Experimental Quantum Physics The starting point Level 0.1: We want to - - PDF document
Experimental Quantum Physics The starting point Level 0.1: We want to have fun with experimental quantum mechanics and gain as much control as possible over the processes Level 1.0: Do something useful with the systems: e.g
The starting point
Level 0.1: We want to have fun with experimental quantum mechanics… … and gain as much control as possible over the processes Level 1.0: Do something “useful” with the systems: e.g Quantumsimulation “complex” q.m. system time evolution with H “simple” model system mapping time evolution with H’ mapping
There are various ways to generate that, we will only consider neutral atoms
One of the main ingredients of the quantum laboratory
T>>Tc T~Tc T=0
d v dB
Bose Einstein Condensate
mechanical level
matter wave interference
ground state as well as dynamical behavior
Some properties of BEC
experimental parameters
Theoretical prediction 1924/5: A. Einstein and S. N. Bose First experimental realization 1995 BEC in dilute alkali gases: E. A. Cornell, W. Ketterle and C. E. Wieman
Experimental realization of BEC
2D‐MOT 3D‐MOT Molasses
Magnetic trap Evaporation
n=104cm‐3 T=300K
n=1010cm‐3 T=10‐100µK n=1014cm‐3 T=100nK
Laser cooling
Experimental realization of BEC
n=104cm‐3 T=300K
n=1010cm‐3 T=10‐100µK n=1014cm‐3 T=100nK
Laser cooling
2D‐MOT 3D‐MOT Molasses
Magnetic trap Evaporation
2D‐MOT 3D‐MOT Molasses
Magnetic trap Evaporation
Dipol trap n=104cm‐3 T=300K
n=1010cm‐3 T=10‐100µK
n=1014cm‐3 T=100nK n=1014cm‐3 T=100nK
Particle number from 1010 down to 106
Experimental realization of BEC
2D‐MOT 3D‐MOT Molasses Magnetic trap Evaporation
Dipole trap
n=104cm‐3 T=300K n=1010cm‐3 T=10‐100µK
n=1014cm‐3 T=100nK
Isotropic trap Elongated trap
Experimental realization of BEC
2D‐MOT 3D‐MOT Molasses
Magnetic trap Evaporation
n=104cm‐3 T=300K
n=1010cm‐3 T=10‐100µK
n=1014cm‐3 T=100nK n=1014cm‐3 T=100nK
Particle number from 1010 down to 106
Experimental realization of BEC One, two,…more…
Degenerate Bose gas Exploiting the different quantum statistics Degenerate Fermi gas Various combinations:
components
Physics with Bose‐Einstein condensates
Bloch, Munich
Atom Laser
Ketterle, MIT
Collective excitations
Greiner, MPQ
Optical lattices Molecular BEC
Grimm, Innsbruck
Multi component BEC
Hamburg
Low‐dimensional systems
Paredes, MPQ
BEC
Ok, so we have a fancy quantum mechanical system with quite some control, but what to simulate with it?
Non‐exclusive choice of applications
Motivation and Applications
can be realized using interfering laser beams
parameters
Benefits of OL
Back to some basic atomic physics
Light
electric dipole transitions Transition matrix element Coupling of the two systems leads to a shift of the energy levels The shift is proportional to ∆~ ∙
~
In words: The (potential) energy of the respective atomic level depends on the intensity distribution of the light field Atom
| | | |, ,
Atoms in an off‐resonant laser beam
Neutral Atom Time dependent electric field
Induced dipole moment Induced dipole moment interacts with the electric field Force onto the atom
Periodic potentials
Simplest case: 1D lattice by retro reflecting a laser beam Optical dipole potential:
intensity distribution of the light field
laser (usually “‐“)
Optical lattices: Light crystals
Laser Laser Optical lattice : laser interference Potential for polarizable atoms Lattice beam intensity (lattice depth) Tunnel rate Optical lattices:
Interactions Periodic potential Solid: ionic crystal Potential for electrons Band structure
16
Ways to measure what‘s going on
Direct site resolved imaging Weiss, Greiner, Bloch and other labs Ott lab Imaging after release from lattice
Resonant Imaging Beam
CCD camera
Laser Laser
In‐situ momentum distribution is converted into real space due to free expansion
Tuneable lattice geometries
Most simple case: make the mutually orthogonal sets of beams independent V x, y, z ~
, cos , cos , cos
Greiner et al.
Dimensionality and Geometry
Kagomé Honeycomb Triangular
Jo et al.,Phys. Rev. Lett. 108, 045305 (2012) Soltan‐Panahi et al., Nature Physics 7, 434 (2011) Tarruell et al., Nature 483, 302 (2012) Becker et al., New J. Phys. 12, 065025 (2010) Overview on novel geometries: Windpassinger & Sengstock
Toolbox of tunable lattice geometries
Double well lattices Variable geometries
e.g. J. Porto (NIST),
(Hamburg)
Windpassinger & Sengstock