Cracking the invisible cloak by using the temporal steering inequality

Invisible cloaks provide a way to hide an object under the detection of waves. A perfect cloak guides the incident waves through the cloaking shell without any distortion. In most cases, some important quantum degrees of freedom, e.g. electron spin or photon polarization, are not taken into account when designing a cloak. Here, we propose to use the temporal steering inequality of these degrees of freedom to detect the existence of an invisible cloak.