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Date: Wed, 21 Nov 2001 14:10:33 -0500 (EST)
From: AIP listserver
To: physnews-mailing@aip.org
Subject: update.566
PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 566 November 21, 2001 by Phillip F. Schewe, Ben
Stein, and James Riordon
HIDDEN OBJECTS REVEALED WITH QUANTUM
HOLOGRAPHY. Second sight and remote viewing are terms used
to explain charlatans' supposed psychic ability to see hidden
objects in terms of pseudoscientific gibberish. Quantum
holography, on the other hand, is a method firmly grounded in
modern physics that permits the imaging of hidden objects with
entangled photons. Of the quantum entanglement phenomena that
Einstein described as "spooky action at a distance," quantum
holography may be the spookiest to date. Researchers at Boston
University's Quantum Imaging Laboratory (Bahaa Saleh,
617-353-7176, besaleh@bu.edu) propose to create holographic
images of objects concealed in a spherical chamber. Ideally, a
small opening in the chamber wall permits light to enter, but lets
no light out. The photons in a beam of light directed through the
hole scatter from the enclosed object, and ultimately strike the
inner wall of the chamber (see figure at
http://www.aip.org/mgr/png). According to the scheme, the inside
of chamber would be designed to detect the time when a photon
hits the wall but not where it hits. Classically, there is no way to
generate an image of an object with this sort of configuration.
Quantum mechanically, however, it's possible to build a hologram
of the hidden object provided that the photons in the illuminating
beam are entangled with photons in another beam. Each photon in
an entangled pair has properties (such as momentum or
polarization) that are unknown until a measurement is performed
on one photon or the other. When a property of one of the photons
is measured, corresponding information about its entangled mate is
instantly determined. That may seem spooky enough, but in
quantum holography, things get spookier still. Holograms are
typically constructed with interfering beams of light, which
provides more information about a subject than simple
illumination can. The additional information helps build a three
dimensional image of a three dimensional object. In quantum
holography, the researchers measure the simultaneous arrivals of
an illuminating photon that is sent into the chamber and a
companion photon in the other entangled beam. This measurement
tells the researchers about the interference of various possible
paths that the single photon inside the chamber could travel. And
it's the interference of the possible paths that encodes the
holographic image of the hidden object. Very spooky indeed. For
the moment, quantum holography exists only on paper. But the
researchers assert that there are no technological obstacles to the
proposal, and they hope to begin building an experimental system
soon. (Ayman F. Abouraddy, Bahaa E. A. Saleh, Alexander V.
Sergienko, and Malvin C. Teich, Optics Express, 5 November
2001.)
PUZZLING NEUTRINO RESULTS AT FERMILAB. Particle
[SSZ: Text deleted]
