Continuous-variable quantum passive optical network
arxiv(2024)
摘要
Building scalable and secure quantum networks with many users has a high
application potential but also holds many practical challenges. A significant
stride in this pursuit involves extending quantum key distribution, an
information-theoretically secure method for establishing cryptographic keys
between two distant users, from a point-to-point protocol implemented on direct
optical connections to a quantum access network. Yet, realizations of quantum
access networks have, so far, relied on probabilistic or time-sharing
strategies. Here, we show theoretically and experimentally that a solution
without these constraints can come from the exclusive features of
continuous-variable systems. Based on coherent states, we propose
continuous-variable quantum passive-optical-network (CV-QPON) protocols,
enabling deterministic and simultaneous secret key generation among all network
users. We achieve this by leveraging the inherent wave-like property of
coherent states split at a beam splitter and electric-field quadrature
measurements. We show two protocols with different trust levels assigned to the
network users and experimentally demonstrate key generation in a quantum access
network with 8 users, each with an 11 km span of access link. Depending on the
trust assumptions about users, we reach 1.5 Mbits/s and 2.1 Mbits/s of total
network key generation. Demonstrating the potential to expand the network's
capacity to accommodate tens of users at a high rate, our CV-QPON protocols
offer a pathway toward establishing low-cost, high-rate, and scalable quantum
access networks using standard telecom technologies and directly exploiting the
existing access network infrastructure.
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