303,185 research outputs found
On the significance of a recent experiment demonstrating quantum interference in time
I comment on the interpretation of a recent experiment showing quantum
interference in time. It is pointed out that the standard nonrelativistic
quantum theory, used by the authors in their analysis, cannot account for the
results found, and therefore that this experiment has fundamental importance
beyond the technical advances it represents. Some theoretical structures which
consider the time as an observable, and thus could, in principle, have the
required coherence in time, are discussed briefly, and the application of
Floquet theory and the manifestly covariant quantum theory of Stueckelberg are
treated in some detail. In particular, the latter is shown to account for the
results in a simple and consistent way.Comment: 10 pages, plain TeX. Revision for clarity, reference to other
candidate theorie
Solid-state quantum optics with quantum dots in photonic nanostructures
Quantum nanophotonics has become a new research frontier where quantum optics
is combined with nanophotonics in order to enhance and control the interaction
between strongly confined light and quantum emitters. Such progress provides a
promising pathway towards quantum-information processing on an all-solid-state
platform. Here we review recent progress on experiments with single quantum
dots in nanophotonic structures. Embedding the quantum dots in photonic
band-gap structures offers a way of controlling spontaneous emission of single
photons to a degree that is determined by the local light-matter coupling
strength. Introducing defects in photonic crystals implies new functionalities.
For instance, efficient and strongly confined cavities can be constructed
enabling cavity-quantum-electrodynamics experiments. Furthermore, the speed of
light can be tailored in a photonic-crystal waveguide forming the basis for
highly efficient single-photon sources where the photons are channeled into the
slowly propagating mode of the waveguide. Finally, we will discuss some of the
surprises that arise in solid-state implementations of quantum-optics
experiments in comparison to their atomic counterparts. In particular, it will
be shown that the celebrated point-dipole description of light-matter
interaction can break down when quantum dots are coupled to plasmon
nanostructures.Comment: Review. 15 pages, 9 figure
Generalized Quantum Theory: Overview and Latest Developments
The main formal structures of Generalized Quantum Theory are summarized.
Recent progress has sharpened some of the concepts, in particular the notion of
an observable, the action of an observable on states (putting more emphasis on
the role of proposition observables), and the concept of generalized
entanglement. Furthermore, the active role of the observer in the structure of
observables and the partitioning of systems is emphasized.Comment: 14 pages, update in reference
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