MICRA: status report Exploration of atom-surface forces on a micrometric scale via high sensitivity force measurements with ultracold quantum gases. Objectives:  new bounds on non-newtonian gravitational forces  investigation of Casimir-Polder forces Firenze (G. Modugno, M. Fattori, M. Inguscio, experiment) Trento (S. Stringari, A. Smerzi, theory) CSN II, Trento, September 26, 2013

The experiment principle A Bose-Einstein condensate with vanishing interaction in proximity of a source mass. Phase-oscillation of the interference pattern from e.g. a lattice potential M. Fattori et al., Phys. Rev. Lett. 100, (2008); M. Fattori et al., ibid.. 101, (2008).

Non-newtonian gravitational forces Our goal:  g = g  x = 2  m An analogous sensitivity is achievable with ultracold Sr atoms (G. Tino, Firenze): e.g. N. Poli et al. Phys. Rev. Lett. 106, (2011).

The metallic layer screens CP forces from the source masses. The insulating layer prevents atom adsorption. PRA 69, (2004) The masses are moved independently from the screen. The planned configuration 10  m 500  m 100  m Au (  =19.3,  =-28) Ag (  =10.5,  =-20)) 5  m Au MgF 2 Rb + - E → U G ~ 40 U G ’

Other methods Neutrons ( 1  m) No Casimir forces Torsion balances( >1-10  m) complex modelisation Microspheres ( 1  m) not yet realized in experiments

Activity : Experimental apparatus Science chamber (T < 100 nK) Magnetic trapping (T = 200  K) Laser cooling chamber Magnetic trap 39 K Bose-Einstein condensate Optical trap Sub-Doppler laser cooling of potassium atoms, M. Landini, et al., Phys. Rev. A 84, (2011). Direct evaporative cooling of 39K atoms to Bose-Einstein condensation, M. Landini et al., Phys. Rev. A 86, (2012). A new setup designed for high-precision interferometry with a BEC with tunable interaction

Activity 2012: Interaction control and 3-body processes Universality of the three-body Efimov parameter at narrow Feshbach resonances, S. Roy, et al.,Phys. Rev. Lett. 111, (2013). Control of the interactions in the atomic interferometer; interplay of two-body and three body processes (Efimov states)

Decoherence induced by the trapping potential 1 =1064 nm d = 1 /[2sin(  /2)] ~10  m 2 = 1 /2 = 532 nm Radial confinement An array of Mach-Zendher interferometers: common mode rejection of light shifts, vibrations, magnetic fields; interferometers array increases the sensitivity as. Activity : Double-well interferometers A test of the atomic interferometer is in progress, and will be presumably completed before the end of 2013.

Decoherence induced by the trapping potential Activity 2013: Light scattering from the surface? Strong decoherence in a lattice interferometer observed by N. Poli, G. Tino with Sr atoms. Light scattering from surface imperfections? High-resolution, ex-situ investigation of high quality surfaces during the next months.

Future activity on quantum interferometry Coherent states  shot noise limit Entangled states  Heisenberg limit Well-known ideas with e.g. photons, however not successfull so far with atoms, in the absence of interaction control. PI: Marco Fattori STREP, ERC Starting Grant, Futuro in ricerca 2009

Quantum enhanced sensitivity measurement beam splitter input phase shift Spatial Mach Zehnder Interferometer (non interacting particles) LR Uncorrelated particles Quantum entangled particles (interacting)  ~ 1/ (Shot noise limit)   ~1/N (Heisenberg limit) The present control of interaction can allow Heisenberg-limited sensitivity for the Micra measurements; potential extensions to general interferometric schemes, clocks, etc. Future activity on quantum interferometry PI: Marco Fattori STREP, ERC Starting Grant, Futuro in ricerca 2009

People and future activities Requested grant for 2014 Consumables: 4 keuro Firenze Giovanni Modugno Massimo Inguscio Chiara D'Errico, Ric TD CNR Trento Sandro Stringari Activity for 2014 Operation of the interferometer and generation of entangled states High-sensitivity, high-resolution measurements of gravitational and magnetic forces Experiment: Marco Fattori, ric. CNR Giacomo Spagnolli, PhD Giulia Semeghini, PhD Theory: Augusto Smerzi, ric. CNR Luca Pezzè, TD CNR