposed all-optical repeater protocol that our
protocol builds upon, which lowers the number of photon sources required to
create photonic clusters at the repeater nodes so as to outperform the
repeaterless bound, by $5$ orders of magnitude, from $sim 10^{11}$ to $sim
10^{6}$ photon sources per repeater node. We show that the optimum separation
between repeater stations is independent of the total range $L$, and is around
$1.5$ km for assumptions we make on various device losses. | Source: | arXiv, 1603.1353 | Services: | Forum | Review | PDF | Favorites |
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