For example, long-wavelength gravitational waves propagating on otherwise flat (uncurved) space can be described as excitations of specific quantum states described by the loop quantum gravity theory.

• 比如说，波长较长的重力波，在平坦（没被弯曲）的时空中传播，便可以描述为环圈量子重力理论中特定量子态的激发状态。