arXiv subjects

Eric J. Sung

Publications and source records attributed to Eric J. Sung.

3 recordsLinked to original sources

arXiv2026

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). 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 temperature 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.

quant-ph↗

arXiv2025

Generalized Boundary Conditions for the qBounce Experiment

Discrepancies between theory and recent qBounce data have prompted renewed scrutiny of how boundary conditions are implemented for ultracold neutrons bouncing above a mirror in Earth's gravity. We apply the theory of self-adjoint extensions to the linear gravitational potential on the half-line and derive the most general boundary condition that renders the Hamiltonian self-adjoint. This introduces a single real self-adjoint parameter $λ$ that continuously interpolates between the Dirichlet case and more general (Robin-type) reflecting surfaces. Building on this framework, we provide analytical expressions for the energy spectrum, eigenfunctions, relevant matrix elements, and a set of sum rules valid for arbitrary $λ$. We show how nontrivial boundary conditions can bias measurements of $g$ and can mimic or mask putative short-range ''fifth-force''. Our results emphasize that enforcing self-adjointness-and modeling the correct boundary physics-is essential for quantitative predictions in gravitational quantum states. Beyond neutron quantum bounces, the approach is broadly applicable to systems where boundaries and self-adjointness govern the observable spectra and dynamics.

quant-ph↗

arXiv2023

Decoherence-Free Entropic Gravity for Dirac Fermion

The theory of entropic gravity conjectures that gravity emerges thermodynamically rather than being a fundamental force. One of the main criticisms of entropic gravity is that it would lead to quantum massive particles losing coherence in free fall, which is not observed experimentally. This criticism was refuted in [Phys. Rev. Res. 3, 033065 (2021)], where a nonrelativistic master equation modeling gravity as an open quantum system interaction demonstrated that in the strong coupling limit, coherence could be maintained and reproduce conventional free-fall dynamics. Moreover, the nonrelativistic master equation was shown to be fully compatible with the qBounce experiment for ultracold neutrons. Motivated by this, we extend these results to gravitationally accelerating Dirac fermions. We achieve this by using the Dirac equation in Rindler space and modeling entropic gravity as a thermal bath thus adopting the open quantum systems approach as well. We demonstrate that in the strong coupling limit, our entropic gravity model maintains quantum coherence for Dirac fermions. In addition, we demonstrate that spin is not affected by entropic gravity. We use the Foldy-Wouthysen transformation to demonstrate that it reduces to the nonrelativistic master equation, supporting the entropic gravity hypothesis for Dirac fermions. Also, we demonstrate how antigravity seemingly arises from the Dirac equation for free-falling antiparticles but use numerical simulations to show that this phenomenon originates from zitterbewegung thus not violating the equivalence principle.

quant-ph↗