Electrons in quantum dots on helium: from charge qubits to synthetic color centers

TL;DR

This paper explores how electrons trapped on helium surfaces can serve as charge qubits and synthetic color centers, highlighting the effects of ripplon coupling on electron dynamics and the potential for tunable quantum systems.

Contribution

It introduces a detailed analysis of electron-ripplon interactions in helium-based quantum dots, revealing new regimes for studying color center physics and qubit implementation.

Findings

Strong electron-ripplon coupling can be achieved and controlled.

Coupling strength influences the feasibility of charge qubits.

Spectroscopy of synthetic color centers varies with coupling regime.

Abstract

Electrons trapped above the surface of helium provide a means to study many-body physics free from the randomness that comes from defects in other condensed-matter systems. Localizing an electron in an electrostatic quantum dot makes its energy spectrum discrete, with controlled level spacing. The lowest two states can act as charge qubit states. In this paper, we study how the coupling to the quantum field of capillary waves on helium -- ripplons -- affects electron dynamics. As we show, the coupling can be strong. This bounds the parameter range where electron-based charge qubits can be implemented. The constraint is different from the conventional relaxation time constraint. The electron-ripplon system in a dot is similar to a color center formed by an electron defect coupled to phonons in a solid. In contrast to solids, the coupling in the electron on helium system can be varied from strong to weak. This enables a qualitatively new approach to studying color center physics. We analyze the spectroscopy of the pertinent synthetic color centers in a broad range of the coupling strength