Practical Quantum Key Distribution with Non-Phase-Randomized Coherent States

Abstract

Quantum key distribution (QKD) based on coherent states is well known for its implementation simplicity, but it suffers from loss-dependent attacks based on optimal unambiguous state discrimination. Crucially, previous research has suggested that coherent-state QKD is limited to short distances, typically below 100 km assuming standard optical fiber loss and system parameters. In this work, we propose a six-coherent-state phase-encoding QKD protocol that is able to tolerate the total loss of up to 38 dB assuming realistic system parameters, and up to 56 dB loss assuming zero noise. The security of the protocol is calculated using a recently developed security proof technique based on semi-definite programming, which assumes only the inner-product information of the encoded coherent states, the expected statistics, and that the measurement is basis-independent. Our results thus suggest that coherent-state QKD could be a promising candidate for high-speed provably-secure QKD.

Binary Communication with Gazeau–Klauder Coherent States

“…As coherent states with a non-randomized phase have recently attracted new attention [5] we believe that our analysis, despite its simplicity, can serve as a modest theoretical contribution for further practical developments utilizing Gazeau-Klauder coherent states in quantum communication and information processing and in a context of hybrid protocols [24].…”

“…It was quite early when the Quantum Community recognized the usefulness of the 'most classical' among quantum states-the coherent states-in quantum information processing [1][2][3][4]. Even recently coherent states with a non-random phase, despite certain limitations [2], have found their application in the very hot branch of quantum communication related to quantum key distribution [5]. The idea is simply to utilize as an alphabet a pair of coherent states [1]…”

Optimizing Decoy‐State Protocols for Practical Quantum Key Distribution Systems

“…Therefore, the phase randomization is an extra burden in such implements. Recently, the security analysis without phase randomization is proposed [ 63 ] that appears to solve the problem. Moreover, the intensity fluctuations of the source are also analyzed.…”

Currents in a Quantum Nanoring Controlled by Non-Classical Electromagnetic Field

“…The second class of states consists of coherent states forming pairs of the celebrated Schrödinger cats: where denotes a coherent state and is a normalization factor. It is hard to overestimate a role played by coherent states in quantum information processing [ 31 , 32 , 33 , 34 , 35 ] and, in particular, the states in Equation ( 10 ), as orthogonal and well distinguishable, are natural candidates for logical qubits. Further we show that currents in nanorings can serve as an auxiliary quantifier for their detection.…”

“…Properties of persistent currents in a presence of a non-classical magnetic flux flowing both in superconducting and non-superconducting rings reflect many non-classical properties of magnetic flux treading the sample and modifying a phase of electrons. Carefully prepared non-classical electromagnetic fields applicable in quantum information processing [ 31 , 32 , 33 , 34 , 35 ] are shown to modify properties of currents flowing in nanosystems [ 20 , 36 , 37 , 38 , 39 , 40 ] (and Ref. [ 41 ] for detailed review) under external field approximation [ 36 ] assumed.…”