Nonlinear Graphene Quantum Capacitors for Electro-optics

TL;DR

This paper explores the use of graphene quantum capacitors with nonlinear properties at cryogenic temperatures for applications in quantum electro-optics, demonstrating ultrastrong coupling and potential quantum device designs.

Contribution

It introduces a novel graphene-based nonlinear capacitor structure that enables ultrastrong coupling and quantum device functionalities at low temperatures.

Findings

Achieves ultrastrong coupling with few pump photons at 1K

Demonstrates nonlinear behavior suitable for quantum electro-optics

Proposes qubit and non-reciprocal device schemes

Abstract

Owing to its peculiar energy dispersion, the quantum capacitance property of graphene can be exploited in a two-dimensional layered capacitor configuration. Using graphene and boron nitride respectively as the electrodes and the insulating dielectric, a strongly nonlinear behavior at zero bias and small voltages is obtained. When the temperature is sufficiently low, the strong nonlinear interaction emerging from the quantum capacitance exhibits a diverse range of phenomena. The proposed structure could take over the functionalities of nonlinear elements in many cryogenic quantum systems, and in particular, quantum electro-optics. It is shown that ultrastrong coupling is easily reached with small number of pump photons at temperatures around 1K and capacitor areas of the order of $1\mu{\textrm{m}}^2$. A measure of anharmonicity is defined and as potential applications, a qubit design as well as schemes for non-reciprocal devices such as an electromagnetic frequency circulator are discussed.