A mathematical criterion for single photon sources used in quantum cryptography

TL;DR

This paper establishes a mathematical criterion for evaluating single photon sources in quantum cryptography, emphasizing the importance of nonclassical, higher order antibunched states, and examines four wave mixing as a potential candidate.

Contribution

It introduces a new mathematical criterion for higher order antibunching in single photon sources used in quantum cryptography.

Findings

Proposed a mathematical criterion for higher order antibunching.

Analyzed four wave mixing as a candidate for single photon source.

Highlighted the importance of nonclassical states in quantum cryptography.

Abstract

A single photon source (SPS) is very important for quantum computation. In particular, it is essential for secured quantum cryptography. But there is no perfect SPS in reality. Therefore, probabilistic SPS where probability of simultaneous emission of two, three, four and more photon is less than the emission of a single photon are used. Since classical photon always comes in bunch, the required single photon source must be nonclassical. In the well-known antibunched state the rate of simultaneous emission of two photon is less than that of single photon. But the requirement of quantum cryptography is a multiphoton version of the antibunched state or the higher order antibunched state. Recently we have reported a mathematical criterion for higher order antibunching. Here we have shown that any proposal for SPS to be used in quantum cryptography should satisfy this criterion. We have studied four wave mixing as a possible candidate of single photon source.