119 research outputs found
Generating Polarization-Entangled Photon Pairs with Arbitrary Joint Spectrum
We present a scheme for generating polarization-entangled photons pairs with
arbitrary joint spectrum. Specifically, we describe a technique for spontaneous
parametric down-conversion in which both the center frequencies and the
bandwidths of the down-converted photons may be controlled by appropriate
manipulation of the pump pulse. The spectral control offered by this technique
permits one to choose the operating wavelengths for each photon of a pair based
on optimizations of other system parameters (loss in optical fiber, photon
counter performance, etc.). The combination of spectral control, polarization
control, and lack of group-velocity matching conditions makes this technique
particularly well-suited for a distributed quantum information processing
architecture in which integrated optical circuits are connected by spans of
optical fiber.Comment: 6 pages, 3 figure
Synthesis and Analysis of Entangled Photonic Qubits in Spatial-Parity Space
We present the novel embodiment of a photonic qubit that makes use of one
continuous spatial degree of freedom of a single photon and relies on the the
parity of the photon's transverse spatial distribution. Using optical
spontaneous parametric downconversion to produce photon pairs, we demonstrate
the controlled generation of entangled-photon states in this new space.
Specifically, two Bell states, and a continuum of their superpositions, are
generated by simple manipulation of a classical parameter, the optical-pump
spatial parity, and not by manipulation of the entangled photons themselves. An
interferometric device, isomorphic in action to a polarizing beam splitter,
projects the spatial-parity states onto an even--odd basis. This new physical
realization of photonic qubits could be used as a foundation for future
experiments in quantum information processing.Comment: 6 pages, 5 figures, submitted to PR
Symmetric Autocompensating Quantum Key Distribution
We present quantum key distribution schemes which are autocompensating
(require no alignment) and symmetric (Alice and Bob receive photons from a
central source) for both polarization and time-bin qubits. The primary benefit
of the symmetric configuration is that both Alice and Bob may have passive
setups (neither Alice nor Bob is required to make active changes for each run
of the protocol). We show that both the polarization and the time-bin schemes
may be implemented with existing technology. The new schemes are related to
previously described schemes by the concept of advanced waves.Comment: 4 pages, 2 figur
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