Alain Aspect
2012 Albert Einstein Medal Recipient
Institut d'Optique
Since the early days of quantum mechanics, the interferences that are apparent
between spatially separated trajectories of quantum particles has not ceased to
fascinate both professional physicists and the broader public. In this lecture,
Prof. Aspect will present results from a series of experiments - each of which
has been realized with a single photon (i.e. a single quantum of light) - that
serve to emphasize the weirdness of the concept of ‘wave particle
duality’, an idea that is at the root of the quantum revolution
of the 20th century. The single photon sources used in these experiments
have recently left the laboratory, and are now an important resource in the
technological domains of quantum information and quantum cryptography.
Prof. Aspect is a giant in the area of experimental tests of fundamental
concepts in quantum mechanics using optics. In the early 1980's he performed
the elusive ‘Bell test experiments’ that showed Albert
Einstein, Boris Podolsky and Nathan Rosen's reductio ad absurdum of quantum
mechanics, namely that quantum mechanics implied a ‘ghostly action
at a distance’ (the EPR paradox), was neither absurd nor ghostly!
That is, the ‘ghostly action at a distance’ that so
bothered Einstein appears to be an essential and unavoidable fact of nature that
we simply must reconcile ourselves to. These and other experiments performed
by Prof. Aspect have contributed enormously to our understanding regarding
the true nature of the quantum world, including core ideas and concepts
like ‘wave-particle duality’ and ‘quantum
entanglement’ that are hot subjects in everything from books
popularizing physics to the Big Bang Theory.
Thursday, November 19th 2015, 19:00
Frank Dawson Adams Building, Adams Auditorium
From Einstein to Wheeler:
Wave Particle Duality for a Single Photon
Since the early days of quantum mechanics, the interferences that are apparent
between spatially separated trajectories of a single particle has not ceased
to fascinate both professional physicists and the broader public. In this
lecture I will present results from a series of experiments - each of which
has been realized with a single photon (i.e. a single quantum of light) - that
serve to emphasize the weirdness of the concept of “wave particle
duality”, an idea that is at the root of the quantum revolution
of the 20th century. The single photon sources used in these experiments
have recently left the laboratory, and are now an important resource in the
technological domains of quantum information and quantum cryptography.
Friday, November 20th 2015, 15:30
Ernest Rutherford Physics Building, Keys Auditorium (room 112)
Anderson localization of ultra-cold atoms:
a quantum simulator
In the early 1980's, Feynman realized that many-body entangled systems pose
an insurmountable challenge to classical computers, and suggested that a
promising way to attack the problem is to simulate the situation with an
equivalent quantum system (R. P. Feynman,
“Simulating physics with computers”, International Journal of
Theoretical Physics 21, 467-488 [1982]).
Since the early 2000's, ultra-cold atoms have been found an excellent system
to realize Feynman's program, and realize quantum simulators of difficult
condensed matter problems, where many electrons are entangled. One can
cite the Mott insulator to superconductor transition in a lattice, or the
BEC-BCS transition, to name only a few. In our group, we study the problem of
quantum particles in a disordered potential, and in particular the celebrated
Anderson localization phenomenon, i.e. the total suppression of conductivity
beyond a certain level of disorder, a phenomenon impossible to understand in
a classical framework. Our experiments use atomic Bose-Einstein Condensates
in optical disordered potentials based on laser speckle.
I will describe the Anderson localization phenomenon, present some experimental
results that shed a new light on strong and weak localization, and evoke the
open problems.
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