Interplay of Gravity and Quantum Mechanical Superpositions

物理学中两个最基本且得到充分验证的理论是描述引力的广义相对论和描述我们已知的其他三种基本力的量子力学。一个关于引力的一致的量子力学理论仍然让我们困惑。一段时间以来，量子力学和引力的统一一直是人们热切期望的前景。随着量子场论实现了量子力学和狭义相对论的统一，广义相对论在某种程度上也不可避免地具有量子性质。为了确定情况是否如此，已经提出了许多测试，但没有找到明确的答案。考虑到这一点，该项目将寻求，除其他事项外，帮助回答重力是否，至少在其低能量极限下，本质上是量子的。一些人开始质疑引力是否从根本上是一个量子实体，这就提出了它是否可能是一个经典的场/背景与量子力学愉快共存的可能性。如果万有引力确实是经典的，那么最引人注目的领域可能是，当物质处于特殊量子态时，比如处于高度离域叠加态时，作为万有引力的来源，我们将遭受预测引力场的痛苦。为此，这个项目的主要目标是设计一些实验，将介社会物体的量子叠加态与引力结合起来，或者将它们作为引力的来源，并以此推断引力的量子本质。我们还将研究这些实验的潜力，以实现精确的加速度测量和重力测量，并使引力定律和牛顿常数在短距离内的确定成为可能。目前的项目将寻求(i)扩展上述重力加速度测量的建议，用于压缩态和其他工程非经典量子态的叠加，以便在给定的能量投资下优化测量的精度。（ii）将上述建议延伸至介观体系的宏观边界，探索量子体系与引力之间的边界。特别是，从纳米半径珠到微米半径珠的外推，可以作为可测量引力场的起源，将被检查。为此，将采用一种新的方法，通过非均匀电场通过晶体各向异性耦合到自旋状态来分裂空间位置。（三）将对一个空间区域内系统的不同能量-动量态叠加的退相干性进行理论计算，这种叠加是由于周围其他系统的存在和波动而产生的，这些系统在引力作用下与之耦合。（iv）通过使一个探测质量接近另一个处于高度非经典状态的质量，我们将研究牛顿常数的精度，以及牛顿定律在短距离上的潜在修正，例如来自额外维度，可以确定。(v)将这些研究扩展到两个干涉仪系统，以便包括双部纠缠，以进一步探索重力如何处理高量子，大质量系统。我们将考虑两个质量在高度非高斯状态下的相互作用（由项目早期建立的方法准备），以生成某种形式的“无漏洞”引力量子特性测试。

The two most fundamental and well-verified theories of physics are General Relativity,which describes gravity, and Quantum Mechanics, which describes the other threefundamental forces known to us. A consistent quantum mechanical theory of gravity stilleludes us. The unification of quantum mechanics and gravity has been a greatly desiredprospect for some time. With the unification of quantum mechanics and special relativitybeing achieved with Quantum Field Theory, it has been seen as inevitable for GeneralRelativity to also be, at some level, quantum in nature. To determine if this is the casenumerous tests have been proposed -- however no definitive answers have beenfound. With this in mind this project will seek, among other things, to help answer whethergravity, at least in its low energy limit, is fundamentally quantum in nature.Some have started to question whether gravity is fundamentally a quantum entity, raisingthe possibility of whether it could be a classical field/background happily co-existing withquantum mechanics. Perhaps the most striking arena where we will suffer if gravity isindeed classical is to predict the gravitational field when matter in peculiarly quantumstates, say in highly delocalized superpositions, acts as the source of gravity. To this end,the broad aim of this project will be to design experiments which couple quantumsuperpositions of states of mesosocpic objects to gravity, or use them as sources of gravityand through that infer about the quantum nature of gravity. We will also investigate thepotential of these experiments to enable both precision accelerometry and gravimetry andto enable the determination of gravitational force law and Newton's constant over shortdistances.The current project will seek to(i) Extend the above gravitational accelerometry proposals for superpositions ofsqueezed states and other engineered non-classical quantum states so as tooptimize the precision of measurements for a given investment of energy. (ii) Extend the above proposals up to the macroscopic boundary of the mesoscopicregime to explore the boundary between the quantum regime and gravity. Inparticular, the extrapolation from nano-meter radii beads to micro-meter radiibeads, which can serve as the origin of measurable gravitational fields, will beexamined. For this purpose, a new way to split the spatial position throughinhomogeneous electric fields coupling to spin states through crystalanisotropies, will be used. (iii) A theoretical calculation of the decoherence of a superposition of distinctenergy-momentum states of a system in one region of space due to the presenceand fluctuations of other surrounding systems that couple gravitationally to itwill be made. (iv) By bringing a probe mass in proximity to another mass in a highly non-classicalstate, we are going to investigate the precisions to which the Newton's ConstantG, and potential corrections to Newton's law for short distances, stemming, forexample from extra dimensions, could be determined. (v) Expand these investigations to two interferometer systems in order to includebipartite entanglement to further explore how gravity addresses a highlyquantum, massive system. We will consider the interactions of two masses inhighly non-Gaussian states (prepared by methodologies founded earlier in theproject) to generate some form of 'loophole free' tests for the quantum natureof gravity.