[EAS] Light in a Bottle

pjk pjk at design.eng.yale.edu
Sat Dec 13 14:32:45 EST 2003

Subject:   Light in a Bottle

Two versions of announcements about another remarkable
accomplishment in "quantum engineering." 
Long ago, as a child, I recall reading a tale involving the bottling
of sunlight. Was it one of the tales of Baron Munchhausen (published
originally in a 1786 book by Rudolf Raspe, though probably best
known because of Terry Gilliam's 1989 film)? Perhaps one of my
readers recalls. 
In any case, we are getting close to doing it.  --PJK

(from NewsScan Daily, 11 December 2003)

Physicists at Harvard University say they have managed to bring
light to a  complete standstill for a fraction of a second before
sending it on its  way. The research builds on work published in
2001 that described "storing"  light pulses briefly when individual
particles of light, or photons, were  taken up by atoms in a gas.
The new work actually stops the light pulse for  a few hundredths of
a second, says Harvard physicist Mikhail D. Lukin: "We  have
succeeded in holding a light pulse still without taking all the
energy  away from it." The research could allow scientists to use
light particles  for storing and processing data, and for highly
secure communications  transmissions. (AP/Edmonton News 11 Dec 2003)

The American Institute of Physics Bulletin of Physics News
Number 665 December 10, 2003   by Phillip F. Schewe, Ben Stein, and
James Riordon

pulse of light has been stopped without losing its optical energy. A
few years ago, two different Harvard groups succeeded in slowing and
then storing a pulse of light in atomic vapor.  In that work the
propagation of light pulses was halted by vesting the properties of
incoming photons into the spin orientations of the atoms in the
vapor.  Thus light pulses had been stopped by ceasing to exist in
the form of electromagnetic energy while ceding all of its signal
qualities to the atomic vapor.   Later they could be reconstituted
into propagating light beams
<http://www.aip.org/enews/physnews/2001/split/521-1.html>.  Now, a
new experiment, also conducted at Harvard, brings light to a halt
but leaves the pulse intact as an optical entity.  Mikhail Lukin and
his colleagues begin as before by converting the incoming light
pulse into a corresponding ensemble of spins in a vapor.  But then
something else is added: a pair of  counter-propagating laser beams
ease the pulse back into existence.  But the control beams also
serve to herd  the atoms in just such a way as to cause them to act
like a stack of mirrors.  In this hall of atomic mirrors, the
original pulse still exists as  electromagnetic radiation, but it
cannot move---it persists within a fixed stationary envelope.  Thus
the light pulse containing optical photons is literally frozen in
space. It can be held and  released into motion again on command.
The present experimental work follows a theoretical proposal
published  last year in Physical Review Letters (89, 143602, 2003).
Researchers believe that the new phenomenon that they demonstrated
may be used to controllably localize, shape  and guide stationary
photonic pulses in three spatial dimensions. This can create ideal
conditions for different light beams to interact or "talk" to each
other since localized light electromagnetic energy can be held in
one place for a relatively long time.  Such techniques may enable
nonlinear interactions between  faint laser pulses that could be
useful for processing light signals.  For example, this process
might serve in optical computing, where calculations are carried out
not with electrons but with photons. Another ambitious goal would be
 to perform logic operations between individual photons in future
quantum computers.  But the researchers say that much further work
is still needed to determine if the present work can aid of any of
these applications. For now, its just another step toward ultimate
control of light. (Bajcsy, Zibrov, and Lukin, Nature, 11 December

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