Transmon qubit readout fidelity at the threshold for quantum error correction without a quantum-limited amplifier

• URL: http://arxiv.org/abs/2208.05879v1
• Date: Thu, 11 Aug 2022 15:29:38 GMT
• Title: Transmon qubit readout fidelity at the threshold for quantum error correction without a quantum-limited amplifier
• Authors: Liangyu Chen, Hang-Xi Li, Yong Lu, Christopher W. Warren, Christian J. Kri\v{z}an, Sandoko Kosen, Marcus Rommel, Shahnawaz Ahmed, Amr Osman, Janka Bizn\'arov\'a, Anita Fadavi Roudsari, Benjamin Lienhard, Marco Caputo, Kestutis Grigoras, Leif Gr\"onberg, Joonas Govenius, Anton Frisk Kockum, Per Delsing, Jonas Bylander, Giovanna Tancredi
• Abstract summary: High-fidelity and rapid readout of a qubit state is key to quantum computing and communication. We present a readout scheme for superconducting qubits that combines two microwave techniques. We demonstrate 99.5% assignment fidelity for two-state readout and 96.9% for three-state readout.
• Score: 1.8412219563671723
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: High-fidelity and rapid readout of a qubit state is key to quantum computing and communication, and it is a prerequisite for quantum error correction. We present a readout scheme for superconducting qubits that combines two microwave techniques: applying a shelving technique to the qubit that effectively increases the energy-relaxation time, and a two-tone excitation of the readout resonator to distinguish among qubit populations in higher energy levels. Using a machine-learning algorithm to post-process the two-tone measurement results further improves the qubit-state assignment fidelity. We perform single-shot frequency-multiplexed qubit readout, with a 140ns readout time, and demonstrate 99.5% assignment fidelity for two-state readout and 96.9% for three-state readout - without using a quantum-limited amplifier.

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