Enhancement of microwave squeezing via parametric down-conversion in a superconducting quantum circuit

Han, Kong; Wang, Yimin; Zhang, Guo-Qiang

doi:10.1364/oe.423373

Cited by 4 publications

(1 citation statement)

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“…We describe a semi-autonomous QEC protocol based on the unconditional periodic application of an optimized recovery operation, and we detail a simple procedure to determine the optimal recovery operation for given displacement and squeezing parameters. In this way, we show that the SC code significantly outperforms the 2-cat code in its resilience to single photon-loss errors, already at experimentally accessible values of the squeezing parameters [19,61,[65][66][67][68], while simultaneously improving the resilience to dephasing errors.…”

Section: Introductionmentioning

confidence: 70%

Quantum error correction using squeezed Schrödinger cat states

Schlegel,

Minganti,

Savona

2022

Preprint

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Bosonic quantum codes redundantly encode quantum information in the states of a quantum harmonic oscillator, making it possible to detect and correct errors. Schrödinger cat codes -based on the superposition of two coherent states with opposite displacements -can correct phase-flip errors induced by dephasing, but they are vulnerable to bit-flip errors induced by photon loss. Here, we develop a bosonic quantum code relying on squeezed cat states, i.e. cat states made of a linear superposition of displaced-squeezed states. Squeezed cat states allow to partially correct errors caused by photon loss, while at the same time improving the protection against dephasing. We present a comprehensive analysis of the squeezed cat code, including protocols for code generation and elementary quantum gates. We characterize the effect of both photon loss and dephasing and develop an optimal recovery protocol that is suitable to be implemented on currently available quantum hardware. We show that with moderate squeezing, and using typical parameters of stateof-the-art quantum hardware platforms, the squeezed cat code has a resilience to photon-loss errors that significantly outperforms that of the conventional cat code.

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Section: Introductionmentioning

confidence: 70%

Quantum error correction using squeezed Schrödinger cat states

Schlegel,

Minganti,

Savona

2022

Preprint

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Controllable coupling between fundamental modes in an asymmetric superconducting coplanar waveguide resonator

Mutsenik,

Sultanov,

Linzen

et al. 2024

Applied Physics Letters

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Controllable coupling between the odd and even fundamental modes of an asymmetric half-wavelength superconducting coplanar waveguide resonator is demonstrated. The resonant frequency of the even mode Ωe could be tuned by an external magnetic field, while the resonant frequency of the odd mode Ωo is field independent. To realize the tunability of Ωe, the central conductor of the NbN-based resonator was galvanically coupled to an array of Al-based rf-SQUIDs (radio frequency superconducting quantum interferometer device). These rf-SQUIDs are placed in only one resonator gap, ensuring its strong asymmetry. By adjusting the appropriate external magnetic flux Φ, equal frequencies of both modes were obtained. At this resonant point Ωo(Φ)=Ωe(Φ) an avoided level crossing of the eigenfrequencies was observed, demonstrating the coupling between the odd and even fundamental modes.

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