From The Nobel Prize 2022
Edited by - Amal Udawatta
Alain Aspect, John
Clauser and Anton Zeilinger have each conducted groundbreaking experiments
using entangled quantum states, where two particles behave like a single unit
even when they are separated. Their results have cleared the way for new
technology based upon quantum information.
The ineffable effects
of quantum mechanics are starting to find applications. There is now a large
field of research that includes quantum computers, quantum networks and secure
quantum encrypted communication.
One key factor in this
development is how quantum mechanics allows two or more particles to exist in
what is called an entangled state. What happens to one of the particles in an
entangled pair determines what happens to the other particle, even if they are
far apart.
For a long time, the
question was whether the correlation was because the particles in an entangled
pair contained hidden variables, instructions that tell them which result they
should give in an experiment. In the 1960s, John Stewart Bell developed the
mathematical inequality that is named after him. This states that if there are
hidden variables, the correlation between the results of a large number of
measurements will never exceed a certain value. However, quantum mechanics
predicts that a certain type of experiment will violate Bell’s inequality, thus
resulting in a stronger correlation than would otherwise be possible.
John Clauser developed
John Bell’s ideas, leading to a practical experiment. When he took the
measurements, they supported quantum mechanics by clearly violating a Bell
inequality. This means that quantum mechanics cannot be replaced by a theory
that uses hidden variables.
Some loopholes
remained after John Clauser’s experiment. Alain Aspect developed the setup,
using it in a way that closed an important loophole. He was able to switch the
measurement settings after an entangled pair had left its source, so the
setting that existed when they were emitted could not affect the result.
Using refined tools
and long series of experiments, Anton Zeilinger started to use entangled
quantum states. Among other things, his research group has demonstrated a phenomenon
called quantum teleportation, which makes it possible to move a quantum state
from one particle to one at a distance.
“It has become
increasingly clear that a new kind of quantum technology is emerging. We can
see that the laureates’ work with entangled states is of great importance, even
beyond the fundamental questions about the interpretation of quantum
mechanics,” says Anders Irbäck, Chair of the Nobel Committee for Physics.
Learn more
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