Optimizing the Frequency Positioning of Tunable Couplers in a Circuit QED Processor to Mitigate Spectator Effects on Quantum Operations
S. Vallés-Sanclemente (Kavli institute of nanoscience Delft, TU Delft - QCD/DiCarlo Lab, TU Delft - Qutech QIA)
T. H.F. Vroomans (Kavli institute of nanoscience Delft, TU Delft - Applied Sciences, TU Delft - QuTech Advanced Research Centre)
T. R. Van Abswoude (Orange Quantum Systems)
T. Stavenga (Quantware)
F. Brulleman (Quantware)
S. L.M. Van der Meer (Kavli institute of nanoscience Delft, TU Delft - QuTech Advanced Research Centre)
Y. Xin (TU Delft - QCD/DiCarlo Lab, Kavli institute of nanoscience Delft, TU Delft - QuTech Advanced Research Centre)
A. Lawrence (Orange Quantum Systems)
V. Singh (Kavli institute of nanoscience Delft, TU Delft - QuTech Advanced Research Centre)
M. A. Rol (TU Delft - BUS/Quantum Delft)
L. DiCarlo (TU Delft - QCD/DiCarlo Lab, TU Delft - Applied Sciences)
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Abstract
We experimentally optimize the frequency of flux-tunable couplers in a superconducting quantum processor to minimize the impact of spectator transmons during quantum operations (single-qubit gates, two-qubit gates, and readout) on other transmons. We adapt a popular transmonlike tunable-coupling element, achieving high-fidelity, low-leakage controlled-Z gates with unipolar, fast-adiabatic pulsing only on the coupler. We demonstrate the ability of the tunable coupler to null residual-ZZ coupling as well as exchange couplings in the one- and two-excitation manifolds. However, the nulling of these coherent interactions is not simultaneous, prompting the exploration of trade-offs. We present experiments pinpointing spectator effects on specific quantum operations. We also study the combined effect on the three types of operations using repeated quantum parity measurements.