EXTREME
MAKEOVER
the quantum mechanics edition
By Garth Boucher
he “Age of Information” is
about to get an extreme makeover.
The makeover is coming at the hands of physicists, mathematicians and
computer scientists who, for the first time, are successfully
harnessing the mind bending principles of quantum mechanics to encode
and process information.
Currently,
we encode our information classically — that is, using
physical systems subject to Sir Isaac Newton’s timehonoured laws
of physics where particles collide in predictable, calculable ways. The
basic unit of information currency in this realm is the bit which represents
one of two states – on or off, 1 or 0. The bit is physically
realized in a variety of ways, including magnetic regions on disks,
voltages
in circuitry, pits on compact disks or even pencil marks
on paper.
The challenge
is to bridge the gaping chasm that separates Newton’s
classical physics and the world of quantum mechanics where
particles can be in two places at the same time.
Enter U of
C physics professor Alexander Lvovsky.
Lvovsky leads the Quantum Information Technologies group (QIT), which
is part of U of C’s recently launched Institute for Quantum Information
Science.
His team
is investigating the possibility of using single portions or “quanta” of light — photons — as a means of
carrying information. The first hurdle in this process is immediate.
“
It’s not easy to generate just one photon” says Lvovsky. “It’s
only recently that we’ve learned how to do this in a controlled
manner.”
The photons
are created with distinct polarizations — “vertical” and “horizontal,” corresponding
with the two states of a classical bit — 1 and 0.
But it is
here that the counterintuitive quantum world imposes its bewildering
and bizarre will. Photons
can
in fact be
in two different states at the same time, effectively
attaining a superposition
of the “1
or 0” state. It is something we have no analogy
for in our macroscopic world of everyday experience.
Understanding
and manipulating quantum superpositions is one of the keys in making
the transition from
classical to quantum information technology.
Initially considered
a confusing impediment,
quantum
phenomena is something researchers like Lvovsky
are steadily coming to
terms with
in a practical sense. They now realize that this
unique quantum
capability has the potential to significantly
increase the amount of information
that can be carried. The quantum bits of information
have naturally been dubbed “qubits”.
Qubits are
of little practical interest however, unless they can be reliably stored
and retrieved.
This problem
forms the second axis
of research pursued by Lvovsky and his team. “
All computers, quantum or classical, require memory” explains Lvovsky. “But
this is problematic for photons — they are so tiny and so fast
that there aren’t many materials that they will interact with.”
One possibility
the QIT team is investigating is the use of elemental rubidium vapor
as a kind of
receptacle into which an injected
photon might transfer or “store” its quantum state. This is proving
to be an extremely delicate and technically demanding process as the
photons generated need to have precisely the right properties or they
will effectively “miss” the rubidium atoms.
If the details
of Lvovsky’s research seem abstract and difficult
to grasp, his vision of the importance of his team’s research is
at once exciting and sobering.
“
The impact of quantum information technology ranges from revolutionizing
drug research to making the cryptographic codes used to protect today’s
most sensitive information obsolete and easy to crack.” Lvovsky cites
credit card purchases over the Internet as an example of a type of
transaction for which
security could no longer
be
guaranteed with the availability of quantum computers.
“
An individual with such technology could totally disrupt the world’s
banking and other security systems. For this reason, governments
are in a hurry to fund this research.”
