Introduction to Focus Issue: nonlinear and stochastic physics in biology

Frank Moss was a leading figure in the study of nonlinear and stochastic processes in biological systems. His work, particularly in the area of stochastic resonance, has been highly influential to the interdisciplinary scientific community. This Focus Issue pays tribute to Moss with articles that describe the most recent advances in the field he helped to create. In this Introduction, we review Moss's seminal scientific contributions and introduce the articles that make up this Focus Issue.     

Hyperentanglement source by intersubband two-photon emission from semiconductor quantum wells

We propose an efficient hyperentanglement source emitting photon pairs entangled in both energy and polarization. The compact electrically driven room-temperature source, based on intersubband two-photon emission from semiconductor quantum wells (QWs) exhibits pair generation rates several orders of magnitude higher than alternative conventional schemes. A theoretical formalism is derived for the calculation of photon pair generation spectra and rates. The results are presented for superlattice structures similar to quantum cascade lasers of GaAs/AlGaAs QWs emitting in the mid-IR and far-IR and for InN/AlN QW structures suitable for telecommunication wavelengths.     

Measurement of the quadrupole moments of the first 2+ states of 130Ba and 134Ba

The quadrupole moments of the first 2⁺ states of ^130,134Ba were measured using the reorientation precession technique. Prolate deformations were determined for both nuclei. The quadrupole moments found were Q = ?0.33 ± 0.24 b and ?0.31 ± 0.24 b for ¹³⁰Ba and ¹³⁴Ba, respectively.