401 research outputs found
Multimode Hong-Ou-Mandel interference
We consider multimode two-photon interference at a beam splitter by photons
created by spontaneous parametric down-conversion. The resulting interference
pattern is shown to depend upon the transverse spatial symmetry of the pump
beam. In an experiment, we employ the first-order Hermite-Gaussian modes in
order to show that, by manipulating the pump beam, one can control the
resulting two-photon interference behavior. We expect these results to play an
important role in the engineering of quantum states of light for use in quantum
information processing and quantum imaging.Comment: 4 pages, 6 figures, submitted to PR
Optical Bell-state analysis in the coincidence basis
Many quantum information protocols require a Bell-state measurement of
entangled systems. Most optical Bell-state measurements utilize two-photon
interference at a beam splitter. By creating polarization-entangled photons
with spontaneous parametric down-conversion using a first-order
Hermite-Gaussian pump beam, we invert the usual interference behavior and
perform an incomplete Bell-state measurement in the coincidence basis. We
discuss the possibility of a complete Bell-state measurement in the coincidence
basis using hyperentangled states [Phys. Rev. A, \textbf{58}, R2623 (1998)].Comment: 5 pages, 5 figure
Quantum communication without alignment using multiple-qubit single-photon states
We propose a scheme for encoding logical qubits in a subspace protected
against collective rotations around the propagation axis using the polarization
and transverse spatial degrees of freedom of single photons. This encoding
allows for quantum key distribution without the need of a shared reference
frame. We present methods to generate entangled states of two logical qubits
using present day down-conversion sources and linear optics, and show that the
application of these entangled logical states to quantum information schemes
allows for alignment-free tests of Bell's inequalities, quantum dense coding
and quantum teleportation
Spatial correlations in parametric down-conversion
The transverse spatial effects observed in photon pairs produced by
parametric down-conversion provide a robust and fertile testing ground for
studies of quantum mechanics, non-classical states of light, correlated imaging
and quantum information. Over the last 20 years there has been much progress in
this area, ranging from technical advances and applications such as quantum
imaging to investigations of fundamental aspects of quantum physics such as
complementarity relations, Bell's inequality violation and entanglement. The
field has grown immensely: a quick search shows that there are hundreds of
papers published in this field. The objective of this article is to review the
building blocks and major theoretical and experimental advances in the field,
along with some possible technical applications and connections to other
research areas.Comment: 116 pages, 35 figures. To appear in Physics Report
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