Mitigating Residual Exchange Coupling in Resonant Singlet-Triplet Qubits

TL;DR

This paper introduces methods to reduce control errors caused by residual exchange coupling in resonant singlet-triplet qubits, including commensurate driving and coupler-based architectures, enhancing fidelity for scalable quantum computing.

Contribution

It proposes novel techniques like commensurate driving and single-spin couplers to mitigate residual exchange errors in singlet-triplet qubits, improving control fidelity and scalability.

Findings

Commensurate driving reduces intra-qubit exchange errors.

Single-spin couplers significantly decrease inter-qubit crosstalk.

Predicted two-qubit gate errors below 3×10^{-3} at 66 ns gate time.

Abstract

We propose methods to mitigate single- and two-qubit control errors due to residual exchange coupling in systems of exchange-coupled resonant singlet-triplet qubits. Commensurate driving, where the pulse length is an integer multiple of the drive period, can mitigate errors from residual intra-qubit exchange, including effects from counter rotating terms and off-axis rotations, as well as leakage errors during two-qubit operations. Residual inter-qubit exchange creates crosstalk errors that reduce single-qubit control fidelities. We show that using a single-spin coupler between two resonant singlet-triplet qubits can reduce this crosstalk error by an order of magnitude. Assuming perfect coupler state preparation and realistic charge and hyperfine noise, we predict that coupler-assisted two-qubit gate errors can be below $3\times10^{-3}$ for gate times as short as $66~\text{ns}$, even in the presence of residual exchange levels exceeding several hundred kHz. Our results suggest the potential of utilizing coupler-based architectures for large scale fault-tolerant spin qubit processors based on resonant singlet-triplet qubits.