IN an echo of Star Trek, scientists have succeeded in making a
鈥渢ransporter鈥�. The system may be far from the sci-fi visions of
teleportation鈥攊t can only 鈥渂eam鈥� a photon of light across a desk. But the
team says the technique is an important victory for quantum mechanics.
One of the main obstacles to teleportation鈥攅ven of tiny
particles鈥攊s the Heisenberg uncertainty principle. According to this
principle, it is impossible to measure accurately all the properties of any
object, such as an atom. This makes it impossible to replicate that atom
elsewhere.
快猫短视频s have hoped to get round this by using 鈥渆ntangled鈥� photons: measure
the properties of one and you can work out those of the other. A sender (Alice)
and a receiver (Bob) could each be given one of a pair of entangled photons.
Alice could merge hers with a particle in an unknown quantum state and measure
their combined properties. If Alice told Bob the results, he could reconstruct a
particle that was identical to Alice鈥檚 using his own entangled photon
(This Week, 26 July, p 6).
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Unfortunately, scientists have met huge technical hurdles trying to get
particles to interact with entangled photons in this way. But in an upcoming
issue of Physical Review Letters, physicists from the University of
Cambridge and the University of Rome claim that they have at least demonstrated
the principle of the technique鈥攂y 鈥渢eleporting鈥� one of the entangled
photons themselves.
By shooting photons through calcite crystals, the team split them into two
entangled photons, 1 and 2. 鈥淎lice鈥� equipment at one end of a table measured the
polarisation of photon 1, and transmitted the information to a 鈥淏ob鈥� detector at
the other end of the table. The researchers could then use this information to
create an identical copy of photon 1 at Bob鈥檚 end.
鈥淚t鈥檚 very important,鈥� says Francisco De Martini, one of the researchers.
鈥淥ur technique is very nice. There鈥檚 no need for a third particle.鈥�
William Wooters, a physicist at Williams College in Williamstown,
Massachusetts, agrees. 鈥淲hat鈥檚 most exciting for me is that it illustrates a
wonderfully mysterious property of nature,鈥� he says. He adds that if
teleportation schemes can be perfected, they could one day be put to use in
quantum computers.