Dipole-dipole interactions in Rydberg states
Outline
• Strontium experiment overview
• Routes to blockade
• Dipole-dipole effects
Team strontium
Matt Jones Charles Adams
Me Dan Sadler
DanielleBoddy
ChristopheVaillant
Rydberg physics
Rydberg atoms:
• States of high principal n
• Strong, tunable interactions
Position
Co
lum
nd
en
sity
Excited state
Ground state
Spatial measurements
Automatictranslation state
Lens setup
Autoionization
5s2
5s5p
5sns(d)5s Sr+
5pns(d)
λ1 = 461 nm
λ2 = 413 nm
λ3 = 408 nm• Resonant ionization process
• Increases signal over spontaneous ionization
• Independent excitation and detection
• Can give spectral and temporal information
Preliminary results
Time
Repeat
MOT + Zeeman
MOT + Zeeman
Probe +
Coupling
(1 μs)
408
pulse
(1 μs)
Electric
field pulse
(5 μs)
• ~106 atoms at 5 mK• Camera image for atom number• 408 is focused to 10 μm• Translation stage stepped• Ions detected on an MCP
Increasing density
5s2 1S0
5s5p 1P1
5s4d 1D2
5s6s 3S1
5s5p
3P2
3P1
3P0
461 nm
679 nm 707 nm
Current cooling scheme has leak
Repumping increases density by approximately an order of magnitude
Förster zeros
T.G. Walker and M. Saffman, PRA 77, 032723 (2008)
Long range van der Waals interaction couples pairs of states
: radial part of the interaction
: angular part of the interaction
Förster zero is where is zero
Sum over all final states to get total interaction
Quantization coils I
Apply magnetic field to define quantization axis
Polarization well defined, can excite specific mJ
Need to switch fast
Avoid losing density
External coils too slow
Eddy currents in chamber
Quantization coils II
Solution: Use internal coils
Vertical excitation beams are orthogonal to autoionizing beam
Internuclear axis
Internuclear axis aligned with quantization axis
mJ projection good
Internuclear axis not aligned with quantization axis
mJ projection varies
Solution: Use S states or make geometry 1D
Summary
• Signal to noise of spatial measurements is good
• Close to blockade densities
• Need to control polarization to avoid Förster zeros