CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China.
CAS Center For Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China.
Phys Rev Lett. 2019 Jul 26;123(4):040501. doi: 10.1103/PhysRevLett.123.040501.
The advantage of quantum metrology has been experimentally demonstrated for phase estimations where the dynamics are commuting. General noncommuting dynamics, however, can have distinct features. For example, the direct sequential scheme, which can achieve the Heisenberg scaling for the phase estimation under commuting dynamics, can have even worse performances than the classical scheme when the dynamics are noncommuting. Here we realize a scalable optimally controlled sequential scheme, which can achieve the Heisenberg precision under general noncommuting dynamics. We also present an intuitive geometrical framework for the controlled scheme and identify sweet spots in time at which the optimal controls used in the scheme can be prefixed without adaptation, which simplifies the experimental protocols significantly. We successfully implement the scheme up to eight controls in an optical platform and demonstrate a precision near the Heisenberg limit. Our work opens the avenue for harvesting the power of quantum control in quantum metrology, and provides a control-enhanced recipe to achieve the Heisenberg precision under general noncommuting dynamics.
量子计量学的优势在相位估计方面得到了实验验证，其中动力学是可交换的。然而，一般的非交换动力学可能具有不同的特征。例如，在可交换动力学下，直接顺序方案可以实现相位估计的海森堡标度，但在非交换动力学下，其性能甚至比经典方案更差。在这里，我们实现了一种可扩展的最优控制顺序方案，可以在一般非交换动力学下实现海森堡精度。我们还为控制方案提出了一个直观的几何框架，并确定了时间上的最佳点，在这些点上，无需自适应即可预先设置方案中使用的最优控制，这大大简化了实验方案。我们成功地在光学平台上实现了多达 8 个控制，并演示了接近海森堡极限的精度。我们的工作为在量子计量学中利用量子控制的优势开辟了道路，并提供了一种控制增强的方案，以在一般非交换动力学下实现海森堡精度。
