Microwave response of electrically driven spins in a three-qubit quantum processor

TL;DR

This study investigates the microwave response of three-qubit spin systems in a quantum processor, demonstrating linear Rabi frequency scaling and clarifying previous nonlinear response reports, thus supporting reliable quantum control.

Contribution

The paper provides detailed measurements showing linear Rabi frequency scaling in multi-spin systems, challenging prior reports of nonlinearities in similar quantum devices.

Findings

Rabi frequency scales linearly with microwave drive amplitude

Heating effects cause resonance frequency shifts comparable to drifts

Nonlinear responses are not inherent to Loss-DiVincenzo spin qubits

Abstract

In electric dipole spin resonance (EDSR), a single spin is electrically driven in the field gradient produced by a micromagnet. While EDSR has enabled high fidelity gate operations in many devices, there are reports of unexpected non-linearities in the Rabi frequency as a function of microwave drive amplitude. We carefully measure the response of Loss-DiVincenzo (LD) single spin qubits to resonant drives as well as simultaneous resonant and off-resonant drives, as would be encountered in a realistic quantum processor. With the microwave amplitude carefully calibrated, we find that the Rabi frequency scales linearly with drive amplitude, even when all three spins are driven simultaneously. We also determine that heating-induced resonance frequency shifts from off-resonant drives are comparable to typical temporal drifts. Our results indicate that the previously observed nonlinear response is not a general feature of LD spin qubits.