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Scalable Quantum Integrated Circuits on Superconducting Two-Dimensional Electron Gas Platform
Published on: August 2, 2019
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Two-level systems in superconducting quantum devices due to trapped quasiparticles.
S E de Graaf1, L Faoro2,3, L B Ioffe3,4
1National Physical Laboratory, Hampton Road, Teddington TW11 0LW, UK. sdg@npl.co.uk.
Science Advances
|December 23, 2020
Summary
We discovered a new quantum decoherence mechanism caused by trapped quasiparticles (QPs) forming two-level system (TLS) defects. This QP-induced TLS impacts superconducting qubit coherence over extended periods, even with rare QP events.
Area of Science:
- Quantum Computing
- Condensed Matter Physics
- Materials Science
Background:
- Superconducting quantum circuits face decoherence from two-level system (TLS) defects and nonequilibrium quasiparticles (QPs).
- These factors cause qubit parameter fluctuations, relaxation, and dephasing, hindering large-scale implementation.
Purpose of the Study:
- To identify and characterize a novel decoherence mechanism in superconducting qubits.
- To investigate the role of trapped quasiparticles (QPs) in forming new types of two-level system (TLS) defects.
Main Methods:
- Utilized spectral, temporal, thermal, and magnetic field mapping of TLS-induced fluctuations.
- Analyzed frequency-tunable resonators to study TLS properties.
- Investigated the behavior of TLS at low temperatures (∼300 mK).
Main Results:
- Discovered a new TLS type originating from trapped QPs, inducing qubit relaxation.
- Identified a coherent subset of TLS with a low reconfiguration temperature (∼300 mK).
- Observed a nonuniform density of states for these QP-induced TLS.
Conclusions:
- QP-induced TLS, formed in shallow subgap states, represent a significant decoherence pathway.
- Even infrequent QP bursts can lead to long-term coherence degradation in superconducting qubits.
- Understanding this mechanism is crucial for advancing scalable quantum computing.
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