Universal singlet-triplet qubits implemented near the transverse sweet spot

TL;DR

This paper demonstrates high-fidelity single- and two-qubit gates for singlet-triplet qubits in semiconductor double quantum dots by operating near the transverse sweet spot and using noise-immune pulse sequences.

Contribution

It introduces a method to achieve over 99% fidelity for both single- and two-qubit gates near the transverse sweet spot in DQD-based singlet-triplet qubits.

Findings

Single-qubit gates achieved with AC drive on detuning near TSS.

Strong qubit-cavity coupling enables two-qubit entangling gates.

Fidelity of both gate types exceeds 99% with proper operation.

Abstract

The key to realizing fault-tolerant quantum computation for singlet-triplet (ST) qubits in semiconductor double quantum dot (DQD) is to operate both the single- and two-qubit gates with high fidelity. The feasible way includes operating the qubit near the transverse sweet spot (TSS) to reduce the leading order of the noise, as well as adopting the proper pulse sequences which are immune to noise. The single-qubit gates can be achieved by introducing an AC drive on the detuning near the TSS. The large dipole moment of the DQDs at the TSS has enabled strong coupling between the qubits and the cavity resonator, which leads to a two-qubit entangling gates. When operating in the proper region and applying modest pulse sequences, both single- and two-qubit gates are having fidelity higher than 99%. Our results suggest that taking advantage of the appropriate pulse sequences near the TSS can be effective to obtain high-fidelity ST qubits.