Fast and simple one-way quantum key distribution

Abstract

We present and demonstrate a new protocol for practical quantum cryptography, tailored for an implementation with weak coherent pulses to obtain a high key generation rate. The key is obtained by a simple time-of-arrival measurement on the dataline; the presence of an eavesdropper is checked by an interferometer on an additional monitoring line. The setup is experimentally simple; moreover, it is tolerant to reduced interference visibility and to photon number splitting attacks, thus featuring a high efficiency in terms of distilled secret bit per qubit.

Free-running InGaAs single photon detector with 1 dark count per second at 10% efficiency

“…The system is clocked at 625 MHz and incorporates all of the necessary components for full quantum key distribution, including real-time post-processing for error correction, privacy amplification and authentication. 18 The implementation is based on the coherent-one way protocol 19 which uses two detectors, one for measuring the bit value encoded in the photon arrival time (data detector) and a second one to measure the visibility of the coherent state interference (monitor detector), which guarantees security. Due to their extremely low dark count rates, the detectors presented in this Letter are especially suited for utilization in QKD scenarios with very long fiber lengths.…”

The SECOQC quantum key distribution network in Vienna

“…The COW QKD system was developed by GAP [7]- [10]. A schematic of the configuration is drawn in figure 10.…”

Analysis of coherent quantum cryptography protocol vulnerability to an active beam-splitting attack

“…This protocol is easy to implement in experiment, and it has been used in the project on the design of European network for quantum key distribution SEC-OQC [21]. However, despite prevalence of this method and its high practical importance, an analysis of the possibility of attacks, which give to an eavesdropper an opportunity to obtain information about a quantum key, is an important task [18][19][20][21][22][23][24][25][26]. We note that lower bounds on the key generation rate of a variant of the coherentone-way quantum key distribution protocol have been obtained in Ref.…”

“…These protocols are inspired by classical communications with optical fiber systems [20]. The most significant advantage of the COW protocol is simplicity of its realization [13,[18][19][20], which is related to its simple optical scheme. This protocol is easy to implement in experiment, and it has been used in the project on the design of European network for quantum key distribution SEC-OQC [21].…”

“…Nevertheless, the way to their implementation encounters with a number of technological challenges. One of the most promising methods of operating with quantum systems used in commercial devices consists of using coherent states of light for quantum key distributions (such as coherent one-way protocol, COW) [18][19][20]. These protocols are inspired by classical communications with optical fiber systems [20].…”