Benchmarking the readout of a superconducting qubit for repeated measurements

Abstract

Readout of superconducting qubits faces a trade-off between measurement speed and unwanted back-action on the qubit caused by the readout drive, such as $T_1$ degradation and leakage out of the computational subspace. The readout is typically benchmarked by integrating the readout signal and choosing a binary threshold to extract the "readout fidelity". We show that readout fidelity may significantly overlook readout-induced leakage errors. Such errors are detrimental for applications that rely on continuously repeated measurements, e.g., quantum error correction. We introduce a method to measure the readout-induced leakage rate by repeatedly executing a composite operation - a readout preceded by a randomized qubit-flip. We apply this technique to characterize the readout of a superconducting qubit, optimized for fidelity across four different readout durations. Our technique highlights the importance of an independent leakage characterization by showing that the leakage rates vary from $0.12\%$ to $7.76\%$ across these readouts even though the fidelity exceeds $99.5\%$ in all four cases.

References in corpus (20)

• Charge insensitive qubit design derived from the Cooper pair box
• Suppressing quantum errors by scaling a surface code logical qubit
• Controlling the spontaneous emission of a superconducting transmon qubit
• Qubit-photon interactions in a cavity: Measurement induced dephasing and number splitting
• Real-time quantum error correction beyond break-even
• Beating the break-even point with a discrete-variable-encoded logical qubit
• Thermal and Residual Excited-State Population in a 3D Transmon Qubit
• Initialization by measurement of a two-qubit superconducting circuit
• Protocols for optimal readout of qubits using a continuous quantum nondemolition measurement
• Fast readout and reset of a superconducting qubit coupled to a resonator with an intrinsic Purcell filter
• A superconducting qubit with Purcell protection and tunable coupling
• Dynamics of Transmon Ionization
• Overcoming leakage in scalable quantum error correction
• Transmon qubit readout fidelity at the threshold for quantum error correction without a quantum-limited amplifier
• Measurement-Induced State Transitions in a Superconducting Qubit: Within the Rotating Wave Approximation
• Measurement-Induced Transmon Ionization
• Enhancing Dispersive Readout of Superconducting Qubits Through Dynamic Control of the Dispersive Shift: Experiment and Theory
• Photon-noise-tolerant dispersive readout of a superconducting qubit using a nonlinear Purcell filter
• Low-pass filter with ultra-wide stopband for quantum computing applications
• Efficient decoupling of a non-linear qubit mode from its environment

Cited by in corpus (13)

• Fast multiplexed superconducting qubit readout with intrinsic Purcell filtering
• Enhanced Qubit Readout via Reinforcement Learning
• Characterization of drive-induced unwanted state transitions in superconducting circuits
• Balanced cross-Kerr coupling for superconducting qubit readout
• Wireless Josephson parametric amplifier above 20 GHz
• Above 99.9% Fidelity Single-Qubit Gates, Two-Qubit Gates, and Readout in a Single Superconducting Quantum Device
• Detector of microwave photon pairs based on a Josephson photomultiplier
• Mitigating Measurement Crosstalk via Pulse Shaping
• Feedforward suppression of readout-induced faults in quantum error correction
• Logical operations with a dynamical qubit in Floquet-Bacon-Shor code
• Review of Superconducting Qubit Devices and Their Large-Scale Integration
• Mitigating errors in state preparation and measurement with noncomputational states
• Mitigating state transition errors during readout with a synchronized flux pulse