Controlling a superconducting nanowire single-photon detector using tailored bright illumination

Lars Lydersen,A Hamed Majedi,Johannes Skaar,Vadim Makarov,Mohsen K Akhlaghi

doi:10.1088/1367-2630/13/11/113042

Abstract

We experimentally demonstrate that a superconducting nanowire single-photon detector is deterministically controllable by bright illumination. We found that bright light can temporarily make a large fraction of the nanowire length normally conductive, can extend deadtime after a normal photon detection, and can cause a hotspot formation during the deadtime with a highly nonlinear sensitivity. As a result, although based on different physics, the superconducting detector turns out to be controllable by virtually the same techniques as avalanche photodiode detectors. As demonstrated earlier, when such detectors are used in a quantum key distribution system, this allows an eavesdropper to launch a detector control attack to capture the full secret key without this being revealed by too many errors in the key.

Highlights

Quantum key distribution (QKD) allows two parties, Alice and Bob, to generate a secret random key at a distance [1,2,3,4]
We experimentally demonstrate that a superconducting nanowire single-photon detector is deterministically controllable by bright illumination
With actual devices deviating from the ideal models, numerous security loopholes have been identified and usually experimentally confirmed [16,17,18,19,20,21,22,23,24,25,26,27], and in some cases exploited in eavesdropping experiments with full secret key extraction by Eve [28, 29]

Summary

INTRODUCTION

Quantum key distribution (QKD) allows two parties, Alice and Bob, to generate a secret random key at a distance [1,2,3,4]. With actual devices deviating from the ideal models, numerous security loopholes have been identified and usually experimentally confirmed [16,17,18,19,20,21,22,23,24,25,26,27], and in some cases exploited in eavesdropping experiments with full secret key extraction by Eve [28, 29]. Superconducting nanowire single-photon detectors (SNSPDs) studied in this paper are based on different physics. Regardless of whether the control mechanisms we have identified apply to other detector designs, our experiment shows that the bright illumination response of the SNSPD is deviating from the detector model in the simple security proofs for QKD.

DETECTOR DESIGN AND OPERATION

Physics

Exploit

DETECTOR CONTROL VIA DEADTIME EXTENSION

DISCUSSION AND CONCLUSION