Single atom manipulations Beno

1
Single atom manipulationsBenoît Darquié, Silvia
Bergamini, Junxiang Zhang, Antoine Browaeys and
Philippe Grangier

• Laboratoire Charles Fabry de l'Institut d'Optique
  Théorique et Appliquée
• UMR 8501 du CNRS
• 91 403 Orsay

http//www.iota.u-psud.fr/grangier/Quantum_optics
.html
2
Introduction

• Experience
• Context
• Goals

study and manipulation of an optical dipole trap
for single atoms

• two neutral atoms
• trapped in two different dipole traps
• confinement ? mm3
• a few microns away from one another

• entangle the atoms
• make a quantum gate

3
Principle of a dipole trap
Assumption two-level atom, in a laser-field of
frequency wL, with a red detuning d wL - w0 lt
0.
two-level atom
Atoms are trapped in the high intensity regions Th
e transition frequency is shifted to the blue
4
Dipole trap
Dipole force non-dissipative forcegt we
previously have to cool atoms
5
The microscope objective MIGOU

• Characteristics of MIGOU
• large numerical aperture 0,7
• diffraction limited spot
• large working distance (1cm)
• ultra high vacuum compatible

• Double use of MIGOU
• to secure the focussing of the trapping beam in
  the center of the MOT
• to collect the fluorescence of trapped atoms
  with a large efficiency

6
Experimental set-up
7
Pictures of the dipole trap on the CCD camera

• Continuous observation of the fluorescence of
  the
• dipole trap on the CCD caméra.
• One picture every 200 ms.

Fluorescence
Fluorescence (CCD)
10 000 counts (200 ms)
Y
scaling of imaging system 1 pixel 1 mm
X
8
Single atom regime
9
Double trap
In single atom regime, there are four likely
configurations
10
Temperature of the atoms and trap frequencies

• Goals
• Requirements

• entangle the atoms
• make a quantum gate

• atom in the Lambe-Dicke regime h ltlt 1

we have to measure the temperature of the atoms
and the trap frequencies
11
Oscillation frequencies principle of the
measurement

• We trap one atom.
• We switch off and on the dipole trap during Dt1.
• ? If the atom is recaptured, it starts to
  oscillate in the trap.
• We wait for Dt and then, we switch off and on
  the dipole trap during Dt2.
• ? P(Dt) is the probability to recapture the atom
  after the whole sequence.

Dipole trap
Dt1
Dt2
ON
Dt
OFF
? oscillate at 2fosc.
12
Oscillation frequencies experimental results
Ptrap 1,9 mW
Ptrap 1,5 mW
Delay (ms)
Dt1 2.5 ms
Dt1 1 ms
13
Temperature of the atom time of flight
experiments

• Time sequence

14
Temperature of the atom time of flight
experiments

• Time sequence

1 We trap one atom
2 We switch off the MOT
15
Temperature of the atom time of flight
experiments

• Time sequence

1 We trap one atom
2 We switch off the MOT
3 The trapping beam is switched off
during Dt
? We measure the probability of recapturing the
atom after Dt.
16
Temperature of the atom results
T 35 mK
17
Conclusion and outlooks

• We are now able to evaluate the trap frequencies
  and the temperature of the atoms
• We need
• a better confinement
• a smaller temperature
• Better confinement ? retro-reflexion of the
  trapping beam, standing wave
• Smaller temperatures ? Raman cooling

Lamb-Dicke parameters ?r ? 0.5 ?z ?
2.5
18
Single atom manipulationsBenoît Darquié, Silvia
Bergamini, Junxiang Zhang, Antoine Browaeys and
Philippe Grangier
Laboratoire Charles Fabry de l'Institut d'Optique
Théorique et Appliquée UMR 8501 du CNRS 91 403
Orsay
http//www.iota.u-psud.fr/grangier/Quantum_optics
.html
19
Entanglement of two atoms
Atome 1
Atome 2
beam splitter
detector of p-polarized light
20
Entanglement of two atoms
Excitation by a photon of the probe beam
detection of s-polarized ligt
detection of p-polarized light
atoms behave as Young's slits ? interferences
projection onto the state
? entanglement
21
Plan of my talk

• Principle of the optical dipole trap
• Implementing a dipole trap A microscope
  objective MIGOU Experimental set-up
  Pictures of the dipole trap Double dipole trap
• Temperature of the atoms
• Oscillation frequencies of the dipole trap
• Conclusion and outlooks