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.
Highlights
Quantum key distribution (QKD), which enables the generation of secure shared randomness between two distant parties (Alice and Bob) [1], is the most advanced quantum technology to date [2,3,4]
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
We have developed a new protocol, SR-CV-QKD, that eliminates the need to transmit a local oscillator (LO)
Summary
Quantum key distribution (QKD), which enables the generation of secure shared randomness between two distant parties (Alice and Bob) [1], is the most advanced quantum technology to date [2,3,4]. We achieve this by noticing that a common reference frame between Alice and Bob can be established by a method that, instead of transmitting the LO, uses regularly spaced reference pulses whose quadratures are measured by Bob to estimate Alice’s phase reference This new protocol, which we call self-referenced CV-QKD (SR-CV-QKD), greatly simplifies the hardware requirements at Alice’s and Bob’s stations since it enables them both to employ independent (truly local) LOs. In addition, SR-CV-QKD obviates a key assumption of most CV-QKD security proofs [14]—namely, that the LO is trusted—and provides a more secure implementation of CV-QKD.
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