Levitated Quantum Diamonds

悬浮量子钻石

• 批准号: ST/W006227/1
• 负责人: Sougato Bose
• 金额: $ 15.48万
• 依托单位: University College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FW006227%2F1
• 关键词: Levitated; Quantum; Diamonds

Atoms and molecules are very well described by quantum mechanics, but what about much larger things? Erwin Schrödinger pointed out that cats have never been shown to exist in a quantum superposition, but recent experiments are pushing back the boundaries of which objects have been shown to do this. The strongest tests require a large mass in a superposition for a long time with a large superposition distance. The superposition distance is the distance between the two components of the superposition. Pioneering experiments have been done with superconductors, superfluids and vibrating cantilevers but the most macroscopic superposition state created so far is a variant of the famous two-slit experiment for molecules made of 2000 atoms. Our project has the ambitious goal of testing whether levitated nanodiamonds made up of more than a million times more atoms can display this quantum behaviour. The most exciting thing about this experimental frontier is that it could, in 10-15 years, lead to a test of quantum gravity. Einstein's general relativity explains gravity and is needed to make GPS work, but we don't know how to combine it with quantum mechanics to explain the gravitational effects produced by a quantum object. Successfully combining these two most fundamental theories of physics would produce a theory of quantum gravity, which has been sought for 100 years. Theories of quantum gravity such as string theory and loop quantum gravity have been proposed, but suffer from a lack of empirical evidence. Physicists such as Stephen Hawking and Roger Penrose worked on black holes and showed they are fertile playgrounds to constrain theories of quantum gravity, but black holes are not practical to experiment on. A new proposal from us and others shows a way to test one key aspect of quantum gravity with a lab experiment on a table-top. The idea is to create two of the nanodiamond Schrödinger cats and see how they interact gravitationally. This project is only possible thanks to the advances already demonstrated by the quantum technology community, and indeed this research will, in time, lead to a new class of more sensitive sensors that would be used to detect acceleration, rotation, tilt, gravity and magnetic fields.Having already published our descriptions for how to test macroscopic quantum mechanics and quantum gravity, we will now transform our preliminary experiments to begin the delivery of these proposals. To reach large superposition distances and long durations we will use diamond nanoparticles (around 800 nm across) containing a single nitrogen vacancy centre (NVC). This follows our proposals which provide a clear route to achieve a superposition distance of over 1000 nm, although our initial experiments will only reach 0.1 pm. Nanodiamonds have been levitated in vacuum using optical traps by us and others, as well as in Paul traps and magnetic traps. We showed that the heating of the diamond by the trapping beam in an optical trap in vacuum is a serious obstacle. To get around this we developed (with collaborator Oliver Williams) large quantities of high-purity nanodiamonds, and have now switched to using a magnetic trap as this further minimises the heating of the levitated diamond. A magnetic trap also provides the inhomogeneous magnetic field which is required to couple the spin to the motion. The core idea is to put the NVC electron spin into a spin superposition because the inhomogeneous magnetic field then provides a superposition of forces on the diamond leading to a spatial superposition. To evidence this, we will then flip the spin to recombine the superposition components for matter-wave interferometry and repeat the interferometry as a function of experimental tilt with respect to gravity to search for interference fringes.

量子力学可以很好地描述原子和分子，但更大的东西呢？薛定谔指出，猫从来没有被证明存在于量子叠加态中，但最近的实验正在推动哪些物体被证明存在这种情况。最强的测试需要一个大的质量在一个叠加很长一段时间与一个大的叠加距离。叠加距离是叠加的两个分量之间的距离。人们已经用超导体、超流体和振动杠杆进行了开创性的实验，但迄今为止创造出的最宏观的叠加态是著名的由2000个原子组成的分子双缝实验的变体。我们的项目有一个雄心勃勃的目标，即测试由超过一百万倍的原子组成的悬浮纳米金刚石是否可以显示这种量子行为。这个实验前沿最令人兴奋的事情是，它可能在10-15年内导致量子引力的测试。爱因斯坦的广义相对论解释了引力，也是使GPS工作所需要的，但我们不知道如何将它与量子力学联合收割机结合起来，解释量子物体产生的引力效应。成功地结合这两个最基本的物理学理论将产生一个量子引力理论，这是100年来一直在寻找的。量子引力的理论，如弦理论和圈量子引力已经被提出，但缺乏经验证据。斯蒂芬·霍金（Stephen Hawking）和罗杰·彭罗斯（Roger Penrose）等物理学家研究了黑洞，并证明它们是限制量子引力理论的肥沃操场，但黑洞并不适合进行实验。我们和其他人提出的一项新提议显示了一种方法，可以通过在桌面上进行实验室实验来测试量子引力的一个关键方面。这个想法是创造两个纳米钻石薛定谔猫，看看它们如何相互作用的引力。这个项目是唯一可能的感谢已经证明了量子技术社区的进步，事实上，这项研究将，在时间，导致一个新的一类更敏感的传感器，将用于检测加速度，旋转，倾斜，重力和磁场.已经发表了我们的描述如何测试宏观量子力学和量子引力，我们现在将改变我们的初步实验，开始交付这些建议。为了达到大的叠加距离和长的持续时间，我们将使用含有单个氮空位中心（NVC）的金刚石纳米颗粒（直径约800 nm）。这遵循了我们的建议，提供了一个清晰的路线，以实现超过1000 nm的叠加距离，尽管我们最初的实验将只达到0.1 pm。我们和其他人已经使用光学陷阱以及Paul陷阱和磁陷阱将纳米金刚石悬浮在真空中。我们表明，真空光学陷阱中的捕获光束对钻石的加热是一个严重的障碍。为了解决这个问题，我们（与合作者奥利弗威廉姆斯）开发了大量的高纯度纳米金刚石，现在已经改用磁阱，因为这进一步减少了悬浮金刚石的加热。磁阱还提供了将自旋耦合到运动所需的非均匀磁场。其核心思想是将NVC电子自旋置于自旋叠加中，因为不均匀的磁场随后在金刚石上提供了导致空间叠加的力的叠加。为了证明这一点，我们将翻转自旋，重新组合物质波干涉测量的叠加分量，并重复干涉测量作为相对于重力的实验倾斜的函数，以寻找干涉条纹。

项目成果

Relaxation of experimental parameters in a quantum-gravity-induced entanglement of masses protocol using electromagnetic screening

使用电磁屏​​蔽在量子引力引起的质量纠缠协议中放宽实验参数

• DOI: 10.1103/physrevresearch.5.043170
• 发表时间: 2023
• 期刊: Physical Review Research
• 影响因子: 4.2
• 作者: Schut M