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Fundamental Limits to Cat Code Qubits from Chaos-Assisted Tunneling
Lionel E Martínez1,2, Ignacio García-Mata3, Diego A Wisniacki1
1Universidad de Buenos Aires, Departamento de Física "J.J. Giambiagi" and IFIBA, FCEyN, 1428 Buenos Aires, Argentina.
Physical Review Letters
|April 11, 2026
Summary
Chaos-assisted tunneling (CAT) limits the protection of Kerr-cat qubits. This study reveals that increasing nonlinearities lead to chaotic states that mediate tunneling, fundamentally bounding qubit coherence.
Area of Science:
- Quantum computing
- Superconducting qubits
- Quantum information science
Background:
- Kerr-cat qubits offer long lifetimes due to suppressed tunneling between degenerate cat states.
- Dynamically protected qubits are crucial for advancing quantum computation.
Purpose of the Study:
- To investigate the impact of chaos-assisted tunneling (CAT) on the coherence of Kerr-cat qubits.
- To determine if chaotic dynamics impose a fundamental limit on qubit protection.
Main Methods:
- Floquet analysis to study qubit dynamics under increasing nonlinearities.
- Full quantum simulations to compute tunneling rates.
- Semiclassical WKB theory for comparison with simulations.
Main Results:
- Chaos-assisted tunneling (CAT) was observed in Kerr-cat qubits for the first time.
- Increasing nonlinearities lead to chaotic states that mediate tunneling.
- Tunneling rates show large quasienergy splittings directly linked to chaos.
Conclusions:
- Chaos-assisted tunneling (CAT) imposes an intrinsic limit on the protection of Kerr-cat qubits.
- Dynamically protected superconducting qubits have a fundamental coherence bound set by chaos.
- Understanding CAT is essential for designing more robust quantum computing architectures.
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