On-demand analog space-time in superconducting networks: grey holes, dynamical instability and exceptional points

TL;DR

This paper demonstrates how superconducting circuits can simulate on-demand spacetime geometries, revealing phenomena like grey holes, dynamical instabilities, and exceptional points that challenge traditional black hole analogs.

Contribution

It introduces a method to implement tunable spacetime geometries in superconducting lattices, enabling the study of horizon dynamics and exceptional points in quantum simulations.

Findings

Sharp metric changes induce trans-Planckian regimes and unstable quantum fluctuations.

Exceptional points enable creation of pure black or white hole horizons.

Instabilities manifest as exponential bursts of charge and phase fluctuations.

Abstract

There has been considerable effort to mimic analog black holes and wormholes in solid state systems. Lattice realizations in particular present specific challenges. One of those is that event horizons in general have both white and black hole (grey hole) character, a feature guaranteed by the Nielsen-Ninomiya theorem. We here explore and extend the capability of superconducting circuit hardware to implement on-demand spacetime geometries on lattices, combining nonreciprocity of gyrators with the nonlinearity of Josephson junctions. We demonstrate the possibility of the metric sharply changing within a single lattice point, thus entering a regime where the modulation of system parameters is "trans-Planckian", and the Hawking temperature ill-defined. Instead of regular Hawking radiation, we find an instability in the form of an exponential burst of charge and phase quantum fluctuations over short time scales - a robust signature even in the presence of an environment. Moreover, we present a loop-hole for the typical black/white hole ambiguity in lattice simulations: exceptional points in the dispersion relation allow for the creation of pure black (or white) hole horizons, at the expense of a radical change in the dynamics of the wormhole interior.