APS March Meeting 2021

Spectators Errors in Multiqubit Tunable Coupling Architectures

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The addition of tunable couplers to superconducting quantum architectures offers significant advantages for scalability compared to fixed coupling approaches. Couplers such as the one proposed in Ref. [1] allow exact cancellation of qubit-qubit coupling by interfering the coupling through a capacitor with the coupling through a tunable qubit. However, the cancellation is necessarily narrowband, and in a multiqubit environment with stray couplings the cancellation condition can change depending on which gate is operating and even the states of the qubits. Here we investigate a modified version Ref. [1] coupler in multiqubit environment. With near-detuned qubits, we find that stray coupling can induce gate errors of order 1% when performing simultaneous gates if the microwave crosstalk is not carefully engineered. [1] F. Yan et al. Phys. Rev. Applied. 10, 054063 (2018)