Abstract

Just a few atoms: Imaging for Matter-Waves Optics M. Pappa,1 P.C. Condylis,1 M. Baker,1 D. Sahagun Sanchez,1 A. Lazoudis,1 G. Konstantinidis,1 O. Morizot,1 and W. von Klitzing1,  1IESL{FORTH Institute of Electronic Structure and Lasers, Foundation of Research and Technology – Hellas, GR711 10 , Heraklion Crete, Greece Tel +30-2810-39-1546 Interferometry with massive particles oers an enormous increase in sensitivity and accuracy both for fundamental and applied physics. One of the key aspects is the fact that the number of massive particles are preserved throughout the experiment. This can be exploited, for example, in Heisenberg limited detection, where the sensitivity scales with the number of particle as opposed to its square root. It would therefore be of great interest to be able to image low atom numbers at the atom shot-noise limit with good spatial resolution. Fluorescence imaging oers single particle sensitivity¹ but usually requires the atom to be conned in a trapping potential. Recently, this technique has been extended to images of atoms falling through a sheet of light.[2] Multichannel plates can be employed to detect single metastable atoms falling upon it.[3] However, a imaging technique which works in free-space has single-particle sensitivity is yet to be demonstrated. Traditional absorption imaging oers very good resolution and easy of use. Unfortunately, due to technical noise it rarely reaches shot-noise limited performance. In this talk I will review the limits of traditional absorption imaging and then demonstrate diractive dark ground imaging as an ultra-sensitive imaging technique capable imaging atomic ensembles of tens of atoms with Fourier-limited spatial resolution. We demonstrate an improvement by an order of magnitude in sensitivity, when compared to absorption imaging, or time-resolution when compared to u- orescence imaging. Finally, we will address the limits of coherent imaging, where the atom shot-noise approaches unity. FIG . 1: Dark-ground image of a two component spinor BEC of 28 atoms after Stern-Gerlach separation into its dierent magnetic hyperne states. From left to right: about 7 atoms in the the hf = 2;mf = 􀀀2i state, 23 atoms in the hf = 2;mf = 􀀀1i state, and 34 atoms in the hf = 2;mf = 0i state. The other states are not populated. The clouds have a 1=e2 radius of 5:7  4:2m. The exposure time was 200 s: [1] Localized visible Ba+ mono-ion oscillator,W. Neuhauser, M. Hohenstatt, P. E. Toschek, and H. Dehmelt , Physical Review A (1980). [2] Single-particle-sensitive imaging of freely propagating ultracold atoms, R. Bucker, A. Perrin, S. Manz, T. Betz, C. Koller, T. Plisson, J. Rottmann, T. Schumm, and J. Schmiedmayer , New Journal of Physics (2011). [3] Hanbury Brown Twiss eect for ultracold quantum gases, M. Schellekens, R. Hoppeler, A. Perrin, J. V. Gomes, D. Boiron, A. Aspect, and C. I. Westbrook, Science (2005). Electronic address: wvk@bec.gr; URL : http://www.bec.gr