Theory of Photon Subtraction for Two-Mode Entangled Light Beams

TL;DR

This paper develops a theoretical model for photon subtraction in two-mode entangled light beams, enabling precise predictions of the resulting nonclassical states and analyzing their properties in quantum photonics.

Contribution

It introduces a novel theoretical framework based on two-mode SU(2) coherent states for modeling photon subtraction in entangled light, providing explicit formulas and analysis tools.

Findings

Photon subtraction does not generate nonclassical fields from classical inputs.

Derived a compact expression for the output field enabling straightforward probability calculations.

Analyzed the effects of photon subtraction on squeezed-vacuum and odd-squeezed states.

Abstract

Photon subtraction is useful to produce nonclassical states of light addressed to applications in photonic quantum technologies. After a very accelerated development, this technique makes possible obtaining either single photons or optical cats on demand. However, it lacks theoretical formulation enabling precise predictions for the produced fields. Based on the representation generated by the two-mode $SU(2)$ coherent states, we introduce a model of entangled light beams leading to the subtraction of photons in one of the modes, conditioned to the detection of any photon in the other mode. We show that photon subtraction does not produce nonclassical fields from classical fields. It is also derived a compact expression for the output field from which the calculation of conditional probabilities is straightforward for any input state. Examples include the analysis of squeezed-vacuum and odd-squeezed states. We also show that injecting optical cats into a beam splitter gives rise to entangled states in the Bell representation.