Repeaterless quantum key distribution with efficient finite-key analysis overcoming the rate-distance limit

Area of Science:

• Quantum Information Science
• Cryptography
• Quantum Optics

Background:

• Point-to-point quantum key distribution (QKD) is limited by linear scaling.
• Twin-field (TF) QKD was proposed to exceed this bound using a central station.
• Previous security proofs for TF-QKD were limited to the infinite key scenario.

Purpose of the Study:

• To propose a variant of TF-QKD with reduced monitoring costs.
• To provide an information-theoretic security proof for finite communication times.
• To demonstrate that the proposed protocol can overcome the linear scaling bound.

Main Methods:

• Development of a cost-effective monitoring methodology for TF-QKD.
• Formulation of an information-theoretic security proof for finite key generation.
• Simulation of the key rate to evaluate protocol performance.

Main Results:

• The proposed TF-QKD variant achieves a key rate exceeding the linear bound.
• The protocol demonstrates this capability within a practical timeframe (10^12 pulses).
• The security proof is applicable to finite communication durations, addressing previous limitations.

Conclusions:

• The conjecture that TF-QKD can beat the repeaterless bound is positively solved.
• This work provides a practical and secure QKD protocol for realistic communication scenarios.
• The findings pave the way for enhanced secure communication systems leveraging quantum mechanics.