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, Trieste, September 19, 2012

The experiment principle A Bose-Einstein condensate with tunable 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)

Gravitational vs Casimir-Polder force 10  m 500  m 100  m e.g. Au:  =19.3 Force budget: F g = mg = 10 9 Hz/m F CP = 10 5 Hz/m F G = dU G /dr = 50 Hz/m Expected sensitivity (1s, 100 measurements):  F = F g (100 Hz/m)) van der Waals Casimir-Polder thermal (Lifshitz)

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

2012: new set-up for interferometry Science chamber (T < 100 nK) Magnetic trapping (T = 200  K) Laser cooling chamber high magnetic field stability high resolution imaging (1  m) single species approach large repetition rate (5 Hz)

2012: the Bose-Einstein condensates Magnetic trap Magnetic Feshbach field Optical trap (2mK  1  K) M. Landini, S. Roy, L. Carcagnì, D. Trypogeorgos, M. Fattori, M. Inguscio, G. Modugno, Phys. Rev. A 84, (2011); M. Landini et al. submitted (2012).

2012: interaction control and 3-body resonances Important interplay of 2-body and 3-body (Efimov) physics. M. Zaccanti et al., Nature Physics 5, 586 (2009) Universal behavior of atomic Efimov states

Towards quantum interferometry with BECs Coherent states  shot noise limit Entangled states  Heisenberg limit Dynamic control of the interactions: entangled states larger than in other any system are in principle possible.

Quantum enhanced sensitivity measurement beam splitter input phase shift Spatial Mach Zender Interferometer (non interacting particles) LR Uncorrelated particles Quantum entangled particles (interacting)  ~ 1/ (Shot noise limit)   ~ 1/N (Heisenberg limit) Appel, J. et al. Proc. Natl Acad. Sci. USA 106, (2009); C. Gross, T. Zibold, E. Nicklas, J. Estève, M. K. Oberthaler, Nature 464, 1165 (2010); Pezze´, L. & Smerzi, A., Phys. Rev. Lett. 102, (2009). Tunability !!! Direct applications to high-sensitivity measurements; potential extensions to other interferometric schemes, clocks, etc. Quantum-enhanced sensitivity

Decoherence induced by the trapping potential 1 =1064 nm d = 1 /[2sin(  /2)]~ 10  m 2 = 1 /2 = 532 nm Lattice: common mode rejection of light shifts in the wells Array of interferometers: rejection of uncontrolled spurious forces (vibrations, magnetic field gradients, etc…) Radial confinement J. Sebby-Strabley, et al., Phys. Rev. A 73, Super-Lattice Array of interferometers: increase of the sensitivity, with M the number of intererometers. 2012: array of double-well interferometers

2012: ex-situ realization of the superlattice

People and future activities Requested grant for 2012 Consumables: 4 keuro Firenze Giovanni Modugno Massimo Inguscio Chiara D'Errico, Ricercatrice TD CNR Luca Tanzi, dottorando Trento Sandro Stringari Activity for 2013 Calibration of the interferometer and generation of entangled states June 2013: High sensitivity force measurements on short distances Experiment: Marco Fattori, ric. CNR Manuele Landini, TD CNR Andreas Trenkwalder, TD CNR Theory: Augusto Smerzi, ric. CNR Luca Pezzè, TD CNR STREP, ERC Starting Grant, FIRB – Futuro in ricerca 2009

Experimental apparatus 2D Mot 3D Mot Science chamber

Out of equilibrium CP force The CP force can in princple be reduced by reducing the surface temperature

Laser cooling: new discoveries from an old method  Sub-Doppler laser cooling of potassium was considered impossible because of the narrow hyperfine structure.  A new strategy based on dark states allows to achieve temperatures not far from the most gifted species (e.g. rubidium)  New prospects for a test of the equivalence principle? (MAGIA setup) 39 K 41 K M. Landini et al., submitted

Sub Doppler cooling  The narrow hf structure disturbs the cooling cycle  The dark ground hf state is used to control the photom scattering rate, to reduce heating  Cooling at large densities is possible