High speed flux sampling for tunable superconducting qubits with an embedded cryogenic transducer

Abstract

We develop a high speed on-chip flux measurement using a capacitively shunted SQUID as an embedded cryogenic transducer and apply this technique to the qualification of a near-term scalable printed circuit board (PCB) package for frequency tunable superconducting qubits. The transducer is a flux tunable LC resonator where applied flux changes the resonant frequency. We apply a microwave tone to probe this frequency and use a time-domain homodyne measurement to extract the reflected phase as a function of flux applied to the SQUID. The transducer response bandwidth is 2.6 GHz with a maximum gain of $1200^{\circ }/{\mathrm{\Phi }}_0$ allowing us to study the settling amplitude to better than 0.1%. We use this technique to characterize on-chip bias line routing and a variety of PCB based packages and demonstrate that step response settling can vary by orders of magnitude in both settling time and amplitude depending on if normal or superconducting materials are used. By plating copper PCBs in aluminum we measure a step response consistent with the packaging used for existing high-fidelity qubits.

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• Tutorial: Gate-based superconducting quantum computing
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• Rapid and Unconditional Parametric Reset Protocol for Tunable Superconducting Qubits
• Microwave Package Design for Superconducting Quantum Processors
• Reducing leakage of single-qubit gates for superconducting quantum processors using analytical control pulse envelopes
• Realization of Superadiabatic Two-qubit Gates Using Parametric Modulation in Superconducting Circuits
• Coupler-Assisted Controlled-Phase Gate with Enhanced Adiabaticity
• Realization of fast all-microwave CZ gates with a tunable coupler
• Fabrication of the impedance-matched Josephson parametric amplifier and the study of the gain profile
• Baseband control of superconducting qubits with shared microwave drives
• Hardware implementation of quantum stabilizers in superconducting circuits