DeMarco Group Research

The DeMarco group focuses on using ultra-cold atom gases trapped in optical lattices to study models relevant to condensed matter physics. This techniques, of using one quantum system to study another, is called "quantum simulation." We are pursuing five primary research areas:

Studying frustrated quantum magnetism
Characterizing transport in the Bose-Hubbard model
Studying the the ground state phase diagram of the disordered Bose-Hubbard model
A mystery topic on the (Fermi) Hubbard model
Generating arbitarily-shaped potentials for atom gases, using either rf-dressing or holographic dipole traps

Particularly relevant journal articles on spin-based quantum simulation are quant-ph/0207011, Feynmann's original paper conjecturing quantum simulation, and Science 273, 1073 (1996). There is a brief list of bibliographical highlights on quantum simulation of quantum magnetism using ultra-cold atoms located at this link.

You can watch a video tour of our lab here (warning: 100 MB file).

Description of Research

Poster on disordered BH model (pdf link)

Poster on transport in the BH model (pdf link)

Poster on quantum magnetism in an optical lattice (pdf link)

Lab Space

The rennovations on our incredible lab space (approximately 1200 square feet) were finished in April 2004. We have a fantastic air handling system which provides stability at the 0.2 degree celsius level. We also are equipped with high pressure (150 psi) and high flow (15 gpm) closed-loop, temperature-regulated chilled water system. One of the neatest features of our lab space is the large fabric ducts which are used instead of diffusers; these ducts create laminar flow below 5 feet, even as the AHU changes out the lab air 40 times per hour.

Dec. 5,2003...Demolition begins.

April 2004...Rennovation is complete!

Apparatus

Vacuum System

Our vacuum system is pumped by 20 l/s and 40 l/s ion pumps and a titanium-sublimation pump. Magnetic trap lifetimes in the science cell are greater than 5 minutes. The glass cells were created by Ron Bihler / Technical Glass.

Our vacuum system

Science Cell

Collection Cell

Magnetic Trap

This unique trap will let us sneak optical lattice beams into our science cell in a geometry compatible with creating hyperfine state dependent potentials in three directions and simulataneously image with better than f/1 optics along five directions.

Click the thumbnails for a larger view.

Some Lab History

August 16, 2005... first observation of BEC!

On August 16, 2005, around 6 pm, we took our first pictures of a BEC of ⁸⁷Rb atoms. The BEC was formed in the |2,2> state with about 300,000 atoms at 150 nK. The animation below shows a sequence of absorption images taken after the magnetic trap is turned off and the gas freely expands for 26 ms. The sequence follows evaporative cooling from just above T_c to the point of making a nearly pure condensate. You'll see that the thermal gas appears to have circular symmetry, reflecting the isotropic momentum distribution of the gas in the magnetic trap. The condensate, however, is cigar shaped, revealing the anisotropic momentum spread of the ground state of the harmonic trap.

Young Scholar's Competition

On October 8, 2005, Brian took a first prize in the Young Scholars Competition at the Amazing Light symposium in honor of Charles Townes. This generous prize was sponsored by the Research Corporation. Brian's not as short as he looks in this photo...really.

Nov. 2006...first observation of superfluid-Mott insulator phase transition

We were able to see the superfluid to Mott insulator phase transition in an optical lattice for the first time on November 15, 2006. The data shown below were taken by ramping up a 3D optical lattice in 100 ms, holding for 5 ms, and then quickly shutting off. The last picture was taken after ramping up to 22E_R and then back down to 4E_R. Click on the picture for a larger view...