How subtraction of a single photon affects many quantum modes

TL;DR

This paper develops a unified theoretical framework to analyze how subtracting a single photon from multimode quantum fields affects their quantum states, with implications for scalable quantum information processing.

Contribution

It introduces the concept of subtraction modes and provides conditions for pure photon subtraction in multimode fields, advancing understanding of multimode quantum state manipulation.

Findings

Identifies conditions for pure photon subtraction in multimode fields

Defines subtraction modes intrinsic to the process

Analyzes photon subtraction from multimode squeezed light

Abstract

The subtraction of a single photon from a multimode quantum field is analyzed as the conditional evolution of an open quantum system. We develop a theory describing different subtraction schemes in a unified approach and we introduce the concept of subtraction modes intrinsic to the process. The matching between the subtraction modes and the modes of the field defines different possible scenarios for the photon subtraction. In particular, our framework identifies: the conditions of pure photon subtraction, the quantum states of the field modes conditioned to the photon subtraction, the mode with the highest fidelity with a single-photon state when the subtraction is performed on multimode squeezed light. We use our theory to analyze the photon subtraction from a highly multimode quantum resource - a train of quantum squeezed or correlated optical pulses. Performing the photon subtraction optimally on various multimode light field has the potential to implement a number of quantum information protocols in a multiplexed and scalable way.