Macroscopic Differential Phase Shift Quantum Key Distribution Using an Optically Pre-Amplified Receiver

Abstract

Since it was noted that quantum computers could break public key cryptosystems based on number theory, extensive studies have been undertaken on quantum cryptography, which offers unconditionally secure communication based on quantum mechanics. We investigate a quantum key distribution (QKD) scheme using macroscopic coherent light with optically pre-amplified direct differential detection. A transmitter “Alice” sends a series of two macroscopic nonorthogonal coherent states that partially overlap due to quantum noise. A receiver “Bob” amplifies and receives it with direct differential detection followed by a thresholding process. To avoid difficulties in detection, our scheme uses conventional direct differential photodetection, not single-photon detection or homodyne detection as in previous QKD protocols. System performance assuming some eavesdropping is evaluated, the results of which suggest that our scheme is usable for short or medium distance.

Effects of atmospheric turbulence and misalignment-induced fading on the secrecy performance of IM/DD free-space CV-QKD systems using a Gaussian beam

“…Nevertheless, the use of heterodyne/homodyne receivers requires a sophisticated phase-stabilized local light, which results in a higher implementation cost. To avoid such issue, differential-phase-shift-keying (DPSK)based CV-QKD using a delay interferometer was developed 3 . To further simplify CV-QKD configurations, intensity modulation/direct detection (IM/DD) CV-QKD systems have been recently proposed for implementation over both *pvtrinh@nict.go.jp; phone +81-42-327-5982; fax +81-42-327-6825; www.nict.go.jp optical fiber 4,5 and free-space optics (FSO) 6,7,8 .…”

Intensity modulation and direct detection quantum key distribution based on quantum noise

“…However, homodyne detection requires phase-stabilized local light, which is not easy to implement. Based on the above background, we previously proposed differential-phase-shift-keying (DPSK)-based CVQKD [5,6]. A phase-modulated coherent pulse train with moderate power is transmitted, and it is detected using a delay Mach-Zehnder interferometer.…”