3,909 research outputs found
Why you should not use the electric field to quantize in nonlinear optics
We show that using the electric field as a quantization variable in nonlinear
optics leads to incorrect expressions for the squeezing parameters in
spontaneous parametric down-conversion and conversion rates in frequency
conversion. This observation is related to the fact that if the electric field
is written as a linear combination of bosonic creation and annihilation
operators one cannot satisfy Maxwell's equations in a nonlinear dielectric.Comment: This version corrects a minor typo from the published version in
Optics Letters. Eq. 22 should have an \epsilon_0 that is lacking in the OL
versio
High efficiency in mode selective frequency conversion
Frequency conversion (FC) is an enabling process in many quantum information
protocols. Recently, it has been observed that upconversion efficiencies in
single-photon, mode-selective FC are limited to around 80%.In this letter we
argue that these limits can be understood as time-ordering corrections (TOCs)
that modify the joint conversion amplitude of the process. Furthermore we show,
using a simple scaling argument, that recently proposed cascaded FC protocols
that overcome the aforementioned limitations act as "attenuators" of the TOCs.
This observation allows us to argue that very similar cascaded architectures
can be used to attenuate TOCs in photon generation via spontaneous parametric
down-conversion. Finally, by using the Magnus expansion, we argue that the
TOCs, which are usually considered detrimental for FC efficiency, can also be
used to increase the efficiency of conversion in partially mode selective FC
Mentoring School-Age Children: A Classification of Programs
The number of mentoring programs providing adult support to youth has increased dramatically in recent years. This report presents information on the characteristics of programs serving school-aged youth (K-12). We found that rather than simply replicating the traditional Big Brothers Big Sisters model, newer programs are emphasizing somewhat more instrumental goals and activities, as well as experimenting with different types of relationships (group, school-based, etc.). Most programs seem to have sufficient infrastructure to screen, train, and supervise their mentors adequately, but many de-emphasize the importance of developing long-term relationships
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