Black holes and quantum coherence

Robert M. Wald

We attempt to gain some insight into the issue of whether pure states evolve to density matrices in the black hole evaporation process by examining the mode functions of the particles entering the black hole which are correlated with the particles which escape to infinity. We show that these particles enter the black hole singularity at relatively early times. This tends to support the view that pure states evolve to density matrices, i.e., that in this process quantum coherence is lost.

John P. Preskill

Richard Howl, Ali Akil, Hlér Kristjánsson +2 more

The interplay between black holes and quantum information has revealed deep connections between gravity and quantum mechanics. For example, the classical spacetime geometry of a black hole has been shown to degrade quantum entanglement shared by nearby observers, one of whom is in free fall. Here, we examine how this picture changes when the black hole’s mass degrees of freedom are allowed to exist in a coherent quantum superposition, corresponding to a superposition of distinct spacetime geometries. We show that such quantum coherence can mitigate the loss of entanglement between nearby observers, thereby enhancing the performance of quantum communication protocols operating in the vicinity of the black hole. When treated classically, black holes degrade the quantum entanglement shared between nearby observers. The authors find that placing the black hole’s mass - and hence its spacetime - in a quantum superposition can act as a resource to counter this degradation.

ubir Sachde, Guoliang Xu, C. Broholm +6 more

Akio Hosoya

Richard Howl, Ali Akil, Hlér Kristjánsson +2 more

The interplay between black holes and quantum information has revealed deep connections between gravity and quantum mechanics. For example, the classical spacetime geometry of a black hole has been shown to degrade quantum entanglement shared by nearby observers, one of whom is in free fall. Here we examine how this picture changes when the black hole's mass degrees of freedom are allowed to exist in a coherent quantum superposition, corresponding to a superposition of distinct spacetime geometries. We show that such quantum coherence can mitigate the loss of entanglement between nearby observers, thereby enhancing the performance of quantum communication protocols operating in the vicinity of the black hole.