title: Quantum Enhancement of the Index of Refraction in a Bose-Einstein Condensate.
abstract: We study the index of refraction of an ultracold bosonic gas in the dilute regime. Using phase-contrast imaging with light detuned from resonance by several tens of linewidths, we image a single cloud of ultracold atoms for 100 consecutive shots, which enables the study of the scattering rate as a function of temperature and density using only a single cloud. We observe that the scattering rate is increased below the critical temperature for Bose-Einstein condensation by a factor of 3 compared to the single-atom scattering rate. We show that current atom-light interaction models to second order of the density show a similar increase, where the magnitude of the effect depends on the model that is used to calculate the pair-correlation function. This confirms that the effect of quantum statistics on the index of refraction is dominant in this regime.
authors.affiliation: Nanophotonics, Debye Institute, Center for Extreme Matter and Emergent Phenomena, Utrecht University, P.O. Box 80,000, 3508 TA Utrecht, The Netherlands.
authors.forename: P C
authors.initials: PC
authors.lastname: Bons
authors.affiliation: Nanophotonics, Debye Institute, Center for Extreme Matter and Emergent Phenomena, Utrecht University, P.O. Box 80,000, 3508 TA Utrecht, The Netherlands.
authors.forename: R
authors.initials: R
authors.lastname: de Haas
authors.affiliation: Nanophotonics, Debye Institute, Center for Extreme Matter and Emergent Phenomena, Utrecht University, P.O. Box 80,000, 3508 TA Utrecht, The Netherlands.
authors.forename: D
authors.initials: D
authors.lastname: de Jong
authors.affiliation: Nanophotonics, Debye Institute, Center for Extreme Matter and Emergent Phenomena, Utrecht University, P.O. Box 80,000, 3508 TA Utrecht, The Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: Groot
authors.affiliation: Nanophotonics, Debye Institute, Center for Extreme Matter and Emergent Phenomena, Utrecht University, P.O. Box 80,000, 3508 TA Utrecht, The Netherlands.
authors.forename: P
authors.initials: P
authors.lastname: van der Straten