Quantum key distribution over a 72 dB channel loss using ultralow dark count superconducting single-photon detectors
This enables long-distance secure quantum communication for applications like cryptography, though it is incremental as it builds on existing QKD methods with improved detectors.
The authors tackled the challenge of achieving secure quantum key distribution over extremely high channel loss by using ultralow dark count superconducting single-photon detectors, resulting in a quantum bit error rate below 3% over 336 km of fiber with 72 dB loss.
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 differential phase shift QKD (DPS-QKD) scheme with a 1 GHz system clock rate. The quantum bit error rate (QBER) below 3 % is achieved when the length of the dispersion shifted fiber (DSF) is 336 km (72 dB loss), which is low enough to generate secure keys.