A simple scheme for expanding photonic cluster states for quantum information

TL;DR

This paper presents a practical method for expanding photonic cluster states by deterministically entangling polarization and path degrees of freedom, enabling scalable quantum information processing.

Contribution

It introduces a polarization-path controlled-phase gate and demonstrates its implementation for expanding cluster states in a stable, experimental setup.

Findings

Successful entanglement of polarization and path qubits using a Sagnac interferometer

Controlled phase manipulation enables measurement basis control

Experimental realization of properties of measurement-based quantum computing

Abstract

We show how an entangled cluster state encoded in the polarization of single photons can be straightforwardly expanded by deterministically entangling additional qubits encoded in the path degree of freedom of the constituent photons. This can be achieved using a polarization--path controlled-phase gate. We experimentally demonstrate a practical and stable realization of this approach by using a Sagnac interferometer to entangle a path qubit and polarization qubit on a single photon. We demonstrate precise control over phase of the path qubit to change the measurement basis and experimentally demonstrate properties of measurement-based quantum computing using a 2 photon, 3 qubit cluster state.