The Error Tolerance Bound for Secure Multi-Qubit QKD Against Incoherent Attack

Abstract

The tolerance bound for quantum symbol error rate in a multi-qubit quantum key distribution system is derived in consideration of an incoherent attack on a single-photon quantum channel, where multi-qubit encoding and measurement can be applied to a single photon in combination of polarization, phase, and frequency modulations. This paper presents a solid theoretical evidence of a multiqubit gain in secrecy performance.