Quantum key distribution over a 72 dB channel loss using ultralow dark count superconducting single-photon detectors

TL;DR

This paper demonstrates quantum key distribution over a 72 dB loss channel using ultralow dark count superconducting detectors, achieving secure key generation over 336 km of fiber.

Contribution

First experimental QKD over 72 dB loss with superconducting detectors and a differential phase shift scheme, enhancing long-distance quantum communication.

Findings

Achieved QBER below 3% at 336 km fiber length.

Used superconducting nanowire detectors with 0.01 cps dark count rate.

Successfully generated secure keys over a 72 dB channel loss.

Abstract

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.