Coherent coupling between a quantum dot and a donor in silicon

TL;DR

This paper demonstrates coherent coupling between a phosphorus donor and a quantum dot in silicon, enabling new quantum bit interactions and control within a single device, advancing silicon-based quantum computing.

Contribution

It presents the first demonstration of coherent interaction between a donor electron and a quantum dot in silicon, enabling deterministic coupling and control of spin states.

Findings

Coherent interaction between a $^{31}$P donor and a quantum dot was achieved.

Donor nuclear spin enables coherent rotations of the electronic qubit.

The system forms a logical qubit using singlet and triplet states.

Abstract

Individual donors in silicon chips are used as quantum bits with extremely low error rates. However, physical realizations have been limited to one donor because their atomic size causes fabrication challenges. Quantum dot qubits, in contrast, are highly adjustable using electrical gate voltages. This adjustability could be leveraged to deterministically couple donors to quantum dots in arrays of qubits. In this work, we demonstrate the coherent interaction of a $^{31}$P donor electron with the electron of a metal-oxide-semiconductor quantum dot. We form a logical qubit encoded in the spin singlet and triplet states of the two-electron system. We show that the donor nuclear spin drives coherent rotations between the electronic qubit states through the contact hyperfine interaction. This provides every key element for compact two-electron spin qubits requiring only a single dot and no additional magnetic field gradients, as well as a means to interact with the nuclear spin qubit.