# Mode-Dependent Loss Model for Multimode Photon-Subtracted States

## TL;DR

This paper models how mode-dependent optical losses affect multimode photon-subtracted quantum states, revealing that losses alter the state's non-Gaussian features and modal structure, which is crucial for quantum optics experiments.

## Contribution

It introduces a comprehensive open quantum systems model for losses in multimode photon-subtracted states, highlighting the non-commuting nature of losses and photon subtraction.

## Key findings

- Losses do not commute with photon subtraction, affecting state purity.
- Losses alter the modal structure of non-Gaussian features.
- Single-photon subtraction in multimode states is experimentally feasible.

## Abstract

Multimode photon-subtraction provides an experimentally feasible option to construct large non-Gaussian quantum states in continuous-variable quantum optics. The non-Gaussian features of the state can lead towards the more exotic aspects of quantum theory, such as negativity of the Wigner function. However, the pay-off for states with such delicate quantum properties is their sensitivity to decoherence. In this paper, we present a general model that treats the most important source of decoherence in a purely optical setting: losses. We use the framework of open quantum systems and master equations to describe losses in n-photon-subtracted multimode states, where each photon can be subtracted in an arbitrary mode. As a main result, we find that mode-dependent losses and photon-subtraction generally do not commute. In particular, the losses do not only reduce the purity of the state, they also change the modal structure of its non-Gaussian features. We then conduct a detailed study of single-photon subtraction from a multimode Gaussian state, which is a setting that lies within the reach of present-day experiments.