[THS] Forget Schrodingers Cat. Could We Make Schrodingers Virus?
vignes at wanadoo.fr
Sun Sep 20 19:38:03 CEST 2009
Forget Schrodingers Cat. Could We Make Schrodingers Virus?
Schrodingers catSchrödingers Cat may be the most famous thought experiment of
all time, but due to its quantum trickiness it must remain in the realm of the
hypothetical for the time being. However, researchers suggest they might just be
able to pull off a similar, smaller-scale experiment they call Schrödingers virus.
The physicist Erwin Schrödinger came up the the feline thought experiment in the
1930s, presenting it as a caution against applying quantum rules to the real,
. At its most fundamental level, quantum mechanics says that
particles can only exist in discrete states. For example, researchers can measure the
direction a particle spins as either up or down, but nothing in between. Yet, as long
as no one is looking, the particle exists in a combination of both states
simultaneously, a strange blend known as a superposition [Nature News].
Schrödinger proposed an experiment where a cat would be put in box containing a
vial of poison gas. A hammer would be suspended ready to smash down on the vial if
triggered by the decay of a single atom of radioactive material. If no one looked
inside the box, Schrödinger said, the radioactive atom would be in a
superpositionboth intact and decayedand therefore the cat would exist in two
states as well, being simultaneously alive and dead.
To take a step towards this logical impossibility, researchers propose in a paper
posted on the arXiv pre-print server that they start with a much smaller living
organism, a virusalthough other researchers point out that there is still debate over
whether viruses are truly alive. Still, the researchers say that since they think theyve
figured out a way to conduct an experiment putting a single virus in a superposition,
it may as well be tried.
The proposed experiment would involve trapping a single virus in a vacuum
chamber, and then gradually cooling it and slowing it down until it rests, motionless,
in its lowest possible energy state. Finally a single photon, a light particle, would be
beamed into the chamber, and as long as nobody peeked inside the chamber the
virus would be placed in a superposition of two states: both moving and not.
Researcher Oriol Romero-Isart, one of papers coauthors, say the experiment would
only work if the virus has certain properties: if its dielectric (meaning it doesnt
conduct electricity), can survive the vacuum and appears transparent to laser light,
which would otherwise rip it apart. As luck would have it, Romero-Isart and co say
that several viruses fit the bill. The common flu virus is known to be able to survive in
a vacuum, seems to have the required dielectric properties and may well be
transparent to a careful choice of laser light. The tobacco mosaic virus, to all intents
and purposes a dielectric rod, looks like another good candidate [Technology
Some experts say the experiment may have limited use. Physicist Martin Plenio (whos
not involved in the proposed research) says theres no reason to think that a virus will
behave differently than an inorganic molecule, but he still thinks that testing relatively
large objects, whether viruses or molecules, could prove interesting. According to
quantum mechanics, it should be possible for macroscopic objects like cars and
people to enter superpositions, but that never appears to happen. Studying relatively
large objects, says Plenio, may help physicists learn where the quantum world ends
and the our macroscopic world begins [Nature News].
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