Correlated phonon pairs in a time modulated Bose-Einstein condensate
Résumé
In standard cosmological models, inflation is driven by a quantum field, the inflaton, whos constant energy density drove the superluminal expansion of the universe [1]. When inflation stops, the universe has an extremely low density btu the inflaton field starts to oscillate arround its minimum of energy and decays into entengled pairs of particles [2], known as the pre-heating phase. Created pairs of particles then start to interact leading to decoherence and thermalization : the re-heating stage. If in situ observation of inflaton particle creation process is impossible, this pair production through parametric amplification is analogous to the creation of phonon pairs in a Bose-Einstein (BEC) condensate whose interaction strenght is time modulated. Modulating the stiffness of a dipole trap of a cigar-shape BEC being equivalent to modulate the effective one-dimensionnal interaction strenght in a BEC, we are able to probe the correlation of entengled metastable helium atoms by the use of a micro-channel plate detector (MCP). Our experimental procedure is the following [3] : we modulate in time the trap stiffness of the dipole trap laser and then release the trap (see figure 1). During expansion, the phonon kinetic energy is adiabatically transferred to one atom that is detected by the MCP after a 300 ms time of flight. The amount of created phonon pairs is expected to depend on the duration of the excitation, its amplitude and the excitation frequency. However, the region in which the entenglement of the phonon pairs can be observed is expected to be quite narrow [4]. We propose to investigate the entenglement and correlations of those pairs of particles. [1] L. Kofman, A. Linde, and A. Starobinsky, Phys. Rev. D 56, 3258 (1997). [2] D. Campo and R. Parentani, Phys. Rev. D 74, 025001 (2006). [3] S. Robertson, F. Michel, and R. Parentani, Phys. Rev. D 95, 065020 (2017). [4] J.-C. Jaskula et al., Phys. Rev. Lett. 109, 220401 (2012).