of T physicists have developed a way to entangle photons
which could ultimately lead to an extremely precise
new measurement system.
study appears in the May 13 issue of the journal Nature.
The findings could ultimately prove useful in developing
ways to measure gravitational waves or the energy
structure of atoms, and could also help in the development
of "quantum computers." (Quantum computers
work according to the principles of quantum mechanics,
which describes atoms, photons, and other microscopic
studies have theorized that quantum computers using
entangled photons could perform calculations far more
quickly than current computers. "We know that
today's computers are approaching limits of size and
speed," says lead author and post-doctoral fellow
Morgan Mitchell. "Quantum computing offers a
possible way to move beyond that. Our research borrows
some tricks from quantum computing and applies them
to precision measurement."
working with Professor Aephraim Steinberg and graduate
student Jeff Lundeen, first prepared three photons
each with a different state of polarization. The researchers
directed one photon along a main pathway or "beam,"
then added a second photon. If researchers determined
that both photons continued down the main beam, they
concluded the two had become entangled. A third photon,
with yet another polarization, was then added.
The team was able to create a three-photon state in
58 per cent of their attempts. "Nobody has taken
three distinct photons and made a three-photon entangled
state before," he says. The entire process occurred
within nanoseconds over a physical span of less than
researchers then demonstrated the use of the three-photon
entangled state to make extremely precise measurements.
To do so, they used an experiment based on a paradox
associated with quantum mechanics, which suggests
that a particle can be in two places at once.
observing the movement of the photons past a series
of mirrors and filters, the team was able to determine
how far the photons had traveled.
the team used photons in a three-photon state, the
system could provide measurements that were three
times as precise as those made by a single photon.
Since the new system, in theory, could incorporate
an even larger number of photons, it could someday
lead to a measurement system with significantly greater
accuracy than anything that currently exists. The
next step could be a practical test involving a measurement,
study was funded by the Natural Sciences and Engineering
Research Council of Canada, Photonics Research Ontario,
the Canadian Institute for Photonic Innovations and
the DARPA-QuIST program.