Quantum computing in a piece of glass

TL;DR

This paper proposes a novel approach to quantum computing using photonic diffraction in holographic glass, enabling quantum gates and algorithms with potential advantages in robustness and efficiency, though with scalability limitations.

Contribution

It introduces a holographic optical method for quantum gates based on photon diffraction and analyzes its theoretical and numerical performance using PTR glass.

Findings

High efficiency and robustness demonstrated in simulations

Potential for encoding entanglement in higher-dimensional states

Limitations in scalability and crosstalk identified

Abstract

Quantum gates and simple quantum algorithms can be designed utilizing the diffraction phenomena of a photon within a multiplexed holographic element. The quantum eigenstates we use are the photon's linear momentum (LM) as measured by the number of waves of tilt across the aperture. Two properties of quantum computing within the circuit model make this approach attractive. First, any conditional measurement can be commuted in time with any unitary quantum gate - the timeless nature of quantum computing. Second, photon entanglement can be encoded as a superposition state of a single photon in a higher-dimensional state space afforded by LM. Our theoretical and numerical results indicate that OptiGrate's photo-thermal refractive (PTR) glass is an enabling technology. We will review our previous design of a quantum projection operator and give credence to this approach on a representative quantum gate grounded on coupled-mode theory and numerical simulations, all with parameters consistent with PTR glass. We discuss the strengths (high efficiencies, robustness to environment) and limitations (scalability, crosstalk) of this technology. While not scalable, the utility and robustness of such optical elements for broader quantum information processing applications can be substantial.