EAGER: Generating Motional Quantum States of an Optically Trapped Diamond Nanocrystal Containing Nitrogen Vacancy Centers

日常生活中物体的运动似乎遵循简单的规律（牛顿定律）。例如，冰球在冰上滑行时，除非有外力作用，否则它会保持匀速直线运动。在牛顿定律中，你总是可以测量冰球运动的一切，比如它的位置和速度，而不影响冰球的运动。似乎任何物体都是如此，无论是像地球这样大的物体，还是像原子这样小的物体。然而，这不是自然的运作方式；非常小的物体，如原子或电子，似乎遵循一套不同的规则，称为量子力学。量子力学预言奇怪的事情会发生，例如，一个原子可以同时在两个地方，直到它的位置被实际测量。尽管这些规则很奇怪，但它们使电脑和手机中的电子设备正常工作，所以我们知道它们是准确的。为什么冰球没有这种奇怪的量子行为？与其他物体的相互作用往往会掩盖量子力学对比原子大得多的物体的影响。这个项目支持的研究小组将把一个微小的钻石晶体悬浮在一个几乎没有空气的房间里，以尽量减少它与其他物体的相互作用，并扩大量子力学适用的尺寸限制。这些实验的结果将提高我们对量子力学的理解，量子力学是我们几乎所有现代技术的基础。这个程序最终寻求在一个机械系统中产生“猫态”，在这个系统中，一个物体处于两个不同位置的量子叠加态。自80年前著名的薛定谔思想实验以来，这一挑战一直困扰着物理学家。该项目支持的研究人员将证明，含有氮空位（NV）缺陷中心的捕获金刚石纳米晶体是创建这种运动量子态的近乎理想的平台。特别是，他们将努力展示该系统的四个关键功能。首先，金刚石纳米晶体必须以超高质量因子(Q)被困在真空中。其次，必须有可能操纵和读出NV中心的自旋状态。第三，NV中心自旋态必须与机械运动态耦合。最后，机械运动必须冷却到接近基态，以初始化系统到一个已知的配置。实验首先将金刚石纳米晶体装入陷阱中。接下来，用光学方法读取捕获的纳米金刚石中NV中心的自旋态，并用微波驱动器对其进行操纵。最后，机械运动通过外加磁场梯度耦合到NV中心自旋。机械运动的超高Q值和NV中心的量子控制相结合，使得含有NV的被困纳米钻石成为产生运动量子态的独特系统。该系统的发展对于探索量子力学的基本极限和新的运动量子态的性质具有重要的价值。

The motions of objects in everyday life appear to follow simple rules (Newton's laws). For example, a hockey puck gliding across ice tends to keep moving in a straight line at constant speed unless a force acts on it. It is implicit in Newton's laws that you can always measure everything about the puck's motion, such as its position and its speed, without affecting the motion. It seems that the same should be true of any object, whether it is huge like the planet earth or tiny like an atom. However, this is not how nature works; very small objects, such as an atom or an electron, seem to obey a different set of rules, called quantum mechanics. Quantum mechanics predicts that strange things can happen, for example, an atom can have properties of being in two places at the same time, until its position is actually measured. As strange as those rules are, they make the electronics in computers and cell phones work, so we know they are accurate. Why don't hockey pucks have this strange quantum behavior? Interaction with other objects tends to hide the effects of quantum mechanics for objects much larger than atoms. The research team supported by this project will levitate a tiny diamond crystal in a chamber with almost no air remaining to minimize its interaction with other objects and stretch the size limits over which quantum mechanics does apply. The results of these experiments will improve our understanding of quantum mechanics, which is the foundation on which almost all our modern technology is based. This program ultimately seeks to produce "cat states" in a mechanical system, where an object is in a quantum superposition of two different positions. This is a challenge which has puzzled physicists since the famous thought experiments of Schrodinger, 80 years ago. Researchers supported by this program will demonstrate that a trapped diamond nanocrystal containing nitrogen-vacancy (NV) defect centers is a nearly ideal platform for creating such motional quantum states. In particular, they will work towards demonstrating four critical capabilities of this system. First, the diamond nanocrystal must be trapped in vacuum with an ultra-high quality factor (Q). Second, it must be possible to manipulate and read out the spin state of the NV centers. Third, the NV center spin states must couple to the state of the mechanical motion. Last, the mechanical motion must be cooled to near the ground state to initialize the system to a known configuration. The experiments begin by loading a diamond nanocrystal into the trap. Next, the spin state of NV centers in the trapped nanodiamond will be read optically and manipulated with a microwave drive. Finally, the mechanical motion is coupled to the NV center spins through externally-imposed magnetic field gradients. The combination of the ultra high Q of the mechanical motion and quantum control of the NV centers makes trapped, NV-containing nanodiamonds a unique system for generating motional quantum states. The development of this system could be of great value in exploring the fundamental limits of quantum mechanics and the properties of novel motional quantum states.