We are atom coolers in Aephraim Steinberg's research group. We trap and Cool Rubidium 85 atoms using the usual MOT-molasses method in a vapor cell and perform various experiments on them. The other experimentors on these projects are graduate student Samansa Maneshi and our post-doc Matt Partlow.

We have other experiments and other grad students in the lab, but I try not to let that bother me. They are:
Jeff Lundeen
Mirco Siercke
Chris Ellenor
Rob Adamson
Krister Shalm
Fan Wang

The Quantum Delta Kicked Rotor with Cold Atoms

The classical delta-kicked rotor (DKR) exhibits chaotic behaviour in certain parameter regimes, characterized by a linear increase of the energy of the system as a function of time. Applying the DKR to a quantum system, however, will eventually result in states that are localized in momentum space. Therefore, the delta kicks can only increase the energy of the system up to a finite limit given by the momentum localization length. Recent extensions of the quantum DKR by P. Brumer and J.Gong predict coherent control of the relaxation of the system into the localized eigenstates through manipulation of the coherence properties of the initial state and spatial phase of the pulsed potential. This can result in either a further suppression of diffusion or superheating in which the system absorbs energy faster than classically  allowed

Quantum Error Correction

Our optical lattice can be tailored to support only two bound states. Phase modulation of the lattice can create various superpositions of the two bound states, known in the quantum information world as a qubit. Because of imperfections in the sinusoidal potential these qubits undergo dephasing and decoherence. Further phase (and/or intensity) modulations can correct for these dephasing mechanisms. We are studying techniques to preserve the coherence of our qubits not just in the face of our dephasing mechanisms, but to realize a generalized technique through optimization algorithms to find correction schemes for a range of dephasing/decoherence mechanisms.

Quantum Process Tomography of an Optical Lattice System

By subjecting four known independant states to an unknown time-dependant potential and subsequently measuring the output density matirces one can construct the SuperOperator of the potential. This operator fully characterizes the system and predicts the output state for any given input state. We reconstruct this superoperator for various processes in an optical lattice. Processes measured include resonant shaking of the lattice, instantaneous shifts of the lattice and what should be the Identity (doing nothing to the lattice) but isn't because of dephasing/decoherence mechanisms.

Quantum Tomography of Atoms in an Optical Lattice

The individual wells of a 1-D optical lattice can be approximated by a harmonic potential. We have mapped the motional density operator of atoms in this potential in the number state basis. The same theory for tomography for photonic states is applicable here. What we actually measure is the quasi-probability distribution known as the Husimi, or Q, distribution. It is always real and positive, thus measurable in the laboratory. However, it still has all the information as the Wigner distribution or the density operator.

Velocity Selection of Atoms in a Magnetic Trap

Atoms are trapped in a weak quadrupole magnetic trap, and a blue-detuned laser sheet is placed to the side of the trap. The magnetic trap is then moved past the laser sheet. The repulsive potential due to the blue-detuned laser prevents the colder atoms (those with less kinetic energy than the laser potential) from moving past it, separating them from the more energetic atoms which can classically overcome this potential. The result is a cold sample of atoms spatially separated from the original atom cloud.

Magnetic Field Delta Kick Cooling

By application of a pulsed magnetic field, laser-cooled Rb atoms are cooled in one dimension, by a factor of 10 below the temperature of optical molasses. While phase-space density is conserved in this process, the method is more efficient than adiabatic expansion. We have achieved temperatures below 700 nK, but there is no fundamental limit to this cooling technique. The technique can also be used as an atom lens and as a spin-dependent probe.