Quantum thermometry at ultracold temperatures (Ref: 4342-6)

量子测温是一个快速发展的领域，旨在建立精确的温度限制时，量子效应是重要的。低温下的强耗散相互作用可以在温度探针和被测样品之间产生量子关联。为了精确地描述探针的状态，人们可以求助于开放量子系统理论。探针的热灵敏度可以用量子估计理论工具箱来量化。这为研究测温实验提供了一个强有力的理论框架。鉴于超冷测量的严格限制，理解这些界限的起源并利用这种理解来优化当前的实验是至关重要的。量子测温技术是实现这一目标的理想工具。这个理论项目的核心目标是发展新的理论，将有助于将量子测温技术融入当前的低温实验。为此，我们将把开放量子系统理论中强大的微观模型与贝叶斯估计方法相结合。我们将使用这个新的框架来设计实验测温技术的升级，并提高其精度和时间效率。为了做到这一点，我们将重新制定最近开发的贝叶斯方法，用于在失衡的情况下。这将有助于在特殊实验兴趣极端温度和有限耦合的情况下对噪声数据进行最佳和独立于平台的处理。因此，这些结果将与基于冷原子的技术的热控制相关，但也与捕获离子、超导量子比特或量子光学力学相关。开放量子系统的理论及其热力学特性将是这个项目的第二个主要参与者。它提供了一个有效的和易于处理的近似动力学的个别量子系统与他们的周围环境。虽然许多努力已经进入研究开放系统的热力学弱热接触与线性浴，非线性和强耗散的制度仍然几乎未被探索。这些可能会揭示丰富的新物理学，并为提高量子热力学设备的能量性能提供大量机会。此外，真实设备的精确建模当然需要超越弱线性耗散。然而，这将需要一整套新的/重新利用的开放系统工具，例如，马尔可夫嵌入方法，整体平衡态的微扰展开，或精确运动方程的截断。

Quantum thermometry is a rapidly growing field aimed at establishing precision limits on thermometry when quantum effects are important. Strong dissipative interactions at low temperatures can create quantum correlations between a temperature probe and the measured sample. In order to accurately describe the state of the probe, one may resort to the theory of open quantum systems. The thermal sensitivity of the probe can be then quantified with the toolbox of quantum estimation theory. This provides a robust theoretical framework to study thermometry experiments. Given the stringent limitations on ultracold measurements, it is essential to understand the origin of these bounds, and harness that understanding to optimise current experiments. Quantum thermometry appears as the ideal vehicle to achieve it.The core objective of this theoretical project is to develop new theory that will help integrate quantum thermometry into current low-temperature experiments. To do so, we will blend the powerful microscopic modelling from the theory of open quantum systems with Bayesian estimation methods. We will use this new framework to devise upgrades to experimental thermometric techniques and to boost their precision and time-efficiency. To do so, we will reformulate recently developed Bayesian methods for use in out-of-equilibrium situations. This will facilitate optimal and platform-independent processing of noisy data in situations of particular experimental interest-extreme temperatures and finite couplings. The outcomes will thus be relevant for thermal control on cold-atom based technologies, but also trapped ions, superconducting qubits, or quantum optomechanics. The theory of open quantum systems and thier thermodynamic characterisation will be the second major player in this projetc. It provides an effective and tractable approximation to the dynamics of individual quantum systems in contact with their surroundings. While much effort has gone into studying the thermodynamics of open systems in weak thermal contact with linear baths, the regimes of non-linear and strong dissipation still remain virtually unexplored. These are likely to unveil rich new physics, as well as offering a plethora of opportunities for boosting the energetic performance of quantum-thermodynamic devices. Besides, accurate modelling of real-life devices certainly requires going beyond weak linear dissipation. However, this will require a whole set of new/repurposed open-system tools based on, e.g., Markovian embedding methods, perturbative expansions of global equilibrium states, or truncation of hierarchies of exact equations of motion.