Piezoacoustics for precision control of electrons floating on helium

Abstract

Piezoelectric surface acoustic waves (SAWs) are powerful for investigating and controlling elementary and collective excitations in condensed matter. In semiconductors SAWs have been used to reveal the underlying spatial and temporal structure of quantum phases of electronic matter [1-3], produce quantized charge pumping [4], transfer quantum information [5], and coherently control single electron states [6], culminating in the possibility of SAW-driven electronic flying qubits [7].However important challenges remain in protecting the coherence of propagating electrons from uncontrolled background nuclear spins, chemical dopants and spin-orbit crystal fields [8]. In contrast, electrons trapped on the surface of superfluid helium form a ultra-clean low-dimensional electron system devoid of the imperfections limiting the coherence in semiconductors. However, SAWs have not, to-date, been employed to manipulate electrons in this system or to explore the development of flying-qubits. Additionally, electrons on helium form strongly-interacting Coulomb liquid and solid states having collective dynamics that can couple to SAWs. Here we report on the first coupling of electrons on helium to an evanescent piezoelectric SAW. The electrons surf with the piezoelectric wave and we demonstrate high-frequency charge pumping in this system for the first time. With this piezoacoustic method we can precisely transport as little as ∼ 0.01% of the total electron density, opening the door to quantized charge pumping, the possibility of electrical metrology, and ultimately single electron state transfer with electrons on helium. We also show that SAWs are a route to directly investigating the high-frequency dynamical response, and relaxational processes, of collective excitations of the electronic liquid and solid phases of electrons on helium.

Low-temperature environments for quantum computation and quantum simulation*

“…The qubits based on electrons on helium [167,168] are very similar to those based on quantum dots. Both the two lowest energy levels and the spin of the electron can be utilized to construct qubits [167][168][169][170][171] . The electrons can stay on the surface of superfluid 4 He, which may hold the record of the highest mobility among two-dimensional transport systems [172] .…”

“…Both the two lowest energy levels and the spin of the electron can be utilized to construct qubits. [167][168][169][170][171] The electrons can stay on the surface of superfluid 4 He, which may hold the record of the highest mobility among two-dimensional transport systems. [172] Superconducting qubits are formed in superconducting quantum circuits comprising capacitors, inductors, and Josephson junctions, where artificial energy levels can be engineered.…”

Many-electron system on helium and the color center spectroscopy

“…The physics of point defects and the defect spectroscopy have been in the focus of attention recently in the context of quantum computing and quantum sensing [14]. On their side, electrons on helium themselves have been also considered as a viable candidate system for a scalable quantum computer [15][16][17][18][19].…”