Quantum information tapping using a fiber optical parametric amplifier with noise figure improved by correlated inputs

TL;DR

This paper demonstrates a fiber optical parametric amplifier with correlated inputs that reduces quantum noise through entanglement, enabling improved quantum information distribution compatible with existing telecom networks.

Contribution

It introduces a fiber-based quantum information tap using correlated inputs to reduce noise and surpass classical information transfer limits.

Findings

Noise figure improved by ~0.8 dB using correlated inputs

Total information transfer coefficient exceeds classical limit of 1

Device operates at 1550 nm telecom band

Abstract

One of the important function in optical communication system is the distribution of information encoded in an optical beam. It is not a problem to accomplish this in a classical system since classical information can be copied at will. However, challenges arise in quantum system because extra quantum noise is often added when the information content of a quantum state is distributed to various users. Here, we experimentally demonstrate a quantum information tap by using a fiber optical parametric amplifier (FOPA) with correlated inputs, whose noise is reduced by the destructive quantum interference through quantum entanglement between the signal and the idler input fields. By measuring the noise figure of the FOPA and comparing with a regular FOPA, we observe an improvement of 0.7+-0.1 dB and 0.84+-0.09 dB from the signal and idler outputs, respectively. When the low noise FOPA functions as an information splitter, the device has a total information transfer coefficient of Ts+Ti=1.47+-0.2, which is greater than the classical limit of 1. Moreover, this fiber based device works at the 1550 nm telecom band, so it is compatible with the current fiber-optical network.