Exchange-based two-qubit gate for singlet-triplet qubits

TL;DR

This paper proposes an exchange-based two-qubit gate for singlet-triplet qubits in quantum dots, demonstrating high fidelity and robustness against noise with adiabatic pulses and magnetic field gradients.

Contribution

It introduces a simple, single-pulse exchange gate design that suppresses leakage and maintains high fidelity under realistic experimental conditions.

Findings

High entanglement fidelities achievable with realistic parameters

Adiabatic pulses significantly reduce leakage compared to square pulses

Gate times comparable to single-qubit operations

Abstract

We analyse a simple exchange-based two-qubit gate for singlet-triplet qubits in gate-defined semiconductor quantum dots that can be implemented in a single exchange pulse. Excitations from the logical subspace are suppressed by a magnetic field gradient that causes spin-flip transitions to be non-energy-conserving. We show that the use of adiabatic pulses greatly reduces leakage processes compared to square pulses. We also characterise the effect of charge noise on the entanglement fidelity of the gate both analytically and in simulations; demonstrating high entanglement fidelities for physically realistic experimental parameters. Specifically we find that it is possible to achieve fidelities and gate times that are comparable to single-qubit states using realistic magnetic field gradients.