Optimizing the electron-ripplon coupling for quantum computing with electrons on helium.

Single electrons bound to the surface of liquid helium are a promising new quantum computing platform [1]. These qubits are well isolated from the environment and decohere primarily through interactions with the vibrational modes of the liquid helium (ripplons and phonons). Here we consider the decay and dephasing rates of spin qubits. Of interest is the situation where the spin states are tuned in such a way that the Larmor frequency is close to the frequency of the orbital transition. In this case, the relaxation rates are determined by the coupling to surface capillary waves which mix the spin and orbital states [2]. We argue that current qubit devices are limited by dephasing. We show that the strength of the relevant coupling is controlled through the surface pressing field. The results provide guidance to improve future qubit devices.

[1] Platzman, P. M., & Dykman, M. I. (1999). Quantum computing with electrons floating on liquid helium. Science, 284(5422), 1967-1969.

[2] Dykman, M. I., Asban, O., Chen, Q., Jin, D., & Lyon, S. A. (2023). Spin dynamics in quantum dots on liquid helium. Physical Review B, 107(3), 035437.