Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Conference on Precision Electromagnetic Measurements

Superconducting qubit coherence metrics for device engineering

Corey Rae McRae, Jorge Ramirez, Manognya Acharya, John R. Pitten, T. Lindström, D. A. Bennett

Published Jul 8, 2024• 0 citations
Publisher

Abstract

Superconducting qubit coherence has a precision problem. Relaxation time T1and decoherence time T2are by far the most common benchmarks of single qubit performance in superconducting quantum circuits, and are heavily relied upon for engineering next-generation devices. However, these metrics have strong environmental sensitivities and are temporally unstable, and thus alone are not robust metrics for describing individual qubits and comparing them against one another.In this tutorial, the measurement and interpretation of superconducting qubit coherence metrics is detailed, and useful qubit metrics are outlined that consider current knowledge of T1and T2variation sources.

DOI
10.1109/cpem61406.2024.10646055

Related papers

Reproducible coherence characterization of superconducting quantum devices

Corey Rae McRae, Gregory M. Stiehl, Haozhi Wang +5 more

As the field of superconducting quantum computing approaches maturity, optimization of single-device performance is proving to be a promising avenue toward large-scale quantum computers. However, this optimization is possible only if performance metrics can be accurately compared among measurements, devices, and laboratories. Currently, such comparisons are inaccurate or impossible due to understudied errors from a plethora of sources. In this Perspective, we outline the current state of error analysis for qubits and resonators in superconducting quantum circuits and discuss what future investigations are required before superconducting quantum device optimization can be realized.

arXiv:2106.09864•Applied Physics Letters•Sep 6, 2021•13 citations

Quantum metrology based on superconducting qubits

Anton Kolosvetov, Nikolay Gusarov, Vladimir Slepnev +4 more

Quantum metrology based on superconducting qubits offers unprecedented precision in measuring fundamental physical quantities, particularly magnetic fields. In this study, we develop a modified quantum phase estimation algorithm utilizing superconducting qubits, enhanced by optimized initial state preparation, significantly improving measurement sensitivity and reducing estimation times compared to conventional techniques. To ensure practical applicability and robustness, we incorporate advanced noise modeling, including intrinsic decoherence effects such as flux-induced noise and Purcell losses. Through detailed analytical modeling and numerical simulations, we systematically evaluate sensitivity and practical implementation constraints across various superconducting qubit architectures—transmon, fluxonium, conventional flux, and C-shunt flux qubits. Our approach quantifies the critical trade-offs between coherence, measurement dynamics, and sensitivity, identifying optimal operational regimes for high-performance quantum sensing. We introduce custom circuit simulation methods enabling the analysis and optimization of arbitrary superconducting quantum devices. Our findings provide a framework for advancing quantum-enhanced magnetometry and promise to facilitate next-generation quantum sensors for fundamental physics research, gravitational field measurements, and quantum-assisted searches for dark matter candidates.

npj Quantum Information•Jun 4, 2026•1 citation

Open quantum system approaches to superconducting qubits

Hamid Reza Naeij

Abstract Superconducting qubits are currently a leading platform for developing a scalable quantum computer. However, random and uncontrollable noises from the environment during the design and measurement of qubits lead to limitations in qubit coherence time and gate fidelity, which is a major challenge in current state of the art for superconducting quantum computing. To advance superconducting qubits technologies, it is essential to understand and mitigate environmentally-induced errors. This requires modeling superconducting qubits as open quantum systems coupled to their surroundings. The present study aims to provide useful open quantum system approaches to analyze and quantify the interaction between superconducting qubits and their environments. We provide an accessible introduction to open quantum system formalism for newcomers to the field. For experts, we discuss recently developed methods for analyzing superconducting qubit dynamics under realistic noises. We outline how these techniques provide quantitative insights into decoherence mechanisms and how they can guide design improvements to enhance qubit coherence time. This self-contained review of open quantum system approaches can be used to model, understand, and improve superconducting qubit performance in the presence of unavoidable environmental noises.

