论文标题
具有XX+YY耦合和Z读数系统的改进的量子层析成像
Improved Quantum State Tomography for the Systems with XX+YY Couplings and Z Readouts
论文作者
论文摘要
量子设备通过状态层析成像表征在验证量子硬件和处理量子信息方面起着重要作用，但它需要测量的指数数量。对于具有XX+YY型耦合和Z读数的系统，例如超导量子计算（SQC）系统，使用单Qubit读取操作的传统量子状态层析成像（QST）至少需要$ 3^n $测量设置，以重建$ n $ qubit State。在这项工作中，我提出了改进的QST，通过添加2 Quibit Evolutions作为读取操作，并使用整数编程优化获得了最佳的层析成像方案。我分别将新方案应用于SQC系统，其近距离，二维和全面连接量。它表明，与传统QST相比，该方法可以将测量数量减少60％以上。此外，通过数值模拟进行了与实验可行性和鲁棒性的传统方案的比较。已经发现，新计划具有良好的可实施性，并且比传统方案可以实现可比甚至更好的准确性。可以预期，来自相关领域的实验人员可以直接利用现成的结果来重建研究中涉及的量子状态。
Quantum device characterization via state tomography plays an important role in both validating quantum hardware and processing quantum information, but it needs the exponential number of the measurements. For the systems with XX+YY-type couplings and Z readouts, such as superconducting quantum computing (SQC) systems, traditional quantum state tomography (QST) using single-qubit readout operations at least requires $3^n$ measurement settings in reconstructing an $n$-qubit state. In this work, I proposed an improved QST by adding 2-qubit evolutions as the readout operations and obtained an optimal tomographic scheme using the integer programming optimization. I respectively apply the new scheme on SQC systems with the Nearest-Neighbor, 2-Dimensional, and All-to-All connectivities on qubits. It shows that this method can reduce the number of measurements by over 60% compared with the traditional QST. Besides, comparison with the traditional scheme in the experimental feasibility and robustness against errors were made by numerical simulation. It is found that, the new scheme has good implementability and it can achieve comparable or even better accuracy than the traditional scheme. It is expected that the experimentalist from the related fields can directly utilize the ready-made results for reconstructing quantum states involved in their research.
