Sat, January 1, 2011

Interaction?induced orbital excitation blockade of ultracold atoms in an optical lattice

Sat, January 1, 2011

Quantum simulation of antiferromagnetic spin chains in an optical lattice

Sat, January 1, 2011

Spin gradient demagnetization cooling of ultracold atoms

We have demonstrated a new cooling method in which a time-varying magnetic field gradient is applied to an ultracold spin mixture [1].  We prepare a two-component cloud of rubidium atoms, either in the superfluid or Mott insulator phase, in a strong field gradient separating the two components with a narrow mixed region between the pure-spin...

Sat, January 1, 2011

Quantum computing with light

Quantum computing with light

Sat, January 1, 2011

Speckle Imaging of Spin Fluctuations in a Strongly Interacting Fermi Gas

Spin fluctuations and density fluctuations are studied for a two-component gas of strongly interacting fermions along the BEC-BCS crossover [1].  Spin fluctuations are observed by directly measuring the difference in densities for the two spin states.  This was done by using a probe laser which had equal detuning from both states, but with opposite signs.

Fri, January 1, 2010

A Magnetic Gas

For decades, it has been an open question whether it is possible for a gas to show properties similar to a magnet made of iron or nickel.  Iron and nickel are ferromagnetic because they become strongly magnetized below a specific temperature, when unpaired electrons within the material spontaneously align in the same direction.

Fri, January 1, 2010

How to win a coin game called atomic clock

If you flip a hundred coins, you are unlikely to get exactly fifty heads and fifty tails; there is a statistical uncertainty in the outcome.  Researchers at MIT have reduced the statistical uncertainty in the quantum mechanical equivalent of a coin toss.  This quantum mechanical coin toss is more than a game: its uncertainty limits the precision of one of the world’s most sensitive measurement devices, the atomic clock.  An atomic clock consists of tens of thousands of atoms, each of which can be in either of two states, much like a coin that can show either of two faces.  Each atom is placed in a quantum superposition of the two states—each coin, as it were, suspended in mid-air with the potential to land on either face.  The researchers at MIT use light to probe an ensemble of such atoms in a way that allows them to count how many atoms are “heads” without revealing the state of any individual atom—without disturbing the superposition. Thereafter, the laws of quantum mechanics demand that the count remain the same on any subsequent measurement.  Thus, while each individual coin continues to tumble at random, the tumbling of the different coins is now choreographed: as one twists towards heads, another must turn towards tails.  In the jargon of quantum mechanics, the states of the different atoms are now entangled.  When one ultimately measures the states of the individual atoms—letting the coins land—the statistical uncertainty in the outcome is reduced.  Just such a measurement is used to read out an atomic clock; if the clock is operated in an entangled state, its precision is no longer at the mercy of an ordinary coin toss.

Fri, January 1, 2010

States of an Ensemble of Two-Level Atoms with Reduced Quantum Uncertainty

Fri, January 1, 2010

Coherent recoilless scattering of atoms

Two papers were finished recently on the subject of recoilless scattering from a gas and scattering from atoms in an optical lattice as a probe of the quantum state of the lattice.

Fri, January 1, 2010

Orientation-Dependent Entanglement Lifetime in a Squeezed Atomic Clock

Atomic Clock Beats the Quantum Limit