Sat, January 1, 2011

A cryogenic beam of refractory, chemically reactive molecules with expansion cooling

Atomic and molecular beams have been valuable tools for precision measurement of atomic and molecular spectra for the past several decades.  In order to achieve good signal to noise in a beam spectroscopy experiment, it is important to have high fluxes, low forward velocity (to increase interaction time), and, in the case of molecules, cold...

Sat, January 1, 2011

A Cold and Slow Molecular Beam

Due to the rich internal structures and the long range, anisotropic, and tunable interaction of polar molecules, increasingly efforts have been devoted to producing cold polar molecules for studying quantum simulation, cold, controlled chemistry, and precision measurements. We reported producing a cold, slow calcium monohydride molecular beam using a two-stage cryogenic buffer gas cell. This...

Sat, January 1, 2011

Low-inelastic-rate Atom-Molecule Collisions in a Magnetic Trap

The study of low-temperature molecular collisions is a key step to understanding the fundamental processes in archetypal few-body systems, but also as a stepping stone to further cooling, whether sympathetic or evaporative. With the aim of building on our buffer-gas-loaded BEC work with metastable helium, we studied, both theoretically and experimentally, the collisional properties of...

Sat, January 1, 2011

Making Van Der Waals Molecules

Van der waals molecules involving helium as a partner are typically very weakly bound and exist only in non-equilibrium situations. Here, through re-analysis of Ag atom magnetic trap loss, a general method for creating, in equilibrium, a host of vdW molecules in the very low temperature (and high cooling capacity) conditions of dilution refrigerator cooled...

Sat, January 1, 2011

Strongly Interacting Isotopic Bose-Fermi Mixture Immersed in a Fermi Sea

Fri, January 1, 2010

Rare-earth Atom Collisional Anisotropy

Fri, January 1, 2010

Thermometry and Refrigeration in a Two-Component Mott Insulator of Ultracold Atoms

In this work [1], we describe and analyze theoretically the two techniques of spin-gradient thermometry and spin gradient demagnetization cooling developed earlier by our group [2, 3].

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