Electron spin coherence on a solid neon surface

TL;DR

This study theoretically investigates electron spin coherence on solid neon surfaces, revealing potential for long coherence times suitable for quantum computing, especially with isotopically purified neon.

Contribution

It provides the first detailed theoretical analysis of electron spin decoherence mechanisms on solid neon, including experimental relevance and potential for long-lived qubits.

Findings

Inhomogeneous dephasing time T2* is ~0.16 ms for natural Ne and 0.43 s for purified Ne.

Hahn echo techniques can extend coherence time T2 to 30 ms (natural Ne) and 81 s (purified Ne).

Electron spin coherence on solid Ne exceeds many semiconductor qubits, promising for quantum applications.

Abstract

A single electron floating on the surface of a condensed noble-gas liquid or solid can act as a spin qubit with ultralong coherence time, thanks to the extraordinary purity of such systems. Previous studies suggest that the electron spin coherence time on a superfluid helium (He) surface can exceed 100 s. In this paper, we present theoretical studies of the electron spin coherence on a solid neon (Ne) surface, motivated by our recent experimental realization of single-electron charge qubit on solid Ne. The major spin decoherence mechanisms investigated include the fluctuating Ne diamagnetic susceptibility due to thermal phonons, the fluctuating thermal current in normal metal electrodes, and the quasi-statically fluctuating nuclear spins of the $^{21}$Ne ensemble. We find that at a typical experimental temperature about 10 mK in a fully superconducting device, the electron spin decoherence is dominated by the third mechanism via electron-nuclear spin-spin interaction. For natural Ne with 2700 ppm abundance of $^{21}$Ne, the estimated inhomogeneous dephasing time $T_{2}^{*}$ is around 0.16 ms, already better than most semiconductor quantum-dot spin qubits. For commercially available, isotopically purified Ne with 1 ppm of $^{21}$Ne, $T_{2}^{*}$ can be $0.43$ s. Under the application of Hahn echoes, the coherence time $T_{2}$ can be improved to $30$ ms for natural Ne and $81$ s for purified Ne. Therefore, the single-electron spin qubits on solid Ne can serve as promising new spin qubits.