Electrons on helium form a two dimensional electron gas (2DEG) with exceptional properties including the highest known electron mobility and spin coherence times predicted to exceed 100s. For these reasons one of first quantum computing proposals considered using the vertical motional states of electrons on helium[6], but progress has been slow because of prohibitive (>100 GHz) transition frequencies and difficulty in detection.
Integrating techniques from circuit QED, we can solve these problems by using a superconducting cavity (at a few GHz) to non-destructively measure the lateral motional state of the bound electron. We plan to build quantum dots on helium containing small numbers down to single electrons. These dots would be sufficiently small (sub-micron) that both the lateral spatial confinement and potential depth will determine the orbital properties. In addition, the electron's spin degree of freedom should be accessible. With this new technique, we hope to observe the coherent motion of a single electron on helium for the first time. The cavity will not only be used to interrogate the electron but also as a quantum bus to transfer the electron’s coherence to microwave photons, and to superconducting qubits. Initial theoretical calculations performed in collaboration with Mark Dykman at Michigan State, predict that the motional state should be long lived and coherent (T1 ~ T2>100s) while the electron-photon coupling rates can exceed (g > 10 MHz), allowing one to access the strong coupling regime of cavity QED and perform many gates[4].
