超导电路中的条件压缩门
Conditional-squeezing gate in superconducting circuits
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中文总结 AI 辅助
本文提出超导电路中基于重聚焦技术的条件压缩门，用于将量子比特态编码为压缩态叠加，实现高保真度（>0.99）的可检错编码，并推广至高阶旋转对称玻色子编码。
中文摘要 AI 辅助
我们提出了一种条件压缩门的实现方案，该门沿着由色散耦合量子比特状态决定的方向压缩一个以SQUID为终端的谐振腔模式。此门推广了受控压缩门[Phys. Rev. A 111, 042606 (2025)]，并依赖于一种重聚焦技术来抑制在操作所需的状态依赖参数共振期间，哈密顿量中缓慢变化的含时项所引起的不利效应。作为应用，我们利用该门将任意量子比特态编码为谐振腔单模和双模压缩态的叠加。这些非高斯态能够通过宇称测量实现可检错编码。我们表明，重聚焦显著提高了编码保真度，而该保真度最终受限于实际实现中的克尔非线性和耗散。对于实验上乐观的非线性和衰减率取值，我们对任意输入量子比特态获得的编码保真度高于0.99。我们的结果为将该方案扩展到使用控制量子比特（qudit）生成高阶压缩态叠加（一类旋转对称玻色子编码）提供了途径。
英文摘要
We present an implementation of a conditional-squeezing gate that squeezes a SQUID-terminated resonator mode along a direction determined by the state of a dispersively coupled qubit. This gate generalizes the controlled-squeezing gate [Phys. Rev. A \textbf{111}, 042606 (2025)], and relies on a refocusing technique to suppress unwanted effects arising from slowly varying time-dependent terms in the Hamiltonian during the state-dependent parametric resonance required for the operation. As an application, we use the gate to encode an arbitrary qubit state into superpositions of single- and two-mode squeezed states of the resonator. These non-Gaussian states enable error-detectable encoding through parity measurements. We show that refocusing substantially improves the encoding fidelity, which is ultimately limited by Kerr nonlinearities and dissipation in realistic implementations. For experimentally optimistic values of the nonlinearities and decay rates, we obtain encoding fidelities above 0.99 for arbitrary input qubit states. Our results provide a route toward extending this scheme to the generation of higher-order superpositions of squeezed states (a class of rotation-symmetric bosonic codes) using a control qudit.
发表机构
- Universidad de Buenos Aires（布宜诺斯艾利斯大学）
- CONICET – Universidad de Buenos Aires（阿根廷国家科学研究委员会-布宜诺斯艾利斯大学）
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