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

Liangyu Chen (Corresponding Author), Hang Xi Li, Yong Lu, Christopher W. Warren, Christian J. Križan, Sandoko Kosen, Marcus Rommel, Shahnawaz Ahmed, Amr Osman, Janka Biznárová, Anita Fadavi Roudsari, Benjamin Lienhard, Marco Caputo, Kestutis Grigoras, Leif Grönberg, Joonas Govenius, Anton Frisk Kockum, Per Delsing, Jonas Bylander (Corresponding Author), Giovanna Tancredi (Corresponding Author)

Research output: Contribution to journalArticleScientificpeer-review

25 Citations (Scopus)

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 reduces the contribution of decay error during readout, 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 140 ns 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.

Original languageEnglish
Article number26
Number of pages7
JournalNPJ Quantum Information
Volume9
Issue number1
DOIs
Publication statusPublished - Mar 2023
MoE publication typeA1 Journal article-refereed

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