DS10 - Défi de tous les savoirs

Hawking Radiation in the Lab – HARALAB

Submission summary

We propose to study the radiation emitted by analogue black holes in two different systems: in a water tank, and in an atomic Bose-Einstein condensate (BEC). In the first case, the radiation consists of surface waves propagating against the flow, whereas in the second one, sound waves (phonons) propagate in a flowing condensate. The experiments we plan are highly complementary. The former will operate in the stimulated, i.e. classical, regime. Namely, we shall observe the scattering of waves sent by a wave generator against a counter flow. These waves are blocked when the flow speed becomes trans-critical. To unravel the Hawking effect, we shall measure the amplitude of the negative energy wave which is emitted when the incident wave is blocked. The main novelty here is that we will work with flows which can be both trans-critical and regular. Although this situation has never been realized, it is a prerequisite in order for the scattering of surface waves to constitute a close analogy with the scattering responsible for the Hawking effect taking place near the horizon of a black hole. Another novelty will consist in comparing the data with detailed numerical simulations of the scattering of surface waves in such flows.

In atomic gases, we will work to reach sufficiently low temperatures so as to be able to observe the spontaneous production of phonon pairs induced by the amplification of vacuum fluctuations. In this regime, pair production gives rise to quantum mechanically entangled states. To be able to distinguish these states from those obtained by the amplification of thermal fluctuations, we will measure the relative intensity of the correlations bewteen the two types of phonons involved in the pair production. In a first step, to validate these new techniques involving violation of Cauchy-Schwartz inequalities, we shall study the dynamical Casimir effect which is simpler to realize, but which is conceptually very close to the Hawking effect in that it also rests on the production of pairs of correlated phonons. In a second step, we shall try to apply the same techniques to phonon pairs emitted by the Hawking effect.

The conception, the implementation, and the analysis of these experiments will be done in close collaboration with the two theoretical teams. The theoreticians will be particularly involved in precise (numerical) calculations of the spectral properties of the fluxes, so as to identify the optimal regimes to conduct the experiments. They will be also involved in the calculation of the intensity of the correlations among partner modes in the produced pairs. This is necessary to identify the narrow domains in parameters space where Cauchy-Schwarz inequalities are violated. Finally the theoreticians will be involved in the conception of the obstacles giving rise to regular trans-critical flows, something involving non-linear hydrodynamical effects which have not yet been taken into existing analogue gravity studies.

Project coordination

Christoph Westbrook (Laboratoire Charles Fabry)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

IOGS- LCF Laboratoire Charles Fabry
LPT Laboratoire de Physique Théorique
LPTMS Laboratoire de Physique Théorique et modèles Statistiques
Pprime Institut Pprime

Help of the ANR 349,960 euros
Beginning and duration of the scientific project: September 2015 - 36 Months

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