Polarization and quantum differential phase

Nilesh Sharma, Chandrashekar Radhakrishnan, Anil Prabhakar

The effect of polarization mismatched coherent pulses on the key rates of differential phase based MDI QKD is investigated. It is found that this protocol can withstand a polarization mismatch of at most 11°.

Alfredo Luis

Yuki Iwai, Toshimori Honjo, Kyo Inoue +4 more

We propose and demonstrate a polarization-independent, differential-phase-shift, quantum-key distribution system with upconversion detectors. Even though the detectors have polarization dependency, use of alternative polarization modulation and a two-bit delay interferometer achieves polarization-insensitive operation. In an experiment, sifted key bits were polarization-independently generated over 50 km fiber.

Chien Chou, Hui-Kang Teng, Chien-Chung Tsai +1 more

A differential-phase decoder (DPD) together with a polarization common-path optical heterodyne interferometer is set up. Based on this interferometric configuration and a novel balanced-detector scheme, the performance of the quantum-noise-limited differential-phase decoder is demonstrated and analyzed. The minimum-detectable differential phase is on the order of 10(-7) rad/sqrt Hz when a 2.5 mW He-Ne laser is used. Verified experimentally, the DPD is immune to the common-phase noise induced by an electro-optic phase modulator or by thermal disturbance within the interferometer. This signifies that the minimum-detectable differential phase can become 10(-8) rad/sqrt Hz if a 300 mW continuous wave laser is employed instead.

Stephen Mark Barnett, David Thomas Pegg