Characterization of a spatial light modulator as a polarization quantum channel

TL;DR

This paper uses quantum information formalism to characterize how spatial light modulators act as polarization quantum channels, revealing their potential to couple polarization and spatial degrees of freedom for advanced quantum applications.

Contribution

It introduces a quantum process tomography method to model the effect of spatial light modulators on polarization states, enabling new ways to utilize these devices in quantum information processing.

Findings

Developed an analytic model for the quantum channel of a spatial light modulator.

Demonstrated a controllable phase flip channel using the device.

Showcased the coupling of polarization and spatial degrees of freedom.

Abstract

Spatial light modulators are versatile devices employed in a vast range of applications to modify the transverse phase or amplitude profile of an incident light beam. Most experiments are designed to use a specific polarization which renders optimal sensitivity for phase or amplitude modulation. Here we take a different approach and apply the formalism of quantum information to characterize how a phase modulator affects a general polarization state. In this context, the spatial modulators can be exploited as a resource to couple the polarization and the transverse spatial degrees of freedom. Using a quasi-monochromatic single photon beam obtained from a pair of twin photons generated by spontaneous parametric down conversion, we performed quantum process tomography in order to obtain a general analytic model for a quantum channel that describes the action of the device on the polarization qubits. We illustrate the application of these concepts by demonstrating the implementation of a controllable phase flip channel. This scheme can be applied in a straightforward manner to characterize the resulting polarization states of different types of phase or amplitude modulators and motivates the combined use of polarization and spatial degrees of freedom in innovative applications.