Multimode optical parametric amplification in the phase-sensitive regime.

Phase-sensitive optical parametric amplification of squeezed states helps to overcome detection loss and noise and thus increases the robustness of sub-shot-noise sensing. Because such techniques, e.g., imaging and spectroscopy, operate with multimode light, multimode amplification is required. Here we find the optimal methods for multimode phase-sensitive amplification and verify them in an experiment where a pumped second-order nonlinear crystal is seeded with a Gaussian coherent beam. Phase-sensitive amplification is obtained by tightly focusing the seed into the crystal, rather than seeding with close-to-plane waves. This suggests that phase-sensitive amplification of sub-shot-noise images should be performed in the near field. A similar recipe can be formulated for the time and frequency, which makes this work relevant for quantum-enhanced spectroscopy.

[Verapamil versus flunarizine in the preventive therapy of hemicrania]. / Verapamil versus flunarizina nella terapia preventiva dell'emicrania.

In this single-blind, parallel group study, the efficacy of verapamil (240 mg/die) vs flunarizine (10 mg/die) for prophylactic treatment was evaluated in 38 patients (8M and 30F, mean age 34.4 years) with common or classic migraine. During the 3 months study, both drugs were found to be effective in reducing the number and intensity of the attacks. Verapamil showed better safety than flunarizine.