arXiv:2402.19241•Quantum Information Processing•Jul 11, 2025•2 citations

Decoherence benchmarking of superconducting qubits

Jonathan Burnett, Andreas Bengtsson, Marco Scigliuzzo +4 more

Abstract We benchmark the decoherence of superconducting transmon qubits to examine the temporal stability of energy relaxation, dephasing, and qubit transition frequency. By collecting statistics during measurements spanning multiple days, we find the mean parameters $$\overline {T_1}$$ T 1 ¯ = 49 μs and $$\overline {T_2^ \ast }$$ T 2 * ¯ = 95 μs; however, both of these quantities fluctuate, explaining the need for frequent re-calibration in qubit setups. Our main finding is that fluctuations in qubit relaxation are local to the qubit and are caused by instabilities of near-resonant two-level-systems (TLS). Through statistical analysis, we determine sub-millihertz switching rates of these TLS and observe the coherent coupling between an individual TLS and a transmon qubit. Finally, we find evidence that the qubit’s frequency stability produces a 0.8 ms limit on the pure dephasing which we also observe. These findings raise the need for performing qubit metrology to examine the reproducibility of qubit parameters, where these fluctuations could affect qubit gate fidelity.

arXiv:1901.04417•npj Quantum Information•Jun 26, 2019•381 citations

Real-Time Correlation of Relaxation, Dephasing, and Two-level System Dynamics in Transmon Qubits

Ambrose Yang, Alexander M. Young, Paal H. Prestegaard +13 more

Materials improvements in transmon qubits have yielded remarkable advances in qubit lifetimes (T1)and coherence times (T2). However, state-of-the-art superconducting qubits experience temporal fluctuations in their performance, which limit gate fidelities and quantum processor performance. We observe correlated increases in qubit relaxation and dephasing rates that last for minutes to hours, which we call T1 and T2 excursions. Using interleaved lifetime and coherence time measurements, noise spectroscopy, and two-level-system (TLS) spectroscopy, we find that these excursions are caused by single or few strongly-coupled TLS defects that spectrally diffuse into resonance with the qubit frequency. Our measurement protocol provides a powerful tool for understanding the noise sources that cause temporal fluctuations in superconducting qubit performance.

quant-pharXiv:2610.34485•Oct 27, 2026•0 citations

Superconducting Quantum Bits of Information—Coherence and Design Improvements

Jonas Bylander

This article reviews recent progress in superconducting quantum bits, including major improvements in design and coherence times. It first provides an overview of the basics of modern superconducting qubit devices and their architectures before turning to single-qubit Hamiltonians and reference frames. It then examines how decoherence originates with noise and shows how to characterize and mitigate this noise using magnetic-resonance-type pulse sequences. It also describes the first-generation superconducting qubits and the now-dominant circuit-quantum electrodynamics architecture in which qubits are coupled to microwave resonators. Finally, it considers several improved designs of superconducting qubits in which coherence times have been significantly improved by minimizing the sensitivity to fluctuating impurities and the coupling to external modes.

