论文标题
Loschmidt Echo的变分量子计量学
Variational Quantum Metrology with Loschmidt Echo
论文作者
论文摘要
通过利用量子机械效应，例如叠加和纠缠，量子计量学有望比经典策略更高的精度。但是，实现量子优势实际上具有挑战性。这主要是由于工程非经典探针状态的困难以及在实践中进行非平凡的测量，尤其是在大量颗粒中。在这里，我们提出了一个具有对称变分量子电路的可扩展方案，该方案与Loschmidt Echo相同，由正向和向后演化组成。我们表明，在这种方案中，可以从洛斯米德回声的测量信号有效地获得量化精度极限的量子渔民信息。我们通过实验性地在10旋量子处理器的集合上实现了该方案，并成功地达到了理论极限附近的精度，该限制的表现优于12.4 dB的标准量子极限。该方案可以在各种嘈杂的中间尺度量子设备上有效实施，该设备提供了有希望的例程来证明量子优势。
By utilizing quantum mechanical effects, such as superposition and entanglement, quantum metrology promises higher precision than the classical strategies. It is, however, practically challenging to realize the quantum advantages. This is mainly due to the difficulties in engineering non-classical probe state and performing nontrivial measurement in practise, particularly with a large number of particles. Here we propose a scalable scheme with a symmetrical variational quantum circuit which, same as the Loschmidt echo, consists of a forward and a backward evolution. We show that in this scheme the quantum Fisher information, which quantifies the precision limit, can be efficiently obtained from a measurement signal of the Loschmidt echo. We experimentally implement the scheme on an ensemble of 10-spin quantum processor and successfully achieves a precision near the theoretical limit which outperforms the standard quantum limit with 12.4 dB. The scheme can be efficiently implemented on various noisy intermediate-scale quantum devices which provides a promising routine to demonstrate quantum advantages.
