Autoparametric resonance extending the bit-flip time of a cat qubit up to 0.3 s

Abstract

Cat qubits, for which logical $|0⟩$ and $|1⟩$ are coherent states $|\pm \alpha ⟩$ of a harmonic mode, offer a promising route towards quantum error correction. Using dissipation to our advantage so that photon pairs of the harmonic mode are exchanged with single photons of its environment, it is possible to stabilize the logical states and exponentially increase the bit-flip time of the cat qubit with the photon number $|\alpha {|}^2$. Large two-photon dissipation rate ${\kappa }_2$ ensures fast qubit manipulation and short error correction cycles, which are instrumental to correct the remaining phase-flip errors in a repetition code of cat qubits. Here we introduce and operate an autoparametric superconducting circuit that couples a mode containing the cat qubit to a lossy mode whose frequency is set at twice that of the cat mode. This passive coupling does not require a parametric pump and reaches a rate ${\kappa }_2/2\pi \approx 2\mathrm{MHz}$. With such a strong two-photon dissipation, bit-flip errors of the autoparametric cat qubit are prevented for a characteristic time up to 0.3~s with only a mild impact on phase-flip errors. Besides, we illustrate how the phase of a quantum superposition between $|\alpha ⟩$ and $|-\alpha ⟩$ can be arbitrarily changed by driving the harmonic mode while keeping the engineered dissipation active.

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• Harnessing two-photon dissipation for enhanced quantum measurement and control
• Multi-Purpose Architecture for Fast Reset and Protective Readout of Superconducting Qubits
• Hybrid cat-transmon architecture for scalable, hardware-efficient quantum error correction
• Preserving phase coherence and linearity in cat qubits with exponential bit-flip suppression
• Bit-flip errors in dissipative cat qubits: second-order perturbation theory
• Engineering the Nonlinearity of Bosonic Modes with a Multi-loop SQUID
• Theory of quasiparticle-induced errors in driven-dissipative Schrödinger cat qubits
• A cat qubit stabilization scheme using a voltage biased Josephson junction
• Non-perturbative switching rates in bistable open quantum systems: from driven Kerr oscillators to dissipative cat qubits
• Quantum teleportation of cat states with binary-outcome measurements