Two-qubit gates in silicon quantum dots*

Silicon spin qubits offer long coherence times and exquisite single-qubit control in a platform that has proven to be scalable by the semiconductor electronics industry. Despite these advantages, there are very few demonstrations of two-qubit gates [1-3]. By incorporating a micromagnet with a double quantum dot device, we have recently demonstrated a fast (<200 ns), resonantly-driven CNOT gate [2]. In the same device, we have also implemented a CPHASE gate by applying dc voltage pulses to the barrier gate separating the two qubits. In this talk, we will discuss the operation of the CPHASE and address complications due to the field gradient generated by the micromagnet. We compare the CPHASE operation to the resonantly-driven CNOT and estimate the corresponding two-qubit gate fidelities.

[1] M. Veldhorst et al., Nature 526, 410 (2015).
[2] D. M. Zajac et al., arXiv:1708.03530 (2017).
[3] T. F. Watson et al., arXiv:1708.04214 (2017).