RF Reflectometry of the Rydberg State of Electrons on Helium: Towards a Helium-Based Quantum Computer

Surface electrons (SEs) on liquid helium present a promising candidate for scalable quantum computing. We propose to use a hybrid qubit by coupling the spin state of the SE to the hydrogen-like Rydberg state [1]. A SE can be trapped above the surface of a thin superfluid helium film using a nanofabricated device beneath the surface. A gradient magnetic field can then be created by a ferromagnet placed nearby to couple the Rydberg and spin state of the trapped SE. Two SEs can be placed close to each other, and a two-qubit gate can be performed using the Coulomb interaction.

In order to perform the readout of the qubit state, it is imperative to detect the Rydberg state of an individual SE. For this purpose, we employ a high Q-factor LC resonator for RF reflectometry, a technique previously established for electrons in semiconductors [2]. We experimentally validated the feasibility of this approach with an ensemble of many SEs and are now advancing our efforts to implement this technique for a single SE.



[1] E. Kawakami, et al. arXiv:2303.03688 [2] G. A. Oakes, et al. Phys. Rev. X 13, 011023 (2023)