General U(4) gate for photon polarization and orbital angular momentum

TL;DR

This paper proposes a method to implement a universal U(4) quantum gate for photons using polarization and orbital angular momentum, promising high fidelity operations limited only by losses.

Contribution

It introduces a new scheme for U(4) gates that surpasses previous q-plate based methods by enabling near-perfect transformations limited solely by losses.

Findings

Scheme achieves higher fidelity than previous methods

The approach is scalable for complex quantum photonic circuits

Potential for near-perfect quantum gate operations

Abstract

We examine the implementation of an arbitrary U(4) gate consisting of CNOT gates and single qubit unitary gates for the Hilbert space of photon spin polarization and two states of photon orbital angular momentum. Our scheme improves over a recently proposed one that uses q-plates because the fidelity is limited only by losses thus in principle it could be used to achieve a perfect transformation.