Confining Electrons Floating on Helium in Sub-Micron Quantum Dot Arrays

The semiconductor quantum dot community’s recent success in performing high fidelity single- and two-qubit^[1] logical operations has brought the electron spin state to the forefront of quantum information. The decoherence free nature of an electron floating on helium makes it an attractive solution to mitigating decoherence limitations inherent to host semiconductors crystals such as low-lying valley states and nuclear spin-spin interactions. However, the first step in realizing a spin qubit is reliably confining and controlling the charge degree of freedom of a single electron. Previous demonstrations in confinement have been successful in adding electrons and detecting single transitions in quantum dots on the order of 1-5 μm^[2], over an order of magnitude larger than a single electron wavefunction. The large dots make it difficult to spatially pinpoint and precisely manipulate charges both of which are requirements for high fidelity qubit operation. With this in mind, we fabricate multiple arrays containing millions of highly uniform, sub-micron quantum dots and explore the effect that dot size has on the electron confinement.

[1] Mills, A. R. et al. Two-qubit silicon quantum processor with operation fidelity exceeding 99%. Sci. Adv. 8, eabn5130 (2022).

[2] Papageorgiou, G. et. al. Counting individual trapped electrons on liquid helium. Applied Physics Letters 86, 153106 (2005).