Jellybean quantum dots in silicon for qubit coupling and on-chip quantum chemistry

TL;DR

This study explores silicon-based jellybean quantum dots as potential qubit couplers, demonstrating their charge and spin properties and their ability to form tunable artificial molecules suitable for scalable quantum processors.

Contribution

It provides experimental and simulation insights into the charge and spin behavior of elongated silicon quantum dots, highlighting their potential as qubit couplers in quantum computing architectures.

Findings

Formation of coupled quantum dots at low electron occupancy

Transition to a single large dot at high electron occupancy

Potential use of jellybean dots as qubit couplers

Abstract

The small size and excellent integrability of silicon metal-oxide-semiconductor (SiMOS) quantum dot spin qubits make them an attractive system for mass-manufacturable, scaled-up quantum processors. Furthermore, classical control electronics can be integrated on-chip, in-between the qubits, if an architecture with sparse arrays of qubits is chosen. In such an architecture qubits are either transported across the chip via shuttling, or coupled via mediating quantum systems over short-to-intermediate distances. This paper investigates the charge and spin characteristics of an elongated quantum dot -- a so-called jellybean quantum dot -- for the prospects of acting as a qubit-qubit coupler. Charge transport, charge sensing and magneto-spectroscopy measurements are performed on a SiMOS quantum dot device at mK temperature, and compared to Hartree-Fock multi-electron simulations. At low electron occupancies where disorder effects and strong electron-electron interaction dominate over the electrostatic confinement potential, the data reveals the formation of three coupled dots, akin to a tunable, artificial molecule. One dot is formed centrally under the gate and two are formed at the edges. At high electron occupancies, these dots merge into one large dot with well-defined spin states, verifying that jellybean dots have the potential to be used as qubit couplers in future quantum computing architectures.