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Quantum dynamics and leakage of the superconducting flux qubit

Ezequiel N. Pozzo, Daniel Domı́nguez

Bulletin of the American Physical SocietyMar 16, 20060 citations

Leakage and Paralysis in Ancilla-assisted Qubit Measurement: Consequences for Topological Error Correction in Superconducting Architectures

Joydip Ghosh, Austin G. Fowler, John M. Martinis +1 more

Abstract : Although topological error-correcting codes offer a promising paradigm for fault- tolerant quantum computation, their robustness in the presence of leakage to non- computational states is unclear. Here we explore the signature and consequences of leakage errors on ancilla-assisted Pauli operator measurement in superconducting devices. We consider a realistic coupled-qutrit model and simulate the repeated measurement of a single sigma z operator. Typically, a data-qubit leakage event manifests itself by producing a noisy ancilla qubit that randomly reads /0/ or /1/ from cycle to cycle. Although the measurement operation is compromised, the presence of the leakage event is apparent and detectable. However, there is also the possibility of a less typical but more dangerous type of leakage event, where the ancilla becomes paralyzed rendering it oblivious to data-qubit errors for many consecutive measurement cycles and compromising the fault-tolerance. Certain dynamical phases associated with the entangling gate determine which type of leakage event will occur in practice. Leakage errors occur in most qubit realizations and our model and results are relevant for many stabilizer-based error correction protocols.Abstract : Although topological error-correcting codes offer a promising paradigm for fault- tolerant quantum computation, their robustness in the presence of leakage to non- computational states is unclear. Here we explore the signature and consequences of leakage errors on ancilla-assisted Pauli operator measurement in superconducting devices. We consider a realistic coupled-qutrit model and simulate the repeated measurement of a single sigma z operator. Typically, a data-qubit leakage event manifests itself by producing a noisy ancilla qubit that randomly reads /0/ or /1/ from cycle to cycle. Although the measurement operation is compromised, the presence of the leakage event is apparent and detectable. However, there is also the possibility of a less typical but more dangerous type of leakage event, where the ancilla becomes paralyzed rendering it oblivious to data-qubit errors for many consecutive measurement cycles and compromising the fault-tolerance. Certain dynamical phases associated with the entangling gate determine which type of leakage event will occur in practice. Leakage errors occur in most qubit realizations and our model and results are relevant for many stabilizer-based error correction protocols.

Jun 4, 20131 citation

Leakage and fidelity of real qubits

Rosario Fazio, G. Massimo Palma, Emilio Sciacca +1 more

Physica B Condensed MatterJul 1, 20000 citations

Dynamic Qubit Coupling

ScienceMay 3, 20070 citations

Quantum sensing in the presence of pulse errors and qubit leakage

David M. Lancaster, Muhammad Ali Shahbaz, Hamed Goli Yousefabad +3 more

Using both simulation and experiment, we investigate the robustness of dynamical decoupling sequences to pulse errors: rotation errors and detuning errors. Whereas prior work examined the effect of errors on coherence times, here we show that quantum sensing can be affected by pulse errors in dramatically different ways than coherence times alone. We also explore the effects of qubit leakage: off-resonant coupling to other quantum levels. We find order-of-magnitude differences between commonly used dynamical decoupling sequences in both their sensitivity to pulse errors and leakage.Using both simulation and experiment, we investigate the robustness of dynamical decoupling sequences to pulse errors: rotation errors and detuning errors. Whereas prior work examined the effect of errors on coherence times, here we show that quantum sensing can be affected by pulse errors in dramatically different ways than coherence times alone. We also explore the effects of qubit leakage: off-resonant coupling to other quantum levels. We find order-of-magnitude differences between commonly used dynamical decoupling sequences in both their sensitivity to pulse errors and leakage.

arXiv:2509.09874Physical Review ResearchAug 18, 20260 citations

Entropy Dynamics in the System of Interacting Qubits

N. S. Kirsanov, A. V. Lebedev, M. V. Suslov +3 more

arXiv:1804.06873Journal of Russian Laser ResearchMar 1, 201810 citations

Aspects of Qubit Dynamics in the Presence of Leakage

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