One-Way Quantum Key Distribution System Based on Planar Lightwave Circuits

Abstract

We developed a one-way quantum key distribution (QKD) system based upon a planar lightwave circuit (PLC) interferometer. This interferometer is expected to be free from the backscattering inherent in commercially available two-way QKD systems and phase drift without active compensation. A key distribution experiment with spools of standard telecom fiber showed that the bit error rate was as low as 6% for a 100-km key distribution using an attenuated laser pulse with a mean photon number of 0.1 and was determined solely by the detector noise. This clearly demonstrates the advantages of our PLC-based one-way QKD system over two-way QKD systems for long distance key distribution.

Quantum encoder and decoder for practical quantum key distribution using a planar lightwave circuit

“…These results suggest that our PLC-based interferometer allows us to implement a QKD system insensitive to polarization effects that may occur in the transmission fiber, since the same balancing condition is sufficient to achieve polarization insensitivity [38]. The polarization-insensitive operation of a time-division interferometer based on our PLC AMZI has actually been proven by the authors using the experimental setup shown in Figure 7 [35,36]. Two PLC AMZIs and a polarization scrambler were connected in series using a single-mode fiber patch cable, and relatively intense optical pulses were introduced into the first AMZI.…”

“…The key to our proposal is the use of planar lightwave circuit (PLC) technology [32][33][34][35][36], which enables us to implement a reliable interferometric optical system that is robust to change in ambient conditions [37]. By using PLC technology, we developed compact and easy-to-use passive interferometric devices to manipulate a photonic time-bin qubit with increased stability, reliability, and flexibility.…”

“…unit) 10 15 1959 This clearly shows that our PLC-based interferometer is sufficient to implement a polarization-insensitive QKD system. The most promising features of the PLC-based interferometer are that it is robust to change in ambient conditions and it has been proven [36]. Figure 9 shows the long-term stability of our PLC-based interferometer.…”

Active phase compensation of quantum key distribution system

“…Interferometers made of low thermal factor materials [13] or integrated planar silica waveguide with thermal and mechanical isolation can be used in passive compensation [14,15] . Another improved way to passively compensate for phase drift is to find the environment temperature of interferometers, at which the difference between the modal phase shifts in the long and short arms of the AMZI (ș L ș S ) is multiples of 2ʌ [16] . Although these measures can suppress the harmful temperature disturbance of environment, there must be accurate temperature controller with precision of 0.01 in the system.…”

System Design for a Long-Line Quantum Repeater

“…An experimental metropolitan-area QKD network has been developed and deployed in the Boston area [18], and similar efforts are underway in Japan [19] and Europe [20]. Efforts to extend these networks to wider areas are constrained by loss in the communication channel, which results in exponential decay in throughput as distance increases.…”