Fichas
Quantum optics Set 3
Fichas del conjunto (15)
- 1BEC with attractive interactions- scattering length a <0 → negative cooling (collapse sketch)
- But zero point energy (Quantum pressure)→ stabilization - 2BEC-Dispersionrelationweakly interacting BEC: hν=E(k)=√(ħω_k^0 (ħω_k^0+2μ))
Phononen-Limit: hν0<<2μ → E(k)=p√(c_s )
Particle limit: E(k)≈hν_0+hΔν
measure dispersion by scattering - 3BEC-Superfluiditymovement without resistance
v>vc → scattering
vc_s;E(p ⃗ )/p ⃗ =c_s - 4BEC in optical lattices- fluctuating atom number, well defined phase relation
- interference pattern - 5Thomas-Fermi-Limitneglect kinetic term in GPE
Vext is harmonic
size of BEC: R_TF=an_0 ((15N_a)/(an_0 ))^(1/5) - 6Scattering length- appears in atomic cross section
- determined by binding energy of last bound vibrational state
- positive or negative
- determines (non-)attractive BEC
- tunable by feshbach resonances - 7Vorticies in a BECmacroscopic condensate wave function
quantized circulation
in order to fulfill angular momentum criteria the wavefunction vanishes in the „eye of the vortex“ because there it should rotate infinitely fast - 8Principle of Atom Interferometry- splitting of a wave (function) into two ways
- Phase shift inbetween the two ways →different probabilities→ interference
- Measure:
o gravitation
o rotations
o fundamental physical constants
o atomic properties (atomic polarizability) - 9Mach-Zehnder Interferometer- phase shift at BS2: π
- 10Interfering BECpreparation of a BEC in a magnetic trap
splitting the BEC with a laser (blue detuned)
release both parts of the BEC
|ψ(t)|^2=|ψ_A^* (t) ψ_B (t)|^2
one gets an interference pattern with: δ_2π==λ_(dB,rel) - 11Diffraction by grating3 gating
Δ_detector=Δ_geom+Δ_int=Φ_A =Φ_B - 12adiabatic followingwhen does a moving atomic moment keep it's orientation relative to magnetic field?
ω_Larmor=(gm_F μ_B)/ħ |B|
ω_rot≪ω_Larmor
at B=0: atom does not know how to orientate → half is lost - 13Quadrupole and Ioffe-Pritchard Trap- Quadrupole:
o pair of coils in anti „helmholtz“ configuration
o low-field seekers can turn into high field seekers
- Ioffe-Pritchard Trap
o Main adavantage: No majorana losses - 14Optical pumping- transfer the atom with σ+ or σ- light into a desired other mF state
- 15Dark states- state , which does not change under the influence of light
- cannot absorb an incident photon
- for cooling:
o no population in excited state
o destructive interference of excitation amplitudes
o coherent superpositions
Información
- Descripción
- El usuario ha eliminado su información de asignaturas Fichas sobre Quantum optics Set 3, creado por Usuario eliminado el 24/09/2017.
- Creado por
- Usuario eliminado · sep 2017
- Actualizado
- 24 sep 2017
- Visitas
- 20
- Historial
-
- Creado por Tom Schobert · 21 sep 2017
- Copiado por Tom Schobert · 24 sep 2017
- Valoración