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AI summary · arXiv: 2611.04868v1 · quant-ph

Autonomous cooling of Kerr-cat qubits to minutes-long bit-flip times

Sergey Hazanov, Mikhail Svintsov, Uri Goldblatt, Barkay Guttel, Fabien Lafont, Serge Rosenblum
Original paper Submitted to arXiv on 03 Nov. 2026 32 pages, 5 main figures, 14 supplementary figures License: not stated (all rights reserved) Also in: fr

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The essentials

The authors demonstrate autonomous cooling in Kerr-cat qubits, extending bit-flip times to 450 seconds while retaining fast control and readout.

Based on the abstract only: check the details in the original paper.

Question

Can the nonlinear interaction that confines Kerr-cat states also cool excitations that cause interwell switching and limit bit-flip protection? The paper examines whether this can extend bit-flip times without sacrificing fast control.

Method

The authors use a lossy readout mode resonant with an intra-well transition to remove excitations from the qubit, and establish the cooling mechanism through spectroscopy and relaxation measurements. They measure bit-flip-time scaling with photon number, phase-flip rates, Z-gate performance, and single-shot readout.

Findings

  • Result Resonant coupling of an intra-well transition to a lossy readout mode transfers excitations out of the qubit and dissipates them.
    See the passage in the paper
    When an intra-well transition becomes resonant with a lossy readout mode, excitations are transferred out of the qubit and dissipated, as established by spectroscopy and relaxation measurements.
  • Result Bit-flip times show the predicted exponential scaling with photon number and reach 450 seconds.
    See the passage in the paper
    We observe the predicted exponential scaling of Kerr-cat bit-flip times with photon number, reaching 450 s, over five orders of magnitude beyond previous demonstrations.
  • Result At operating points with seconds-long bit-flip times, phase-flip rates are consistent with intrinsic photon loss.
    See the passage in the paper
    Phase-flip rates remain consistent with intrinsic photon loss at operating points with seconds-long bit-flip times.
  • Result Fast Z gates do not measurably degrade bit-flip protection, and single-shot readout has a bit-flip probability below 10^-6 per measurement.
    See the passage in the paper
    We further demonstrate fast Z gates without measurable degradation of bit-flip protection and single-shot readout with a bit-flip probability below $10^{-6}$ per measurement.
  • Authors’ interpretation The authors argue that autonomous cooling enables long bit-flip protection without extra cooling drives or circuit elements.
    See the passage in the paper
    Autonomous cooling thus brings minutes-long bit-flip protection to Kerr-cat qubits while retaining fast coherent control, without additional cooling drives or circuit elements.

Limitations

  • The reported evidence is specific to the demonstrated Kerr-cat qubit system and does not establish performance in other architectures.

Why it matters

The authors argue that autonomous cooling can extend Kerr-cat bit-flip protection to minutes while preserving fast coherent control. Their approach does so without additional cooling drives or circuit elements.

Written by AI from the paper. Passages are checked word for word against the text we analysed; the rest may contain errors.

AI-generated keywords: Kerr-cat qubits autonomous cooling bit-flip protection phase-flip errors quantum error correction

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  • Comprehensive Summary
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  • Blog article
  • Original abstract
The paper asks whether Kerr-cat qubits can retain strong bit-flip suppression while avoiding the excitation-driven switching that has limited their bit-flip times to milliseconds. A Kerr-cat qubit encodes information in two opposite coherent states of a superconducting oscillator. Increasing the photon number can suppress bit flips exponentially, while phase flips are expected to increase only linearly. However, excitations within either state can trigger transitions between the two states, undermining this protection. The authors investigate whether the nonlinear interaction that creates the Kerr-cat’s double-well confinement can also remove these excitations. Their proposed mechanism is autonomous cooling: an intra-well transition is tuned into resonance with a lossy readout mode. Excitations can then transfer from the qubit to the mode and dissipate, without an additional cooling drive or circuit elements. The abstract reports spectroscopy and relaxation measurements as evidence that this transfer occurs. The paper also examines how cooling affects bit-flip protection, phase-flip rates, fast Z gates, and readout. Its central result is a measured exponential increase in bit-flip times with photon number, consistent with Kerr-cat protection. The longest reported bit-flip time is 450 seconds—about seven and a half minutes and more than five orders of magnitude longer than in previous demonstrations. At operating points where bit-flip times reach seconds, measured phase-flip rates remain consistent with those expected from intrinsic photon loss. This is important because stronger bit-flip protection would be less useful if it introduced a substantial additional source of phase errors. The authors also report fast Z gates without measurable degradation of bit-flip protection, along with single-shot readout yielding a bit-flip probability below one in a million per measurement. They conclude that cooling through the Kerr nonlinearity can extend bit-flip protection to minutes while preserving fast coherent control, without extra cooling hardware or drives. These results support the potential of Kerr-cat qubits for hardware-efficient quantum error correction, where a strong bias toward one type of error can reduce the resources required to correct it. The available source contains only the title, authors, and abstract; the full text is unavailable under the stated license. Therefore, details needed for a fuller assessment—including device parameters, experimental protocols, uncertainties, the precise range of the observed exponential scaling, and comparisons across operating conditions—cannot be established here. The abstract also does not provide enough information to assess the approach’s robustness beyond the demonstrated settings or its scalability to larger systems. These limitations qualify the scope of this summary but do not negate the reported measurements.
Created on 10 Nov. 2026

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Weekly letter Presented in "Quantum physics this week" of 9 November 2026. Quantum physics this week: Protecting fragile states, exposing fragile advantages
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