Multi-photon tolerant secure quantum communication — From theory to practice

Abstract

Contemporary implementations of Quantum Key Distribution are based on BB84, first proposed in 1984, and commercially implemented for limited market applications in the early 2000s. A major limitation of BB84 is that it requires no more than a single photon per time slot. But no device can reliably generate single photons with guaranteed periodicity. In this paper, we address the practical issues of realizing quantum cryptography systems. In particular, we address the major shortcomings of quantum cryptography as practiced today - the limitation of requiring a single photon to be used in communication. This not only affects the security of the practical quantum cryptography systems, but also restricts the distance over which secure keys can be sent and their rate. Our approach is not limited to a single photon per time-slot thus making it possible to send keys faster and over longer distances. The paper discusses the innate nature of multi-photon communication protocols as a surrogate for quantum communication while giving it a cryptographic strength that would closely match that of a pure quantum communication system.