Six-qubit two-photon hyperentangled cluster states: characterization and application to quantum computation

TL;DR

This paper characterizes six-qubit hyperentangled cluster states across multiple degrees of freedom and demonstrates their application in high-fidelity quantum gates, advancing towards scalable quantum computing.

Contribution

It introduces a detailed analysis of multi-degree of freedom cluster states and their use in implementing high-fidelity CNOT gates for quantum computation.

Findings

High-fidelity CNOT gates achieved using six-qubit hyperentangled states.

Demonstration of entanglement properties across polarization and momentum.

Potential for scalable quantum computation with multi-photon, multi-degree states.

Abstract

Six-qubit cluster states built on the simultaneous entanglement of two photons in three independent degrees of freedom, i.e. polarization and a double longitudinal momentum, have been recently demonstrated. We present here the peculiar entanglement properties of the linear cluster state $\LCtilde$ related to the three degrees of freedom. This state has been adopted to realize various kinds of Controlled NOT (CNOT) gates, obtaining in all the cases high values of the gate fidelity. Our results demonstrate that a number of qubits $\leq$10 in cluster states of two photons entangled in multiple degrees of freedom is achievable. Furthermore, these states represent a promising approach towards scalable quantum computation in a medium term time scale. The future perspectives of a hybrid approach to one-way quantum computing based on multi-degree of freedom and multi-photon cluster states are also discussed in the conclusions of this paper.