High-frequency readout free from transmon multi-excitation resonances

• URL: http://arxiv.org/abs/2501.09161v1
• Date: Wed, 15 Jan 2025 21:27:00 GMT
• Title: High-frequency readout free from transmon multi-excitation resonances
• Authors: Pavel D. Kurilovich, Thomas Connolly, Charlotte G. L. Bøttcher, Daniel K. Weiss, Sumeru Hazra, Vidul R. Joshi, Andy Z. Ding, Heekun Nho, Spencer Diamond, Vladislav D. Kurilovich, Wei Dai, Valla Fatemi, Luigi Frunzio, Leonid I. Glazman, Michel H. Devoret,
• Abstract summary: In superconducting quantum computers, measurement of the qubit state remains the lowest-fidelity operation. We find that strongly detuning the readout frequency from that of the transmon exponentially suppresses the strength of spurious multi-excitation resonances.
• Score: 1.6839391035385487
• License:
• Abstract: Quantum computation will rely on quantum error correction to counteract decoherence. Successfully implementing an error correction protocol requires the fidelity of qubit operations to be well-above error correction thresholds. In superconducting quantum computers, measurement of the qubit state remains the lowest-fidelity operation. For the transmon, a prototypical superconducting qubit, measurement is carried out by scattering a microwave tone off the qubit. Conventionally, the frequency of this tone is of the same order as the transmon frequency. The measurement fidelity in this approach is limited by multi-excitation resonances in the transmon spectrum which are activated at high readout power. These resonances excite the qubit outside of the computational basis, violating the desired quantum non-demolition character of the measurement. Here, we find that strongly detuning the readout frequency from that of the transmon exponentially suppresses the strength of spurious multi-excitation resonances. By increasing the readout frequency up to twelve times the transmon frequency, we achieve a quantum non-demolition measurement fidelity of 99.93% with a residual probability of leakage to non-computational states of only 0.02%.

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