Quantum linear amplifier enhanced by photon subtraction and addition

TL;DR

This paper explores how photon subtraction, addition, and their superposition can probabilistically enhance quantum amplifiers, improving fidelity, gain, and phase uncertainty beyond deterministic limits.

Contribution

It introduces a heralded quantum amplifier that uses photon subtraction and addition to surpass traditional noise limits in quantum amplification.

Findings

Photon subtraction optimizes fidelity and phase concentration.

Photon addition significantly reduces phase uncertainty.

Combined operations enhance amplification performance.

Abstract

A deterministic quantum amplifier inevitably adds noise to an amplified signal due to the uncertainty principle in quantum physics. We here investigate how a quantum-noise-limited amplifier can be improved by additionally employing the photon subtraction, the photon addition, and a coherent superposition of the two, thereby making a probabilistic, heralded, quantum amplifier. We show that these operations can enhance the performance in amplifying a coherent state in terms of intensity gain, fidelity, and phase uncertainty. In particular, the photon subtraction turns out to be optimal for the fidelity and the phase concentration among these elementary operations, while the photon addition also provides a significant reduction in the phase uncertainty with the largest gain effect.