Noise-Powered Probabilistic Concentration of Phase Information

TL;DR

This paper demonstrates a probabilistic quantum amplifier that uses thermal noise and photon subtraction to surpass the fundamental noise limit, achieving noiseless amplification with reduced phase uncertainty, which could benefit quantum metrology and communication.

Contribution

It introduces a novel probabilistic amplification method that leverages thermal noise and photon subtraction to beat the quantum noise limit.

Findings

Achieved noiseless amplification with phase uncertainty below the initial state.

Utilized thermal noise source combined with photon subtraction scheme.

Surprisingly, added incoherent noise can reduce phase uncertainty.

Abstract

Phase insensitive optical amplification of an unknown quantum state is known to be a fundamentally noisy operation that inevitably adds noise to the amplified state [1 - 5]. However, this fundamental noise penalty in amplification can be circumvented by resorting to a probabilistic scheme as recently proposed and demonstrated in refs [6 - 8]. These amplifiers are based on highly non-classical resources in a complex interferometer. Here we demonstrate a probabilistic quantum amplifier beating the fundamental quantum limit utilizing a thermal noise source and a photon number subtraction scheme [9]. The experiment shows, surprisingly, that the addition of incoherent noise leads to a noiselessly amplified output state with a phase uncertainty below the uncertainty of the state prior to amplification. This amplifier might become a valuable quantum tool in future quantum metrological schemes and quantum communication protocols.