Quantum key distribution with dual detectors

Abstract

To improve the performance of a quantum-key-distribution (QKD) system, high speed, low dark count single photon detectors (or low-noise homodyne detectors) are required. However, in practice, a fast detector is usually noisy. Here, we propose a dual-detector method to improve the performance of a practical QKD system with realistic detectors: the legitimate receiver randomly uses either a fast (but noisy) detector or a quiet (but slow) detector to measure the incoming quantum signals. The measurement results from the quiet detector can be used to bound the eavesdropper's information, while the measurement results from the fast detector are used to generate a secure key. We apply this idea to various QKD protocols. Simulation results demonstrate significant improvements of the secure key rate in the lower loss regime in both Bennett-Brassard 1984 (BB84) protocol with ideal single photon source and Gaussian-modulated coherent states protocol; while for decoy-state BB84 protocol with weak coherent source, the improvement is moderate. We also discuss various practical issues in implementing the dual-detector scheme. © 2007 The American Physical Society.