Tunable Coupling Devices

Coupling qubits to each other or to the environment often results in various unwanted interactions. We achieve suppression of these interactions by harnessing quantum interference between different components in a carefully engineered architecture. This has been demonstrated in cancellation of shot noise dephasing due to thermal populations of the readout resonator and in tuning out of ZZ crosstalk between two coupled qubits.

Related Publications

Suppression of Qubit Crosstalk in a Tunable Coupling Superconducting Circuit
P. S. Mundada, G. Zhang, T. Hazard, and A. A. Houck, “Suppression of Qubit Crosstalk in a Tunable Coupling Superconducting Circuit,” Physics Review Applied, vol. 12, pp. 054023, 2018. Publisher's VersionAbstract
We report the suppression of static ZZ crosstalk in a two-qubit, two-coupler superconducting circuit, where the ZZ interaction between the two qubits can be tuned to near zero. Characterization of qubit crosstalk is performed using randomized benchmarking and a two-qubit iSWAP gate is implemented using parametric modulation. We observe the dependence of single-qubit gate fidelity on ZZ interaction strength and identify effective thermalization of the tunable coupler as a crucial prerequisite for high fidelity two-qubit gates.
Suppression of photon shot noise dephasing in a tunable coupling superconducting qubit
G. Zhang, Y. Liu, J. J. Raftery, and A. A. Houck, “Suppression of photon shot noise dephasing in a tunable coupling superconducting qubit,” npj Quantum Information, vol. 3, pp. 1, 2017. Publisher's VersionAbstract
We demonstrate the suppression of photon shot noise dephasing in a superconducting qubit by eliminating its dispersive coupling to the readout cavity. This is achieved in a tunable coupling qubit, where the qubit frequency and coupling rate can be controlled independently. We observe that the coherence time approaches twice the relaxation time and becomes less sensitive to thermal photon noise when the dispersive coupling rate is tuned from several MHz to 22 kHz. This work provides a promising building block in circuit quantum electrodynamics that can hold high coherence and be integrated into larger systems.