Decoherence from a superconducting "horizon"

In a recent paper [1], Danielson et al. demonstrated that the mere presence of a black hole causes universal decoherence of quantum superpositions (dubbed the DSW decoherence) within a finite amount of time. This result has profound implications for the interplay of quantum mechanics and gravity. We analyze decoherence in a superconducting analog [2] 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 supercondutor by a normal metal bridge of varying length. At absolute zero, 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. Various metrics for decoherence are considered and the dependence on the distance of the SN interface to the interferometer is analyzed. Our results open a new path to study black hole quantum physics on earth via analog studies.

[1] D. L. Danielson, G. Satishchandran, and R. M. Wald, “Black holes decohere quantum superpositions”, International Journal of Modern Physics D 31, 2241003 (2022).

[2] S. K. Manikandan and A. N. Jordan, “Andreev reflections and the quantum physics of black holes”, Physical Review D 96, 124011 (2017).