Finite-size security of continuous-variable quantum key distribution with digital signal processing

Area of Science:

• Quantum Information Science
• Quantum Cryptography
• Optical Communication

Background:

• Continuous-variable quantum key distribution (CV-QKD) presents implementation advantages over discrete-variable (DV) QKD, including lower cost and compatibility with wavelength division multiplexing.
• The continuous nature of CV-QKD poses challenges for practical signal processing and has hindered complete security proofs.
• Existing CV-QKD protocols often lack rigorous security guarantees in finite-key regimes against sophisticated attacks.

Purpose of the Study:

• To develop a robust method for estimating the fidelity of optical pulses to coherent states using heterodyne measurements.
• To construct a secure binary phase-modulated CV-QKD protocol.
• To provide a complete security proof for the proposed CV-QKD protocol in the finite-key-size regime against general coherent attacks.

Main Methods:

• Proposal of a novel, tight, and robust method for fidelity estimation of optical pulses via heterodyne measurements.
• Construction of a binary phase-modulated CV-QKD protocol.
• Application of DV QKD proof techniques to establish security in the finite-key-size regime.

Main Results:

• A reliable method for fidelity estimation in CV-QKD systems is presented.
• A binary phase-modulated CV-QKD protocol with proven security is developed.
• The security of the protocol is demonstrated against general coherent attacks within the finite-key-size framework.

Conclusions:

• The developed fidelity estimation method enhances the practicality of CV-QKD.
• The proposed CV-QKD protocol achieves complete security, addressing a critical gap in the field.
• This work paves the way for the secure and widespread adoption of CV-QKD, leveraging its inherent advantages.