No experiment to date has provided evidence for quantum features of the gravitational interaction. Recently proposed tests suggest looking for the generation of quantum entanglement between massive objects as a possible route towards the observation of such features. Motivated by advances in optical cooling of mirrors, here we provide a systematic study of entanglement between two masses that are coupled gravitationally. We first consider the masses trapped at all times in harmonic potentials (optomechanics) and then the masses released from the traps. This leads to the estimate of the experimental parameters required for the observation of gravitationally induced entanglement. The optomechanical setup demands LIGO-like mirrors and squeezing or long coherence times, but the released masses can be light and accumulate detectable entanglement in a timescale shorter than their coherence times. No macroscopic quantum superposition develops during the evolution. We discuss the implications from such thought experiments regarding the nature of the gravitational coupling.

迄今为止，还没有实验提供引力相互作用的量子特征的证据。最近提出的测试建议寻找在大型物体之间产生量子纠缠的可能性，以此作为观察此类特征的可能途径。受反射镜光学冷却技术进步的推动，在这里，我们对重力耦合的两个质量之间的纠缠进行了系统的研究。我们首先考虑始终被谐波电位（光力学）捕获的质量，然后考虑从陷阱释放的质量。这导致对观察引力纠缠所需的实验参数的估计。光机械设置需要像LIGO一样的镜面，并且需要挤压或较长的相干时间，但是释放的质量可能很轻，并且在比其相干时间短的时间范围内积累可检测的纠缠。在进化过程中没有宏观的量子叠加。我们讨论了这种思想实验对引力耦合性质的影响。