The path to high fidelity multi-qubit gates for quantum dot spin qubits*

Spin qubits in silicon quantum dots are a promising platform for quantum computation due to long decoherence times and fast operations. Demonstrations of single qubit gates show fidelities up to 99.9% [1] and two-qubit gates show fidelities of 92-98% [1,2]. These two-qubit gate implementations are not robust against low-frequency charge noise, which couples in via the exchange interaction. Furthermore, the limited bandwidth of the signals, diabatic errors, and microwave-crosstalk are additional error sources which have to be considered.

We show that advanced pulse shaping techniques commonly used for superconducting qubits [3] can be used to significantly improve the fidelities and the quality factor of gate operations. Furthermore, we propose a simple yet effective scheme for a decoupled version of a driven exchange gate [4] that is resilient against low-frequency charge noise. We use analytic calculations and numerical simulations under realistic conditions to verify gate fidelities greater than 99.9%, which allow for fault-tolerant gates.

[1] Huang et al., Nature (London) 569, 532 (2019)
[2] Xu et al., Phys. Rev. X 9, 021011 (2019)
[3] Motzoi et al., Phys. Rev. Lett. 103, 110501 (2009)
[4] Sigillito et al., npj Quantum Information 5 (1), 1 (2019)