News: Research Highlights

Sat January 1, 2011

Evolution of Fermion Pairing from Three to Two Dimensions

Interacting fermions in coupled two-dimensional (2D) layers present unique physical phenomena and are central to the description of unconventional superconductivity in high-transition-temperature cuprates and layered organic conductors. Reduced dimensionality enhances the effect of fluctuations, while interlayer coupling can stabilize superconductivity and even amplify the transition temperature. A fermionic superfluid loaded into a periodic potential should...
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Research Highlights
Sat January 1, 2011

Relaxation of Fermionic Excitations in a Strongly Attractive Fermi Gas in an Optical Lattice, Phys. Rev. Lett., 107 145303 (2011).

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Sat January 1, 2011

Revealing the Superfluid Lambda Transition in the Unviersal Thermodynamics of a Unitary Fermi Gas

Fermi gases, collections of fermions such as neutrons and electrons, are found throughout nature, from solids to neutron stars. Interacting Fermi gases can form a superfluid or, for charged fermions, a superconductor. We have directly observed the superfluid phase transition in a strongly interacting Fermi gas via high-precision measurements of the local compressibility, density and...
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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.

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Research Highlights
Fri January 1, 2010

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

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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.
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Fri January 1, 2010

Orientation-Dependent Entanglement Lifetime in a Squeezed Atomic Clock

Atomic Clock Beats the Quantum Limit

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Fri January 1, 2010

Probing quantum phase transitions at the single-atom level

Physicists Get an Up–Close Look at Synthetic Quantum Materials

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Research Highlights
Fri January 1, 2010

Probing the Superfluid?to?Mott Insulator Transition at the Single-Atom Level

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Research Highlights
Fri January 1, 2010

Rare-earth Atom Collisional Anisotropy

 
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Research Highlights