两类不同纠缠态下三方猫态的演示
Demonstration of tripartite cat states in two distinct classes of entanglement
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中文总结 AI 辅助
研究通过三个微波谐振器与辅助超导跨导量子比特耦合，实现两类宏观三方纠缠猫态，利用跨导量子比特能级生成态并重构，获不同保真度，验证不同纠缠类，为宏观多体纠缠和容错量子信息处理研究提供测试平台。
中文摘要 AI 辅助
纠缠是量子力学的基石，也是量子计算、通信和计量学的重要资源。虽然两体纠缠已被广泛研究，但在宏观连续变量领域，真正的多体纠缠态仍难以实现。本文通过与辅助超导跨导量子比特耦合的三个微波谐振器，实验实现了具有根本不同性质的两类宏观三方纠缠猫态，即GHZ猫态和W猫态。利用跨导量子比特的三个能级在单个硬件中生成这些态，并采用高效的子空间层析成像协议进行态重构。得到的GHZ猫态和W猫态保真度分别为0.83±0.02和0.70±0.02，证明了三个振子之间存在真正的多体纠缠。通过实验证明W猫态存在两体纠缠而GHZ猫态不存在，进一步验证了不同的纠缠类。我们按需生成和表征不等价类三方连续变量纠缠的技术，为宏观多体纠缠和多体玻色子码的容错量子信息处理的未来研究提供了有价值的测试平台。
英文摘要
Entanglement is a cornerstone of quantum mechanics and an essential resource for quantum computation, communication, and metrology. While bipartite entanglement is extensively studied, genuine multipartite entangled states remain largely inaccessible in the macroscopic continuous-variable domain. Here, we experimentally realize macroscopic tripartite entangled cat states of the two distinct classes with fundamentally inequivalent properties, namely GHZ-cat and W-cat states, encoded across three microwave resonators coupled to an ancillary superconducting transmon. We develop one-to-all conditional controls on the three oscillators by fully utilizing three energy levels of the transmon to generate these states in a single piece of hardware and employ an efficient subspace tomography protocol for state reconstruction. We obtain GHZ-cat and W-cat states with fidelities $0.83\pm0.02$ and $0.70\pm0.02$, respectively, certifying genuine multipartite entanglement among the three oscillators. We further validate the distinct entanglement classes by experimentally demonstrating that pairwise entanglement is present in the W-cat state but absent in the GHZ-cat state. Our technique for the on-demand generation and characterization of inequivalent classes of tripartite continuous-variable entanglement provides a valuable testbed for future studies of macroscopic many-body entanglement and fault-tolerant quantum information processing with multipartite bosonic codes.
