Dipole-dipole interactions in Rydberg states

Outline Strontium experiment overview Routes to blockade Dipole-dipole effects

Team strontium Matt JonesCharles Adams MeDan Sadler Danielle Boddy Christophe Vaillant

Rydberg physics Rydberg atoms: States of high principal n Strong, tunable interactions Position Column density Excited state Ground state

Spatial measurements Automatic translation state Lens setup

Autoionization 5s 2 5s5p 5sns(d) 5s Sr + 5pns(d) λ 1 = 461 nm λ 2 = 413 nm λ 3 = 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 Probe + Coupling (1 μs) 408 pulse (1 μs) Electric field pulse (5 μs) ~10 6 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 5s 2 1 S 0 5s5p 1 P 1 5s4d 1 D 2 5s6s 3 S 1 5s5p 3P23P2 3P13P1 3P03P0 461 nm 679 nm707 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, (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 m J 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  m J projection good Internuclear axis not aligned with quantization axis  m J 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