1,721,028 research outputs found
Spatio–temporal entanglement of twin photons: An intuitive picture
No full textWe draw an intuitive picture of the spatio–temporal properties of the entangled state of twin
photons, where they are described as classical wave-packets. This picture predicts a precise
relation between their temporal and transverse spatial separations at the crystal output. The
space-time coupling described by classical arguments turns out to determine in a precise way the
spatio–temporal structure of the quantum entanglement, analyzed by means of the biphotonic
correlation and of the Schmidt dimensionality of the entanglement
Enhancing upconversion with space–time entanglement: from twin photons to twin-beams
No full textWe investigate the use of entangled photons generated by parametric downconversion to improve the efficiency of second harmonic generation (SHG). Using a fully three-dimensional model for the nonlinear interactions, we obtain quantitative predictions of the efficiency of quantum-enhanced SHG and identify the critical parameters to optimize the process. By a careful control of the spatial and temporal degrees of freedom, we demonstrate a robust quantum advantage, extending to illumination fluxes well above the limits traditionally considered in the literature. Our analysis offers valuable insights into the ongoing debate on quantum-enhanced two-photon processes and helps establish their usefulness in applications
Heralding pure single photons: A comparison between counterpropagating and copropagating twin photons
No full textWe investigate different strategies suitable to generate pure heralded single photons through spontaneous parametric down-conversion, comparing the counterpropagating geometry with more conventional copropagating configurations which enhance the purity of the heralded photon state through the technique of group-velocity matching. We derive general results for the Schmidt number associated to the temporal modes, which provide a quantitative estimate of the purity. An analysis of the correlation of twin photons in the temporal domain provides a more physical view of the mechanisms that permit to eliminate the temporal entanglement of the state and to generate high-purity heralded photons. The efficiency of the various strategies and the individual properties of the heralded photons thereby generated are then compared
Entangled imaging in the large photon number regime
No full textWe formulate a theory for entangled imaging that includes the case of a large number of photons in
the two entangled beams. We show that the results for imaging and the wave–particle duality features, which
have been demonstrated in the microscopic case, persist in the macroscopic domain. Although the visibility of
the information retrieved via correlation measurements in the regime of a high number of photons is lower than
in the coincidence counting regime, we show that efficient reconstruction of both the image and the diffraction
pattern of an object is possibl
Optical pattern formation
No full textThis chapter focuses on the concept of optical pattern formation. The field of optical pattern formation (OPF) studies the spatial and spatiotemporal phenomena that arise in the structure of electromagnetic field in the planes orthogonal with respect to the direction of propagation. Most theoretical treatments of the interaction between matter and radiation introduce the plane wave approximation—that is, they assume that the electric field is uniform in each transverse plane. However, the field of OPF studies mainly the interaction with nonlinear media, where the phenomena emerge spontaneously as a consequence of an instability; another name that is commonly used to designate OPF is “transverse nonlinear optics.” Historically, the broad interest in OPF emerged as a natural evolution of the previous development of the field of optical instabilities and chaos, when the main attention shifted gradually from purely temporal effects to spatio-temporal phenomena. For both the fields of optical instabilities and OPF, continuous inspiration arose from the formulation of general disciplines as Haken's synergetics or Prigogine's theory of dissipative structures
Tailoring the spatiotemporal structure of biphoton entanglement in type-I parametric down-conversion
No full textWe investigate the spatiotemporal structure of the biphoton entangled state produced by parametric down-conversion (PDC) at the output face of the nonlinear crystal. We analyze the geometry of biphoton correlation for different gain regimes (from ultralow to high), different crystal lengths, and different tuning angles of the crystal. While for collinear or quasicollinear phase matching a X-shaped geometry, nonfactorizable in space and time, dominates, in the highly noncollinear conditions we observe a remarkable transition to a factorizable geometry. We show that the geometry of spatiotemporal correlation is a consequence of the angle-frequency relationship imposed by phase matching and that the fully spatiotemporal analysis provides a key to control the spatiotemporal properties of the PDC entangled state and in particular to access a biphoton localization in time and space in the femtosecond and micrometer range, respectively
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Squeezing and Einstein-Podolsky-Rosen correlation in the mirrorless optical parametric oscillator
No full textThis work analyses the quantum properties of counterpropagating twin beams generated by a mirrorless optical parametric oscillator in the continuous-variable regime. Despite the lack of the filtering effect of a cavity, we show that in the vicinity of its threshold it may generate high levels of narrowband squeezing and Einstein-Podolsky-Rosen correlation, completely comparable to what can be obtained in standard optical parametric oscillators
- …
