Self-referenced continuous-variable quantum key distribution protocol

TL;DR

This paper presents a novel self-referenced continuous-variable quantum key distribution protocol that removes the need for transmitting a high-power local oscillator, simplifying hardware and enabling scalable quantum communication networks.

Contribution

It introduces a new CV-QKD protocol using reference pulses for phase alignment, demonstrated experimentally, and analyzes its secret key rate considering quantum uncertainties.

Findings

Successful fiber-based experimental demonstration

Quantified secret key rates with experimental parameters

Protocol simplifies hardware for scalable CV-QKD implementations

Abstract

We introduce a new continuous-variable quantum key distribution (CV-QKD) protocol, self-referenced CV-QKD, that eliminates the need for transmission of a high-power local oscillator between the communicating parties. In this protocol, each signal pulse is accompanied by a reference pulse (or a pair of twin reference pulses), used to align Alice's and Bob's measurement bases. The method of phase estimation and compensation based on the reference pulse measurement can be viewed as a quantum analog of intradyne detection used in classical coherent communication, which extracts the phase information from the modulated signal. We present a proof-of-principle, fiber-based experimental demonstration of the protocol and quantify the expected secret key rates by expressing them in terms of experimental parameters. Our analysis of the secret key rate fully takes into account the inherent uncertainty associated with the quantum nature of the reference pulse(s) and quantifies the limit at which the theoretical key rate approaches that of the respective conventional protocol that requires local oscillator transmission. The self-referenced protocol greatly simplifies the hardware required for CV-QKD, especially for potential integrated photonics implementations of transmitters and receivers, with minimum sacrifice of performance. As such, it provides a pathway towards scalable integrated CV-QKD transceivers, a vital step towards large-scale QKD networks.