University of Rochester researchers are using superconductor-metal interfaces to model and learn the quantum physics of a black hole. They show that the metal-superconductor interface can be thought of as an event horizon and Andreev reflection from the interface is analogous to the Hawking radiation in black holes, giving a unitary description of black hole dynamics. Quantum information transfer can be described with Andreev reflection and a final state projection model similar to Horowitz-Maldacena, and Hayden and Preskill’s description of a black hole final state, where the black hole is described as an information mirror. The analogy between Crossed Andreev Reflections and Einstein-Rosen bridges is also discussed. Given these established connections, they conjecture that the final quantum state of a black hole is the Bardeen-Cooper-Schrieffer ground state wavefunction.
Above – Hawking radiation from a black hole in the Horowitz-Maldacena model for black hole evaporation: Virtual particle-antiparticle pairs exist at the event horizon of a black hole. An incoming particle pairs with one of the virtual particles, and enters the black hole interior. This process results in the ejection of a quasiparticle which can escape to infinity.
(a) Information dynamics in Horowitz-Maldacena model shown in the Penrose diagram  of a black hole: The infalling matter takes one Hawking quantum from an entangled particle-antiparticle singlet available at the event horizon. The remaining Hawking quantum escapes to infinity carrying the information. The final state projection onto a singlet inside the horizon ensures that the quantum information has been transferred to the Hawking radiation like quantum teleportation. The arrows indicate that the electron-positron pair at the event horizon teleports the quantum information encoded in the infalling matter to the exterior of the black hole. (b) Information dynamics in Andreev reflection: An electron incident on the metal-superconductor interface from the metal with an energy the superconducting energy gap, can be Andreev reflected as a hole in the metal. A Cooper pair singlet is formed in the superconductor. The quantum information encoded in the incident electron is dynamically transferred to the Andreev reflected hole in analogy with the Horowitz-Maldacena final state projection model.
They establish an analogy between superconductor-metal interfaces and the quantum physics of a black hole, using the proximity effect. They show that the metal-superconductor interface can be thought of as an event horizon and Andreev reflection from the interface is analogous to the Hawking radiation in black holes. They describe quantum information transfer in Andreev reflection with a final state projection model similar to the Horowitz-Maldacena model for black hole evaporation. They also propose the Andreev reflection analog of Hayden and Preskill’s description of a black hole final state, where the black hole is described as an information mirror. The analogy between crossed Andreev reflections and Einstein-Rosen bridges is discussed: our proposal gives a precise mechanism for the apparent loss of quantum information in a black hole by the process of nonlocal Andreev reflection, transferring the quantum information through a wormhole and into another universe. Given these established connections, we conjecture that the final quantum state of a black hole is exactly the same as the ground state wave function of the superconductor/superfluid in the Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity; in particular, the infalling matter and the infalling Hawking quanta, described in the Horowitz-Maldacena model, forms a Cooper pairlike singlet state inside the black hole. A black hole evaporating and shrinking in size can be thought of as the analogue of Andreev reflection by a hole where the superconductor loses a Cooper pair. Their model does not suffer from the black hole information problem since Andreev reflection is unitary. They also relate the thermodynamic properties of a black hole to that of a superconductor, and propose an experiment which can demonstrate the negative specific heat feature of black holes in a growing/evaporating condensate.