近日，美国加州理工学院的Manuel Endres及其研究团队取得一项新进展。经过不懈努力，他们提出针对光镊钟的通用量子操作和基于辅助量子位的读出方法。相关研究成果已于2024年10月9日在国际权威学术期刊《自然》上发表。

该研究团队展示了针对中性原子超窄光学跃迁的通用量子操作和基于辅助量子位的读出方法。研究人员在光镊钟平台上进行的演示，使得中性原子光钟能够采用基于电路的量子计量学方法。为此，研究人员通过里德伯相互作用和光学时钟量子位的动态连接，实现了平均保真度为99.62(3)%（针对对称输入态）的两量子位纠缠门，并将其与局部寻址相结合，以实现可通用编程的量子电路。

采用这种方法，他们生成了近优的纠缠探测态，即不同大小级联的Greenberger-Horne-Zeilinger（GHZ）态，并执行了双正交分量GHZ读出。他们还展示了通过为中性原子实施基于辅助量子位的量子逻辑光谱学，实现了快速相位检测的重复测量，以及对时钟量子位的非破坏性条件重置，同时使重复测量之间的死区时间最小化。

最后，他们将此扩展到多量子位奇偶校验和基于测量的、有预示的贝尔态制备。这项研究工作为中性原子的混合处理器-时钟设备奠定了基础，并更广泛地指出了量子处理器与量子传感器相结合的未来实际应用前景。

据悉，在量子计量学中，利用纠缠提高测量精度是一个长期追求的目标。然而，在噪声存在的情况下达到量子理论所允许的最佳灵敏度是一项重大挑战，这要求采用最优的探测态生成和读出策略。中性原子光学钟作为测量时间的领先系统，在纠缠生成方面已取得近期进展，但目前尚缺乏实现此类方案的控制能力。

附：英文原文

Title: Universal quantum operations and ancilla-based read-out for tweezer clocks

Author: Finkelstein, Ran, Tsai, Richard Bing-Shiun, Sun, Xiangkai, Scholl, Pascal, Direkci, Su, Gefen, Tuvia, Choi, Joonhee, Shaw, Adam L., Endres, Manuel

Issue&Volume: 2024-10-09

Abstract: Enhancing the precision of measurements by harnessing entanglement is a long-sought goal in quantum metrology. Yet attaining the best sensitivity allowed by quantum theory in the presence of noise is an outstanding challenge, requiring optimal probe-state generation and read-out strategies. Neutral-atom optical clocks, which are the leading systems for measuring time, have shown recent progress in terms of entanglement generation but at present lack the control capabilities for realizing such schemes. Here we show universal quantum operations and ancilla-based read-out for ultranarrow optical transitions of neutral atoms. Our demonstration in a tweezer clock platform enables a circuit-based approach to quantum metrology with neutral-atom optical clocks. To this end, we demonstrate two-qubit entangling gates with 99.62(3)% fidelity—averaged over symmetric input states—through Rydberg interactions and dynamical connectivity for optical clock qubits, which we combine with local addressing to implement universally programmable quantum circuits. Using this approach, we generate a near-optimal entangled probe state, a cascade of Greenberger–Horne–Zeilinger states of different sizes, and perform a dual-quadrature Greenberger–Horne–Zeilinger read-out. We also show repeated fast phase detection with non-destructive conditional reset of clock qubits and minimal dead time between repetitions by implementing ancilla-based quantum logic spectroscopy for neutral atoms. Finally, we extend this to multi-qubit parity checks and measurement-based, heralded, Bell-state preparation. Our work lays the foundation for hybrid processor–clock devices with neutral atoms and more generally points to a future of practical applications for quantum processors linked with quantum sensors.

DOI: 10.1038/s41586-024-08005-8

Source: https://www.nature.com/articles/s41586-024-08005-8