Quantum key distribution (QKD) has been studied as an ultimate method for secure communications, and it now is emerging as a technology that can be deployed in real fibre networks. Here, we present our QKD experiments based on the differential phase shift QKD (DPS-QKD) protocol. A DPS-QKD system has a simple configuration that is easy to implement with… (More)
We report the first quantum key distribution (QKD) experiment over a 72 dB channel loss using superconducting nanowire single-photon detectors (SSPD, SNSPD) with the dark count rate (DCR) of 0.01 cps. The DCR of the SSPD, which is dominated by the blackbody radiation at room temperature, is blocked by introducing cold optical bandpass filter. We employ the… (More)
We report on the quantum key distribution experiment using ultra-low-noise 2-GHz sinusoidally gated InGaAs/InP avalanche photodiodes. The detectors enabled us to distribute secure keys over 100 km with a bit rate of 24 kbps.
MapReduce is widely used for BigData processing. It was originally designed to overcome the I/O bottleneck of commodity servers. However, several high speed storage and network devices have recently emerged, and speeds continue to increase. Employing such brand new devices will solve the I/O bottleneck, making the CPU the next serious bottleneck in the… (More)
The analysis and optimization of complex systems can be reduced to mathematical problems collectively known as combinatorial optimization. Many such problems can be mapped onto ground-state search problems of the Ising model, and various artificial spin systems are now emerging as promising approaches. However, physical Ising machines have suffered from… (More)
A novel secure communication network with quantum key distribution in a metropolitan area is reported. Different QKD schemes are integrated to demonstrate secure TV conferencing over a distance 45 km, stable long-term operation, and application to secure mobile phones.