Triggiani Danilo, Tamma Vincenzo
School of Mathematics and Physics, University of Portsmouth, Portsmouth PO1 3QL, UK.
Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 3FX, UK.
Sensors (Basel). 2022 Mar 30;22(7):2657. doi: 10.3390/s22072657.
Quantum sensing and quantum metrology propose schemes for the estimation of physical properties, such as lengths, time intervals, and temperatures, achieving enhanced levels of precision beyond the possibilities of classical strategies. However, such an enhanced sensitivity usually comes at a price: the use of probes in highly fragile states, the need to adaptively optimise the estimation schemes to the value of the unknown property we want to estimate, and the limited working range, are some examples of challenges which prevent quantum sensing protocols to be practical for applications. This work reviews two feasible estimation schemes which address these challenges, employing easily realisable resources, i.e., squeezed light, and achieve the desired quantum enhancement of the precision, namely the Heisenberg-scaling sensitivity. In more detail, it is here shown how to overcome, in the estimation of any parameter affecting in a distributed manner multiple components of an arbitrary -channel linear optical network, the need to iteratively optimise the network. In particular, we show that this is possible with a single-step adaptation of the network based only on a prior knowledge of the parameter achievable through a "classical" shot-noise limited estimation strategy. Furthermore, homodyne measurements with only one detector allow us to achieve Heisenberg-limited estimation of the parameter. We further demonstrate that one can avoid the use of any auxiliary network at the price of simultaneously employing multiple detectors.
量子传感和量子计量学提出了用于估计物理性质（如长度、时间间隔和温度）的方案，实现了超越经典策略可能性的更高精度水平。然而，这种增强的灵敏度通常是有代价的：使用处于高度脆弱状态的探测器、需要根据我们想要估计的未知性质的值自适应地优化估计方案，以及有限的工作范围，这些都是阻碍量子传感协议在实际应用中使用的挑战示例。这项工作回顾了两种可行的估计方案，它们利用易于实现的资源（即压缩光）来应对这些挑战，并实现所需的量子精度增强，即海森堡标度灵敏度。更详细地说，本文展示了在估计以分布式方式影响任意信道线性光学网络多个组件的任何参数时，如何克服对网络进行迭代优化的需求。特别是，我们表明仅基于通过“经典”散粒噪声受限估计策略可实现的参数先验知识对网络进行单步自适应就可以做到这一点。此外，仅使用一个探测器的零差测量使我们能够实现对参数的海森堡极限估计。我们进一步证明，以同时使用多个探测器为代价，可以避免使用任何辅助网络。