Oxford University Press eBooks•Jul 6, 2017•2 citations
Superconducting qubit coherence has a precision problem. Relaxation time T1and decoherence time T2are by far the most common benchmarks of single qubit performance in superconducting quantum circuits, and are heavily relied upon for engineering next-generation devices. However, these metrics have strong environmental sensitivities and are temporally unstable, and thus alone are not robust metrics for describing individual qubits and comparing them against one another.In this tutorial, the measurement and interpretation of superconducting qubit coherence metrics is detailed, and useful qubit metrics are outlined that consider current knowledge of T1and T2variation sources.
As the field of superconducting quantum computing approaches maturity, optimization of single-device performance is proving to be a promising avenue toward large-scale quantum computers. However, this optimization is possible only if performance metrics can be accurately compared among measurements, devices, and laboratories. Currently, such comparisons are inaccurate or impossible due to understudied errors from a plethora of sources. In this Perspective, we outline the current state of error analysis for qubits and resonators in superconducting quantum circuits and discuss what future investigations are required before superconducting quantum device optimization can be realized.
Quantum metrology based on superconducting qubits offers unprecedented precision in measuring fundamental physical quantities, particularly magnetic fields. In this study, we develop a modified quantum phase estimation algorithm utilizing superconducting qubits, enhanced by optimized initial state preparation, significantly improving measurement sensitivity and reducing estimation times compared to conventional techniques. To ensure practical applicability and robustness, we incorporate advanced noise modeling, including intrinsic decoherence effects such as flux-induced noise and Purcell losses. Through detailed analytical modeling and numerical simulations, we systematically evaluate sensitivity and practical implementation constraints across various superconducting qubit architectures—transmon, fluxonium, conventional flux, and C-shunt flux qubits. Our approach quantifies the critical trade-offs between coherence, measurement dynamics, and sensitivity, identifying optimal operational regimes for high-performance quantum sensing. We introduce custom circuit simulation methods enabling the analysis and optimization of arbitrary superconducting quantum devices. Our findings provide a framework for advancing quantum-enhanced magnetometry and promise to facilitate next-generation quantum sensors for fundamental physics research, gravitational field measurements, and quantum-assisted searches for dark matter candidates.
Abstract Superconducting qubits are currently a leading platform for developing a scalable quantum computer. However, random and uncontrollable noises from the environment during the design and measurement of qubits lead to limitations in qubit coherence time and gate fidelity, which is a major challenge in current state of the art for superconducting quantum computing. To advance superconducting qubits technologies, it is essential to understand and mitigate environmentally-induced errors. This requires modeling superconducting qubits as open quantum systems coupled to their surroundings. The present study aims to provide useful open quantum system approaches to analyze and quantify the interaction between superconducting qubits and their environments. We provide an accessible introduction to open quantum system formalism for newcomers to the field. For experts, we discuss recently developed methods for analyzing superconducting qubit dynamics under realistic noises. We outline how these techniques provide quantitative insights into decoherence mechanisms and how they can guide design improvements to enhance qubit coherence time. This self-contained review of open quantum system approaches can be used to model, understand, and improve superconducting qubit performance in the presence of unavoidable environmental noises.
Abstract We benchmark the decoherence of superconducting transmon qubits to examine the temporal stability of energy relaxation, dephasing, and qubit transition frequency. By collecting statistics during measurements spanning multiple days, we find the mean parameters T1‾\overline {T_1}T1​​ T 1 ¯ = 49 μs and T2∗‾\overline {T_2^ \ast }T2∗​​ T 2 * ¯ = 95 μs; however, both of these quantities fluctuate, explaining the need for frequent re-calibration in qubit setups. Our main finding is that fluctuations in qubit relaxation are local to the qubit and are caused by instabilities of near-resonant two-level-systems (TLS). Through statistical analysis, we determine sub-millihertz switching rates of these TLS and observe the coherent coupling between an individual TLS and a transmon qubit. Finally, we find evidence that the qubit’s frequency stability produces a 0.8 ms limit on the pure dephasing which we also observe. These findings raise the need for performing qubit metrology to examine the reproducibility of qubit parameters, where these fluctuations could affect qubit gate fidelity.
Materials improvements in transmon qubits have yielded remarkable advances in qubit lifetimes (T1)and coherence times (T2). However, state-of-the-art superconducting qubits experience temporal fluctuations in their performance, which limit gate fidelities and quantum processor performance. We observe correlated increases in qubit relaxation and dephasing rates that last for minutes to hours, which we call T1 and T2 excursions. Using interleaved lifetime and coherence time measurements, noise spectroscopy, and two-level-system (TLS) spectroscopy, we find that these excursions are caused by single or few strongly-coupled TLS defects that spectrally diffuse into resonance with the qubit frequency. Our measurement protocol provides a powerful tool for understanding the noise sources that cause temporal fluctuations in superconducting qubit performance.
This article reviews recent progress in superconducting quantum bits, including major improvements in design and coherence times. It first provides an overview of the basics of modern superconducting qubit devices and their architectures before turning to single-qubit Hamiltonians and reference frames. It then examines how decoherence originates with noise and shows how to characterize and mitigate this noise using magnetic-resonance-type pulse sequences. It also describes the first-generation superconducting qubits and the now-dominant circuit-quantum electrodynamics architecture in which qubits are coupled to microwave resonators. Finally, it considers several improved designs of superconducting qubits in which coherence times have been significantly improved by minimizing the sensitivity to fluctuating impurities and the coupling to external modes.