Repetitive Readout and Real-Time Control of Nuclear Spin Qubits in 171Yb Atoms
Repetitive Readout and Real-Time Control of Nuclear Spin Qubits in 171Yb Atoms
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DOI：
10.1103/prxquantum.4.030337
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发表时间：
2023-05
期刊：
影响因子：
9.7
通讯作者：
W. Huie;Lintao Li;Neville Chen;Xiye Hu;Zhubing Jia;Won Kyu Calvin Sun;J. Covey
中科院分区：
文献类型：
--
作者：
W. Huie;Lintao Li;Neville Chen;Xiye Hu;Zhubing Jia;Won Kyu Calvin Sun;J. Covey
我们展示了高保真度重复投影测量的核自旋量子比特的中性镱-171（$^{171}$Yb）原子阵列。我们表明，量子比特状态可以以0.995（4）的保真度测量，条件是使其处于与测量结果对应的状态，对于单个镊子的概率为0.993（6），在整个阵列上平均为0.981（4）。这是通过在磁场为B=58$ G的条件下，其中一个核自旋量子位态与光学激发态的近乎完美的循环来实现的，从而在荧光读出期间产生约10 ^5 $的亮/暗对比度。性能进一步提高为$\sim1/B^2$。0.98（1）的状态平均读出存活率受到到暗态的非共振散射的限制，并且可以通过在电路结束时测量原子数或在电路期间通过执行两个量子位状态的测量经由后选择来解决。我们结合联合收割机投影测量与高保真度旋转的核自旋量子比特通过交流磁场探索几个典型的情况下，包括非交换性的测量正交基地，和量子芝诺机制中的测量“冻结“相干演化。最后，我们采用实时前馈重复确定性地准备在$+z$或$-z$方向的量子比特初始化后，在一个正交的基础上，并在$z$-基础上进行投影测量。这些能力构成了迈向具有原子阵列的自适应量子电路的重要一步，例如基于测量的量子计算，快速多体状态准备，全息动力学模拟和量子纠错。
We demonstrate high fidelity repetitive projective measurements of nuclear spin qubits in an array of neutral ytterbium-171 ($^{171}$Yb) atoms. We show that the qubit state can be measured with a fidelity of 0.995(4) under a condition that leaves it in the state corresponding to the measurement outcome with a probability of 0.993(6) for a single tweezer and 0.981(4) averaged over the array. This is accomplished by near-perfect cyclicity of one of the nuclear spin qubit states with an optically excited state under a magnetic field of $B=58$ G, resulting in a bright/dark contrast of $\approx10^5$ during fluorescence readout. The performance improves further as $\sim1/B^2$. The state-averaged readout survival of 0.98(1) is limited by off-resonant scattering to dark states and can be addressed via post-selection by measuring the atom number at the end of the circuit, or during the circuit by performing a measurement of both qubit states. We combine projective measurements with high-fidelity rotations of the nuclear spin qubit via an AC magnetic field to explore several paradigmatic scenarios, including the non-commutivity of measurements in orthogonal bases, and the quantum Zeno mechanism in which measurements"freeze"coherent evolution. Finally, we employ real-time feedforward to repetitively deterministically prepare the qubit in the $+z$ or $-z$ direction after initializing it in an orthogonal basis and performing a projective measurement in the $z$-basis. These capabilities constitute an important step towards adaptive quantum circuits with atom arrays, such as in measurement-based quantum computation, fast many-body state preparation, holographic dynamics simulations, and quantum error correction.