Long-Term Stable Polarized Adiabatic Interfered Decoder for Differential Phase Shift Quantum Key

Under the quantum key distribution with differential phase-shift-keying protocol, the ultimate stability of the system is limited by the residual wavelength drift of the quantum-key carrier and the polarization/refractive-index/physical-length fluctuations induced by environmental thermal disturbance. To permanently overcome such a shortcoming, a 1-bit-delayed interferometric fiberized decoder with ultrastable visibility maintenance and long-term immunity to environmental perturbations is demonstrated by employing all polarization maintaining-fiber to construct an asymmetric-arm Mach-Zehnder interferometer, and surrounding such a delay-line interferometric decoder with thermal-isolated sponge and styrofoam container. Receiving the DPS-QKD bit-stream with a high sifting key rate and low bit-error ratio is approached by maintaining the high interfered visibility and eliminating the wavelength drift with a highly adiabatic package. Such an ultrastable long-term 1-bit delay interferometric decoder is particularly suitable for the persistent DPS-QKD operation towards future commercialization.