Detector decoy quantum key distribution

Tobias Moroder,Norbert Lütkenhaus,Marcos Curty

doi:10.1088/1367-2630/11/4/045008

Tobias Moroder, Norbert Lütkenhaus + Show 1 more

Open Access

https://doi.org/10.1088/1367-2630/11/4/045008

Copy DOI

Abstract

Photon number resolving detectors can enhance the performance of many practical quantum cryptographic setups. In this paper, we employ a simple method to estimate the statistics provided by such a photon number resolving detector using only a threshold detector together with a variable attenuator. This idea is similar in spirit to that of the decoy state technique, and is especially suited to those scenarios where only a few parameters of the photon number statistics of the incoming signals have to be estimated. As an illustration of the potential applicability of the method in quantum communication protocols, we use it to prove security of an entanglement-based quantum key distribution scheme with an untrusted source without the need for a squash model and by solely using this extra idea. In this sense, this detector decoy method can be seen as a different conceptual approach to adapt a single-photon security proof to its physical, full optical implementation. We show that in this scenario, the legitimate users can now even discard the double click events from the raw key data without compromising the security of the scheme, and we present simulations on the performance of the BB84 and the 6-state quantum key distribution protocols.

Highlights

Among the research performed nowadays in order to increase the secret key rate and distance that can be covered by quantum key distribution (QKD) systems, one can distinguish three main work areas which are closely related to each other [1, 2, 3]
We compare it with a security proof that relies on the validity of the squash model; for a different comparison between the squash model and an alternative estimation procedure not based in this last paradigm see Ref. [70]
We have shown that the detector decoy idea provides a simple method to adapt a single photon security proof to its full optical implementation, while still providing similar key rates as those arising from a security proof using the squash model assumption

Summary

Introduction

Among the research performed nowadays in order to increase the secret key rate and distance that can be covered by quantum key distribution (QKD) systems, one can distinguish three main work areas which are closely related to each other [1, 2, 3]. The use of photon number resolving (PNR) detectors instead of threshold detectors can enhance the performance of many practical QKD setups In those situations where the decoy state method cannot be applied. The central idea of the problem remains unchanged This method can be considered as the decoy state technique applied to the detector side: If Alice and Bob vary, independently and at random, the detection efficiency of their apparatus they can estimate the photon number statistics of the signals received. We apply this method to different practical QKD scenarios.

Estimating photon number statistics

Entanglement based QKD schemes with an untrusted source

Secret key rate

Detector decoy estimation

Evaluation

Conclusion and outlook