137,052 research outputs found
"Quantum Interference with Slits" Revisited
Marcella [arXiv:quant-ph/0703126] has presented a straightforward technique
employing the Dirac formalism to calculate single- and double-slit interference
patterns. He claims that no reference is made to classical optics or scattering
theory and that his method therefore provides a purely quantum mechanical
description of these experiments. He also presents his calculation as if no
approximations are employed. We show that he implicitly makes the same
approximations found in classical treatments of interference and that no new
physics has been introduced. At the same time, some of the quantum mechanical
arguments Marcella gives are, at best, misleading.Comment: 11 pages, 3 figure
Entanglement detection from interference fringes in atom-photon systems
A measurement scheme of atomic qubits pinned at given positions is studied by
analyzing the interference pattern obtained when they emit photons
spontaneously. In the case of two qubits, a well-known relation is revisited,
in which the interference visibility is equal to the concurrence of the state
in the infinite spatial separation limit of the qubits. By taking into account
the super-radiant and sub-radiant effects, it is shown that a state tomography
is possible when the qubit spatial separation is comparable to the wavelength
of the atomic transition. In the case of three qubits, the relations between
various entanglement measures and the interference visibility are studied,
where the visibility is defined from the two-qubit case. A qualitative
correspondence among these entanglement relations is discussed. In particular,
it is shown that the interference visibility is directly related to the maximal
bipartite negativity.Comment: 12 pages, 2 figures, published versio
Narrow resonances with excitation of finite bandwidth field
The effect of the laser linewidth on the resonance fluorescence spectrum of a
two-level atom is revisited. The novel spectral features, such as hole-burning
and dispersive profiles at line centre of the fluorescence spectrum are
predicted when the laser linewidth is much greater than its intensity. The
unique features result from quantum interference between different
dressed-state transition channels.Comment: 4 pages & 4 figures, Phys. Lett. A, (in press
Photon number conservation and photon interference
The group theoretical aspect of the description of passive lossless optical
four-ports (beam splitters) is revisited. It is shown through an example, that
this approach can be useful in understanding interferometric schemes where a
low number of photons interfere. The formalism is extended to passive lossless
optical six-ports, their SU(3)-theory is outlined.Comment: Contribution at "Classical and Quantum Interference" workshop in RCO,
Olomouc, Oct. 25-26 2001. A corrected versio
Syntactic Control of Interference Revisited
In Syntactic Control of Interference (POPL, 1978), J. C. Reynolds proposes three design principles intended to constrain the scope of imperative state effects in Algol-like languages. The resulting linguistic framework seems to be a very satisfactory way of combining functional and imperative concepts, having the desirable attributes of both purely functional languages (such as pcf) and simple imperative languages (such as the language of while programs). However, Reynolds points out that the obvious syntax for interference control has the unfortunate property that fi-reductions do not always preserve typings. Reynolds has subsequently presented a solution to this problem (ICALP, 1989), but it is fairly complicated and requires intersection types in the type system. Here, we present a much simpler solution which does not require intersection types. We first describe a new type system inspired in part by linear logic and verify that reductions preserve typings. We then define a class of bireflective models, which provide a categorical analysis of structure underlying the new typing rules; a companion paper Bireflectivity, in this volume, exposes wider ramifications of this structure. Finally, we describe a concrete model for an illustrative programming language based on the new type system; this improves on earlier such efforts in that states are not assumed to be structured using locations
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