Decoherence and the Reemergence of Coherence From a Superconducting "Horizon"

In a recent paper arXiv:2205.06279, Danielson et al. demonstrated that the mere presence of a black hole causes universal decoherence of quantum superpositions (dubbed the DSW decoherence). This result has profound implications for the interplay of quantum mechanics and gravity. We analyze decoherence in a superconducting analogue arXiv:1709.06154 of the event horizon of a black hole, where Andreev reflection plays the role of Hawking radiation. We consider a normal metal interferometer threaded by an Aharonov-Bohm flux, where one of the arms of the interferometer is coupled to a superconductor by a tunnel coupling of varying strength. At absolute zero and for weak coupling, we find that the scattering states of the interferometer are decohered by Andreev reflection, a nontrivial manifestation of the proximity effect analogous to DSW decoherence from the event horizon of a black hole. However, for increasing coupling strength to the superconductor, we find a reemergence of coherence via resonant tunneling through Andreev bound states. This suggests the existence of an analogue gravitational phenomenon wherein transmission mediated by virtual Hawking radiation leads to a reemergence of coherence in an interferometer placed within a few Compton wavelengths of a black hole's event horizon. Our results open a new path to study black hole quantum physics on earth via analogue studies.

Source: arXiv:2603.16765v1 - http://arxiv.org/abs/2603.16765v1 PDF: https://arxiv.org/pdf/2603.16765v1 Original Link: http://arxiv.org/abs/2603.16765v1