---------- Forwarded message ---------- Date: Wed, 16 Nov 2005 13:55:09 -0500 From: [EMAIL PROTECTED] To: [EMAIL PROTECTED] Subject: Physics News Update 754
PHYSICS NEWS UPDATE The American Institute of Physics Bulletin of Physics News Number 754 November 16, 2005 by Phillip F. Schewe, Ben Stein HYPER-ENTANGLED PHOTON PAIRS. Physicists at the University of Illinois have demonstrated for the first time the entanglement of two objects not merely in one aspect of their quantum natures, such as spin, but in a multitude of ways. Entanglement is the quantum affinity between or among particles (such as atoms or photons) in which the measurement of some property for one particle automatically and instantaneously determines the corresponding property of the other particle. Take the case of two photons entangled with respect to polarization, the orientation of the electric field associated with the photon. The photons, until detected, have no spin orientation; this is the principle of quantum indeterminacy. Indeed, both photons are said to be in a superposition of arbitrary -- but parallel -- polarization states. Consequently, each photon has a 50% likelihood of being measured to have any polarization state---e.g., +45 or -45 degrees. If now one photon's polarization is measured to be +45, then its entangled twin will surely also be polarized along +45 owing to the way the photons are made in this setup. One of the chief hopes of entanglement research is to exploit the superposition idea and the entanglement idea for performing unusually fast quantum computation. In the Illinois experiment, two photons, produced in a "down-conversion" process whereby one photon enters an optical crystal and sunders into two lesser-energy correlated daughter photons, are entangled not just in terms of polarization, but also in a number of other ways: energy, momentum, and orbital angular momentum (see http://www.aip.org/pnu/2005/split/721-3.html). Actually, the photon pair can be produced in either of two crystals, and the uncertainty in the production details of the individual photons is what provides the ability to attain entanglement in all degrees of freedom. Is it better to entangle two particles in ten ways or ten particles in two ways? They're probably equivalent, says, Paul Kwiat, leader of the Illinois group, but for the purpose of quantum computing or communication it might be of some advantage if multiple quantum bits (or qubits) of information can be encoded in a single pair of entangled particles. Kwiat (217-333-9116, [EMAIL PROTECTED]) says that his lab detects a record two million entangled photon pairs per second with ample determination of numerous properties, allowing a complete characterization of the entanglement produced. (Barreiro et al., Physical Review Letters, upcoming article) NORTH PACIFIC "BOING" ATTRIBUTED TO MINKE WHALES. Human singers send their voice into the supporting medium of air. Whales send their songs into ocean water. One particular song, a sort of fluttering echo, or"boing," sound first heard by human listeners in the North Pacific Ocean in the 1950s (and recorded by US Navy submarines) baffled scientists. Where was it coming from? Only now have the sounds been identified as coming from minke whales. Shannon Rankin and Jay Barlow, scientists at the National Marine Fisheries Service in La Jolla, California, have gathered hydrophone data in the body of ocean between Mexico and Hawaii and combined this with visual sightings of the marine mammals. Not only has the source been traced to minke whales, but the songs seem to be somewhat different on either side of a certain longitude. To the east, the boing sound is issued at a frequency of about 92 Hz and an average duration of 3.6 seconds. The west boing, by contrast, consists of a 135-Hz vocalization with a duration of about 2.6 seconds. The acoustic trace is both frequency modulated (FM) and amplitude modulated (AM). (Journal of the Acoustical Society, November 2005; numerous whale sounds, including the boing, can be accessed at http://swfsc.nmfs.noaa.gov/PRD/PROGRAMS/CMMP/accsurv.html) QUANTUM SOLVENT. Scientists at the Ruhr-Universitat Bochum in Germany have performed high-precision, ultracold chemical studies of nitrogen oxide (NO) molecules by inserting them into droplets of liquid helium (see figure at http://aip.org/png/2005/240.htm). NO, Science magazine's "molecule of the year"for 1992, is important because of its role in atmospheric chemistry and in signal transduction in biology. A radical is a molecular entity (sometimes charged and sometimes neutral) which enters into chemical reactions as a unit. To sharpen our understanding of this important molecule and its reactions, it would be desirable to cool it down, the better to observe its complex spectra of quantum levels corresponding to various vibrational and rotational states. In the new experiment, liquid helium is shot from a cold nozzle into vacuum. The resultant balls, each containing about 3000 atoms, are allowed to fall into a pipe where NO molecules are lurking. The NO is totally enveloped and, within its superfluid-helium cocoon at a temperature of about 0.4 K, it spins freely. The helium acts provides a cold environment but does not interact chemically with the NO molecules. Because of this a high-resolution infrared spectrum of NO in fluids could be recorded for the first time. NO has been observed before in the gas phase, but never before has such a high resolution spectrum be seen in the helium environment. (Haeften et al., Physical Review Letters, 18 November 2005; contact Martina Havenith, [EMAIL PROTECTED]; lab website at http://www.ruhr-uni-bochum.de/pc2/helium_short_en.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. 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