We introduce a circuit-QED architecture combining fixed-frequency qubits and microwave-driven couplers. In the appropriate frame, the drive parameters appear as tunable knobs enabling selective two-qubit coupling and coherent-error suppression. We moreover introduce a set of controlled-phase gates based on drive-amplitude and drive-frequency modulation. We develop a theoretical framework based on Floquet theory to model microwave-activated interactions with time-dependent drive parameters, which we also use for pulse shaping. We perform numerical simulations of the gate fidelity for realistic circuit parameters, and discuss the impact of drive-induced decoherence. We estimate average gate fidelities beyond $99.9\%$ for all-microwave controlled-phase operations with gate times in the range $50-120\,\mathrm{ns}$ . These two-qubit gates can operate over a large drive-frequency bandwidth and in a broad range of circuit parameters, thereby improving extensibility. We address the frequency allocation problem for this architecture using perturbation theory, demonstrating that qubit, coupler and drive frequencies can be chosen such that undesired static and driven interactions remain bounded in a multi-qubit device. Our numerical methods are useful for describing the time-evolution of driven systems in the adiabatic limit, and are applicable to a wide variety of circuit-QED setups.We introduce a circuit-QED architecture combining fixed-frequency qubits and microwave-driven couplers. In the appropriate frame, the drive parameters appear as tunable knobs enabling selective two-qubit coupling and coherent-error suppression. We moreover introduce a set of controlled-phase gates based on drive-amplitude and drive-frequency modulation. We develop a theoretical framework based on Floquet theory to model microwave-activated interactions with time-dependent drive parameters, which we also use for pulse shaping. We perform numerical simulations of the gate fidelity for realistic circuit parameters, and discuss the impact of drive-induced decoherence. We estimate average gate fidelities beyond $99.9\%$ for all-microwave controlled-phase operations with gate times in the range $50-120\,\mathrm{ns}$. These two-qubit gates can operate over a large drive-frequency bandwidth and in a broad range of circuit parameters, thereby improving extensibility. We address the frequency allocation problem for this architecture using perturbation theory, demonstrating that qubit, coupler and drive frequencies can be chosen such that undesired static and driven interactions remain bounded in a multi-qubit device. Our numerical methods are useful for describing the time-evolution of driven systems in the adiabatic limit, and are applicable to a wide variety of circuit-QED setups.

arXiv:2204.08098Apr 17, 20225 citations

Constructing multi-target controlled phase gate in circuit QED and its applications

Jin‐Xuan Han, Jin‐Lei Wu, Yan Wang +3 more

We present a one-step scheme in circuit quantum electrodynamics (QED) to realize multi-target controlled phase gates by using one microwave cavity that is coupled capacitively to a superconducting flux qutrit which plays the control role and simultaneously controls n target qutrits embedded in the microwave cavity. A strong classical field is imposed on the control qutrit so as to yield two dressed states, one of which is coded as a logical state. The controlled phase gates can be employed to achieve the creation of entangled states deterministically without any measurement, including the Bell state, the GHZ state, and the cluster state. Numerical simulations demonstrate that the high-fidelity creation of the entangled state is feasible with the constructed controlled phase gate under the present circuit QED technology.We present a one-step scheme in circuit quantum electrodynamics (QED) to realize multi-target controlled phase gates by using one microwave cavity that is coupled capacitively to a superconducting flux qutrit which plays the control role and simultaneously controls n target qutrits embedded in the microwave cavity. A strong classical field is imposed on the control qutrit so as to yield two dressed states, one of which is coded as a logical state. The controlled phase gates can be employed to achieve the creation of entangled states deterministically without any measurement, including the Bell state, the GHZ state, and the cluster state. Numerical simulations demonstrate that the high-fidelity creation of the entangled state is feasible with the constructed controlled phase gate under the present circuit QED technology.

Europhysics Letters (EPL)Oct 10, 20197 citations

99.9\%

for all-microwave controlled-phase operations with gate times in the range

50-120\,\mathrm{ns}

. These two-qubit gates can operate over a large drive-frequency bandwidth and in a broad range of circuit parameters, thereby improving extensibility. We address the frequency allocation problem for this architecture using perturbation theory, demonstrating that qubit, coupler and drive frequencies can be chosen such that undesired static and driven interactions remain bounded in a multi-qubit device. Our numerical methods are useful for describing the time-evolution of driven systems in the adiabatic limit, and are applicable to a wide variety of circuit-QED setups.