Questioning the Recent Observation of Quantum Hawking Radiation

Abstract

A recent article [J. Steinhauer, Nat. Phys. 2016, 12, 959] has reported the observation of quantum Hawking radiation and its entanglement in an analogue black hole. Here, the published evidence, its consistency with theoretical bounds, and the statistical significance of the results are analyzed. The analysis raises severe doubts on the observation of Hawking radiation.

Analogue Hawking radiation in an exactly solvable model of BEC

“…In the past years, Bose-Einstein condensates (BECs) were considered as possible candidates [6][7][8][9] and an experimental realization of a sonic black hole in a flowing BEC was first achieved few years ago [10]. More recently, two experiments [11,12] made a considerable progress towards the direct observation of Hawking radiation in a quasi-one-dimensional set-up but the complete characterization of the observed phenomena is still under debate [13][14][15][16][17][18]. In Bose-Einstein condensates this mechanism has always been studied within semiclassical approximation via the Gross-Pitaevskii equation supplemented by a Bogoliubov analysis of the excitation spectrum (see, for instance, [4,[19][20][21][22]), while a seminal investigation in Fermi gases related the phonon emission at the sonic horizon to the quantum reflection against a potential barrier [23].…”

Comment on “Questioning the Recent Observation of Quantum Hawking Radiation” [Ann. Phys. (Berlin) 2018, 530, 1700114]

“…We will see that ref. [] has modified the experimental data before using it to compute the theoretical bound which limits the correlations. The modification results in an apparent violation of the theoretical bound.…”

“…Based on this misquotation, ref. [] artificially removes the contribution due to the finite space, as seen in Figure . The experimentally‐measured widths are shown in the left panel of Figure .…”

“…Several theoretical works discussed the observation . In addition, a Comment was presented . This paper responds to the third version, which was published as an article .…”

“…In addition, a Comment was presented . This paper responds to the third version, which was published as an article . The article contains some technical difficulties, including the misunderstanding of a simple Fourier transform, the unnecessary modification of experimental data, and the assertion that the experiment measured a strictly‐zero population.…”