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Physicists find chance, even if slim, that the muon detections indicate the existence of some new,
muons bemusing long-lived elementary particle and perhaps a previously unknown force. Such
Puzzling results may signify a finding could revolutionize the under-
mystery particle or new force standing of the universe, says Mark Kruse
of Duke University in Durham, N.C.
By Ron Cowen
Physicists are puzzling over a bunch of
measly muons. In experiments at the
Fermi National Accelerator Laboratory
in Batavia, Ill., researchers have detected
too many muons where there should be
Muons are heavy cousins of electrons.
Most physicists believe a mundane explanation exists for the muons’ aberrant
location in this experiment. But there’s a
Fermilab’s CDF experiment observed an
unexpected abundance of muons.
Only two-thirds of the many collaborators on the experiment, including Kruse,
consented to have their names listed on
the paper announcing the muon puzzle,
posted online October 29 ( arxiv.org/
abs/0810.5357). Many believe the puzzle will be solved with ordinary physics,
perhaps some overlooked property of the
Kruse thinks this will likely be the
case, but nonetheless he and colleagues
speculate on novel elementary particles
that might be required if the muon riddle
endures ( arxiv.org/abs/0810.5730). And
a physicist not affiliated with the experiment, Matt Strassler of Rutgers University’s campus in Piscataway, N.J., contributes
his own musings in a November 10 online
posting ( arxiv.org/abs/0811.1560).
A way to crack quantum encryption
Time-travel technique could break supposedly secure codes
By Rachel Ehrenberg
Quantum physics offers James Bond
and his ilk much more than a bit of solace — it permits quantum encryption, a
completely spyproof way to send coded
information. Any bad guy eavesdropping
on Bond’s messages to M could always
But now physicists suggest that quantum codes may be breakable using a trick
that even Bond hasn’t mastered — time
travel. By exploiting hidden paths to the
past — routes that are predicted by some
of Einstein’s equations — a nemesis could
eavesdrop on a quantum-coded message
without alerting the senders.
Time travel, possibly through a wormhole, appears to make it possible to distinguish quantum information that usually
can’t be distinguished. That ability would
disrupt the absolute security of quantum encryption, physicist Todd Brun of
the University of Southern California in
Los Angeles and colleagues report online
November 7 ( arxiv.org/abs/0811.1209).
“I believe it is a sound result that quantum cryptography would not work in this
world,” comments Charles Bennett, who
with Gilles Brassard developed the first
quantum encryption protocol in 1984.
“You might say it is a weakness of quantum cryptography —but if there were
wormholes, people could go back in time
and do worse feats of mischief than reading secret messages,” says Bennett.
Encryption relies on both sender and
recipient having a secret shared key to
create or decipher the coded message. As
long as both parties are the only ones with
the key to the code, “secret” messages can
be sent in plain sight, yet remain secret.
Traditional codes for sending messages
between distant communicators are vulnerable because an eavesdropper might
intercept the key. But in the quantum
world, a key can be transmitted securely
because quantum information is changed
when looked at, alerting sender and recipient when an eavesdropper is afoot.
For quantum eavesdroppers, “the only
way not to be detected is to acquire no
information because measurements disturb the state,” Brun says.
Detection of quantum-code eavesdropping is possible because a quantum particle
(say a photon) can exist in a fuzzy mixture
of states. Measuring the particle converts
it to a particular “preferred state.” Imagine
a bird in flight. In the quantum world, the
flying bird may be anything from a pelican to a chickadee. But once it is caught,
it becomes one bird — which kind depends
on the net used to catch it.
Say Alice sends Bob a chickadee that
Eve intercepts. If Eve uses a big net, she
won’t catch a chickadee, but a pelican. As
Eve sends intercepted birds to Bob, eventually he and Alice will realize that Bob
is getting big birds that should be small.
The new paper shows how Eve could
send Alice’s bird through a spacetime
wormhole (technically, a “closed timelike curve”) that allows time travel. Eve’s
bird could interact with its earlier self at
the wormhole’s other end and become a
distinguishable bird that fits the code.
This scenario can’t be ruled out, says
Bennett, of IBM’s Watson Research Center
in Yorktown Heights, N. Y. The existence of
wormholes “is not totally impossible, but
it is pretty damn unlikely,” he says.