Solve single photon detector problems

TL;DR

This paper introduces a practical scheme using current technologies to mitigate single photon detector issues, significantly extending quantum key distribution distances by reducing dark count errors without requiring advanced detectors.

Contribution

It proposes a novel method to circumvent the no-cloning theorem in specific tasks, enabling multiple uses of a single quantum state with imperfect detectors to improve QBER and detection efficiency.

Findings

QKD distance can be extended from hundreds to thousands of kilometers.

Dark count-induced QBER can be reduced to arbitrarily low levels.

Imperfect detectors can achieve near-perfect measurement results.

Abstract

Single photon detector(SPD) problems arise in most quantum tasks, especially for measuring states going through high-lost channels. They are particularly prominent in quantum key distribution(QKD), which could be the most significant application in quantum information theory. In recent years, QKD distance has been improved dramatically but is still restricted because the bit error rate(QBER) caused by SPD dark counts will be out of control as the distance increases. If this problem can be solved, QKD can be implemented over arbitrarily long distances. However, previous solutions often result in impractical requirements such as superconductors while they can only reduce the dark count rate to finite low levels. In this paper, we solve SPD problems with today's technologies only. Although it is the no-cloning theorem that prevents a state from being measured multiple times to obtain a more reliable result, we propose a scheme circumventing the no-cloning theorem in certain tasks to allow a single state to be employed several times. The scheme demonstrates that imperfect detectors can provide nearly perfect results, namely, the QBER caused by dark counts can be reduced to arbitrarily low while in the meantime, detective efficiency can be improved to arbitrarily high. Consequently, QKD distance is not limited by the imperfect SPD anymore and can be improved from hundreds of kilometers to thousands without high-technology detectors. Furthermore, similar schemes can be applied for reducing measurement errors or improving the performance of sources. Finally, it is worth noting that although the paper is mainly discussed in the context of QKD, our scheme is an independent scheme that could be employed in other protocols wherever SPD are employed.