Researchers
have revealed a way to get around Heisenberg's Uncertainty Principle, one of
the fundamental discoveries of 20th century physics. To accomplish this they
entangled two small – but nevertheless macroscopic – vibrating drums, a extraordinary
advance in itself.
The
uncertainty principle shows that it is impossible to know the position and
momentum of an object exactly at the same time. The inaccuracy in the
measurement of each, multiplied together, must be greater than half the Planck
constant. Calculating one will always create an uncertainty that produces disturbance
about the other by a phenomenon known as quantum backaction. While this makes
for plenty of jokes about car trips or billiard balls, on a human scale this influence
is insignificant. Instead, when considering objects of very small mass, principally
subatomic particles, it places major limitations on our ability to know the
world.
However,
Dr Mika Sillanpää of Aalto University, Finland has revealed the principle can
be evaded when two objects are linked to each other by the process known as
quantum entanglement. Sillanpää and colleagues generated tiny aluminum
drumheads and used microwaves to make them vibrate out of phase billions of
times a second.
Though not
naturally connected, the drumheads are entangled so that changes to one has an effect
on the other. "One of the drums reacts to all the forces of the other drum
in the opposing way, kind of with a negative mass", Sillanpää said in a
statement.
Entangling
these two is an important achievement in itself. Actually, the similar edition
of Science that carries Sillanpää's paper has a statement from a team led by Dr
Shlomi Kotler of the University of Colorado that accomplished something very
similar.
Both teams
used drumheads that are small – 10 µm, or a fifth of the width of a human hair,
but still big enough to see without a microscope. Quantum entanglement has been
revealed for decades with objects the size of a few atoms or smaller, but has
proven challenging to scale up. Statements of quantum entanglement at a
macroscopic scale have been made before, but these have relied on implications
that have left room for doubt. Kotler in precise has been able to measure the
entanglement more directly, generating greater assurance in the results.
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