Cavity quantum electrodynamics
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Cavity quantum electrodynamics ( cavity QED ) is the study of the interaction between light confined in a reflective cavity and atoms or other particles, under conditions where the quantum nature of photons is significant. It could in principle be used to construct a quantum computer .
The case of a single 2-level atom in the cavity is mathematically described by the
Jaynes–Cummings model
, and undergoes
vacuum Rabi oscillations
, that is between an excited atom and
photons, and a ground state atom and
photons.
If the cavity is in resonance with the atomic transition, a half-cycle of oscillation starting with no photons coherently swaps the atom qubit's state onto the cavity field's,
, and can be repeated to swap it back again; this could be used as a single photon source (starting with an excited atom), or as an interface between an atom or
trapped ion quantum computer
and optical
quantum communication
.
Other interaction durations create
entanglement
between the atom and cavity field; for example, a quarter-cycle on resonance starting from
gives the
maximally entangled state
(a
Bell state
)
. This can in principle be used as a
quantum computer
, mathematically equivalent to a
trapped ion quantum computer
with cavity photons replacing phonons.
Nobel Prize in Physics
The 2012 Nobel Prize for Physics was awarded to Serge Haroche and David Wineland for their work on controlling quantum systems. [1]
Haroche was born 1944 in Casablanca, Morocco, and in 1971 gained a PhD from Université Pierre et Marie Curie in Paris. He shares half of the prize for developing a new field called cavity quantum electrodynamics (CQED) – whereby the properties of an atom are controlled by placing it in an optical or microwave cavity. Haroche focused on microwave experiments and turned the technique on its head – using CQED to control the properties of individual photons. [1]
In a series of ground-breaking experiments, Haroche used CQED to realize Schrödinger's famous cat experiment in which a system is in a superposition of two very different quantum states until a measurement is made on the system. Such states are extremely fragile, and the techniques developed to create and measure CQED states are now being applied to the development of quantum computers.
See also
References
- Herbert Walther; Benjamin T H Varcoe; Berthold-Georg Englert; Thomas Becker (2006). "Cavity quantum electrodynamics" . Rep. Prog. Phys . 69 (5): 1325–1382. Bibcode : 2006RPPh...69.1325W . doi : 10.1088/0034-4885/69/5/R02 . S2CID 122420445 . Microwave wavelengths, atoms passing through cavity
- R Miller; T E Northup; K M Birnbaum; A Boca; A D Boozer; H J Kimble (2005). "Trapped atoms in cavity QED: coupling quantized light and matter" . J. Phys. B: At. Mol. Opt. Phys . 38 (9): S551–S565. Bibcode : 2005JPhB...38S.551M . doi : 10.1088/0953-4075/38/9/007 . S2CID 1114899 . Optical wavelengths, atoms trapped
- 1 2 Johnston, Hamish (9 October 2012). "Quantum-control pioneers bag 2012 Nobel Prize for Physics" . Physics World . London . Retrieved 2013-10-09 .
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