---------- Forwarded message ---------- Date: Tue, 20 Feb 2007 14:17:20 -0500 From: [EMAIL PROTECTED] To: [EMAIL PROTECTED] Subject: Physics News Update 812 PHYSICS NEWS UPDATE The American Institute of Physics Bulletin of Physics News Number 812 February 20, 2007 by Phillip F. Schewe, Ben Stein, and Davide Castelvecchi www.aip.org/pnu SLOWED LIGHT HANDED OFF. Several years ago, physicists gained the ability to slow a beam of light in a gas of atoms; by manipulating the atoms? spins the energy of and information contained in the light could be transferred to the atoms in a coherent way (http://www.aip.org/pnu/2001/split/521-1.html). By turning on additional laser beams, the original light signal, which we can think of as having been idling or temporarily stored in the atom cloud, could be reconstituted and sent on its way. Now, one of the first researchers to do this, Lene Hau of Harvard, has added an extra layer to this story. She and her colleagues, halting and storing a light signal in a gas of cold atoms-in this case a Bose-Einstein condensate (BEC) of sodium atoms-then transfer the signal, now in the form of a coherent pulse of atom waves rather than light waves, into a second BEC of sodium atoms some 160 microns away, from which, finally, the signal is revived as a conventional light pulse. This feat, the sharing around of quantum information in light-form and in not just one but two atom-forms, offers great encouragement to those who hope to develop quantum computers. (Ginsberg et al., Nature, 8 February 2007.) ULYSSES IN THE UNDERWORLD. Getting a spacecraft much out of the plane of the ecliptic, where all the planets reside, is hard to do with rocket power alone. However, by using the gravitational pull of Jupiter as a sling, the Ulysses craft, launched in 1990, leveraged itself into a nearly circumpolar orbit over and under the sun. As of now Ulysses finds itself beneath the sun?s southern pole for the third time, and will continue to make a variety of radiation and particle measurements (http://ulysses.jpl.nasa.gov/). RADIUM ATOMS TRAPPED. Physicists at Argonne National Lab have laser-cooled and trapped radium atoms for the first time. Surprisingly, room temperature blackbody photons- thermal radiation over a wide spectrum emitted by the apparatus itself-- were found to play a critical role in the laser-trapping of this rare and unstable element. This represents the heaviest atom ever trapped by laser light. Using only 20 nanograms of Ra-225 (halflife of 15 days) and one microgram of Ra-226 (halflife of 1600 years), the Argonne scientists held tens of Ra-225 and hundreds of Ra-226 atoms in the laser trap. It was particularly challenging to trap radium because quantities are scarce and the atomic structure is not well studied and understood. Why go through the trouble of trapping radium atoms? Because it might provide a chance to detect a violation of time-reversal symmetry (abbreviated with the letter T), which would manifest itself as an electric dipole moment (EDM); that is, even though the atom as a whole is charge neutral, there might exist a slight offset between the negative and positive charge within the atom along its spin axis. EDM searches have been ongoing for over 50 years and continue to yield smaller and smaller limits on the size of these T-violating interactions. These limits place constraints on theories beyond the Standard Model of particle physics and explanations for the matter- antimatter asymmetry in the universe. Next generation EDM searches may take advantage of rare isotopes such as Ra-225, which are expected to be extremely sensitive to T-violation owing to their non-spherical 'egg'-shaped nucleus. For the rare and unstable radium atoms, a laser trap offers a promising path to such a measurement. (Guest et al., Physical Review Letters, upcoming article; lab website, http://www-mep.phy.anl.gov/atta/research/radiumedm.html) *********** PHYSICS NEWS UPDATE is a digest of physics news items arising from physics meetings, physics journals, newspapers and magazines, and other news sources. It is provided free of charge as a way of broadly disseminating information about physics and physicists. For that reason, you are free to post it, if you like, where others can read it, providing only that you credit AIP. Physics News Update appears approximately once a week. AUTO-SUBSCRIPTION OR DELETION: By using the expression "subscribe physnews" in your e-mail message, you will have automatically added the address from which your message was sent to the distribution list for Physics News Update. If you use the "signoff physnews" expression in your e-mail message, the address in your message header will be deleted from the distribution list. Please send your message to: [EMAIL PROTECTED] (Leave the "Subject:" line blank.)
