LEvitated MAgnets for QUantum Metrology

理论上，悬浮微磁体已经被提出作为许多混合量子系统的组成部分，以及作为扭矩、力或磁场的超低噪声传感器，能够在能量分辨率方面大大优于传统的量子限制设备。最近的开创性实验支持了这种突出的潜力，但它远未得到充分证明。在这个项目中，我们旨在系统地研究基于悬浮微磁体的传感器。我们将探索各种悬浮平台，如基于迈斯纳效应的超导陷阱，用于磁捕获的片上电路，自由落体和带电微磁体的保罗陷阱，并利用不同量子系统或器件的耦合，如金刚石氮空位中心和squid。我们将主要研究悬浮磁体的振动和旋转运动，并将重点放在超低扭矩和磁场的检测上，目的是展示前所未有的能量分辨率。特别是，我们的目标是证明与介观磁体的类原子拉莫尔进动相对应的最敏感的状态，这是一种由本征自旋的量子性质引起的特殊效应。从理论上讲，我们期望在能量分辨率方面取得比目前技术水平更大的进步。例如，我们期望在数量级上克服能量分辨率极限，这是一个半经验的界限，似乎所有现有的量子磁力计都能满足。然后，我们将在基础物理学中非常感兴趣的特定科学案例中利用开发的传感器的潜力，例如探测超越标准模型的新物理产生的奇异相互作用。作为一个长期的愿景，我们将研究未来在太空中使用量子自旋系统（特别是悬浮磁铁）测试广义相对论的可能性。我们的目标是在爱因斯坦电梯中进行初步的原理证明演示，在那里可以以最干净的方式观察自由落体磁铁的拉莫尔进动。该项目将受益于该联盟的高度横向和跨学科性质，该联盟聚集了来自钻石NV中心、离子阱、冷原子、混合量子系统、squid、光力学和光磁计等不同领域的悬浮量子磁力学科学家。

Levitated micromagnets have been theoretically proposed as building blocks of a number of hybrid quantum systems and as ultralow-noise sensors of torque, force or magnetic field, capable of largely outperforming conventional quantum-limited devices in terms of energy resolution. This outstanding potential is supported by recent pioneering experiments, yet it is far from being fully demonstrated. In this project we aim at a systematic investigation of sensors based on levitated micromagnets. We will explore various levitation platforms, such as superconducting traps based on the Meissner effect, on-chip circuits for magnetic trapping, free-fall, and Paul traps for charged micromagnets, and exploit coupling to different quantum systems or devices, such as diamond Nitrogen-Vacancy (NV) centers and SQUIDs. We will primarily investigate the librational and rotational motion of the levitated magnets and focus on the detection of ultralow torque and magnetic fields, with the goal of demonstrating unprecedented energy resolution. In particular, we aim at demonstrating the most sensitive regime corresponding to atom-like Larmor precession of a mesoscopic magnet, a peculiar effect arising from the quantum nature of intrinsic spin. Theoretically we expect to achieve outstanding improvement over the state of the art in terms of energy resolution. For instance, we expect to overcome by orders of magnitude the Energy Resolution Limit, a semiempirical bound which appears to be satisfied by all existing quantum magnetometers. We will then exploit the potential of the developed sensors in specific science cases of great interest in fundamental physics, such as probing exotic interactions arising from new physics beyond the standard model. As a long-term vision, we will investigate the potential for future tests of General Relativity with quantum spin systems (specifically, levitated magnets) in space. We aim at an initial proof-of-principle demonstration in the Einstein-Elevator, where the Larmor precession of a free-falling magnet can be observed in the cleanest conceivable way. The project will benefit from the highly transversal and interdisciplinary nature of the consortium, which gathers scientists converging to levitated quantum magnetomechanics from the diverse fields of diamond NV centers, ion traps, cold atoms, hybrid quantum systems, SQUIDs, optomechanics and optical magnetometry.