Path-polarization hyperentangled and cluster states of photons on a chip

TL;DR

This paper demonstrates the generation and control of hyperentangled and cluster states of photons using integrated photonic circuits, advancing miniaturization and stability for quantum information processing.

Contribution

It introduces a method for creating and manipulating path-polarization hyperentangled and cluster states on a chip, enabling scalable quantum photonic technologies.

Findings

Successful generation of four-qubit linear cluster states on a chip

Demonstrated control of path and polarization degrees of freedom

Paved the way for fully integrated hybrid multiqubit photonic states

Abstract

Encoding many qubits in different degrees of freedom (DOFs) of single photons is one of the routes towards enlarging the Hilbert space spanned by a photonic quantum state. Hyperentangled photon states (i.e. states showing entanglement in multiple DOFs) have demonstrated significant implications for both fundamental physics tests and quantum communication and computation. Increasing the number of qubits of photonic experiments requires miniaturization and integration of the basic elements and functions to guarantee the set-up stability. This motivates the development of technologies allowing the precise control of different photonic DOFs on a chip. We demonstrate the contextual use of path and polarization qubits propagating within an integrated quantum circuit. We tested the properties of four-qubit linear cluster states built on both DOFs. Our results pave the way towards the full integration on a chip of hybrid multiqubit multiphoton states.