Hybrid quantum systems with trapped charged particles

TL;DR

This paper explores the theoretical feasibility of coupling trapped charged particles, especially electrons, with superconducting and mechanical systems to create hybrid quantum devices, highlighting potential advantages and technological challenges.

Contribution

It provides a comparative analysis of coupling rates and decoherence, identifying trapped electrons as promising candidates for hybrid quantum systems and discussing the experimental challenges involved.

Findings

Electron-based systems may achieve coupling rates exceeding decoherence.

Ion-based systems are less favorable due to slower coupling rates.

Technological challenges include trap design, electron sources, and cooling methods.

Abstract

We study theoretically the possibilities of coupling the quantum mechanical motion of a trapped charged particle (e.g. ion or electron) to quantum degrees of freedom of superconducting devices, nano-mechanical resonators and quartz bulk acoustic wave resonators. For each case, we estimate the coupling rate between the charged particle and its macroscopic counterpart and compare it to the decoherence rate, i.e. the rate at which quantum superposition decays. A hybrid system can only be considered quantum if the coupling rate significantly exceeds all decoherence rates. Our approach is to examine specific examples, using parameters that are experimentally attainable in the foreseeable future. We conclude that those hybrid quantum system considered involving an atomic ion are unfavorable, compared to using an electron, since the coupling rates between the charged particle and its counterpart are slower than the expected decoherence rates. A system based on trapped electrons, on the other hand, might have coupling rates which significantly exceed decoherence rates. Moreover it might have appealing properties such as fast entangling gates, long coherence and flexible electron interconnectivity topology. Realizing such a system, however, is technologically challenging, since it requires accommodating both trapping technology and superconducting circuitry in a compatible manner. We review some of the challenges involved, such as the required trap parameters, electron sources, electrical circuitry and cooling schemes in order to promote further investigations towards the realization of such a hybrid system.