A high-gain and high-fidelity coherent statecomparison amplifier

Optical signals are subject to a distance-dependent loss as they propagate through trans-mission media. High-intensity, classical, optical signals can routinely be amplified to over-come the degradation caused by this loss. However, quantum optical states cannot bedeterministically amplified and any attempt to do so will introduce intrinsic noise that spoilsthe desired quantum properties. Non-deterministic optical amplification, based on post-selection of the output depending on certain conditioning detection outcomes, is an emergingenabling technology in quantum measurement and quantum communications. Here wepresent an investigation into the properties of a simple, modular optical state comparisonamplifier operating on weak coherent states. This amplifier requires no complex quantumresources and is based on linear optical components allowing for a high amplification rate athigh gain andfidelity. We examine the amplifier’s performance in different configurations anddevelop an accurate analytical model that accounts for typical experimental scenarios.