Frequency down conversion through Bose condensation of light

We propose an experimental set up allowing to convert an input light of wavelengths about $1-2 \mu m$ into an output light of a lower frequency. The basic principle of operating relies on the nonlinear optical properties exhibited by a microcavity filled with glass. The light inside this material behaves like a 2D interacting Bose gas susceptible to thermalise and create a quasi-condensate. Extension of this setup to a photonic bandgap material (fiber grating) allows the light to behave like a 3D Bose gas leading, after thermalisation, to the formation of a Bose condensate. Theoretical estimations show that a conversion of $1 \mu m$ into $1.5 \mu m$ is achieved with an input pulse of about $1 ns$ with a peak power of $10^3 W$, using a fiber grating containing an integrated cavity of size about $500 \mu m \times 100 \mu m^2$.Comment: 4 pages, 1 figure

Dynamic generation of maximally entangled photon multiplets by adiabatic passage

The adiabatic passage scheme for quantum state synthesis, in which atomic Zeeman coherences are mapped to photon states in an optical cavity, is extended to the general case of two degenerate cavity modes with orthogonal polarization. Analytical calculations of the dressed-state structure and Monte Carlo wave-function simulations of the system dynamics show that, for a suitably chosen cavity detuning, it is possible to generate states of photon multiplets that are maximally entangled in polarization. These states display nonclassical correlations of the type described by Greenberger, Horne, and Zeilinger (GHZ). An experimental scheme to realize a GHZ measurement using coincidence detection of the photons escaping from the cavity is proposed. The correlations are found to originate in the dynamics of the adiabatic passage and persist even if cavity decay and GHZ state synthesis compete on the same time scale. Beyond entangled field states, it is also possible to generate entanglement between photons and the atom by using a different atomic transition and initial Zeeman state.Comment: 22 pages (RevTeX), including 23 postscript figures. To be published in Physical Review

Rotational master equation for cold laser-driven molecules

The equations of motion for the molecular rotation are derived for vibrationally cold dimers that are polarized by off-resonant laser light. It is shown that, by eliminating electronic and vibrational degrees of freedom, a quantum master equation for the reduced rotational density operator can be obtained. The coherent rotational dynamics is caused by stimulated Raman transitions, whereas spontaneous Raman transitions lead to decoherence in the motion of the quantized angular momentum. As an example the molecular dynamics for the optical Kerr effect is chosen, revealing decoherence and heating of the molecular rotation.Comment: 11 pages, 5 figures, to appear in Phys. Rev.

Coherent dynamics of Bose-Einstein condensates in high-finesse optical cavities

We study the mutual interaction of a Bose-Einstein condensed gas with a single mode of a high-finesse optical cavity. We show how the cavity transmission reflects condensate properties and calculate the self-consistent intra-cavity light field and condensate evolution. Solving the coupled condensate-cavity equations we find that while falling through the cavity, the condensate is adiabatically transfered into the ground state of the periodic optical potential. This allows time dependent non-destructive measurements on Bose-Einstein condensates with intriguing prospects for subsequent controlled manipulation.Comment: 5 pages, 5 figures; revised version: added reference

What the public think about participation in medical research during an influenza pandemic: an international cross-sectional survey

Objectives The public and patients are primary contributors and beneficiaries of pandemic-relevant clinical research. However, their views on research participation during a pandemic have not been systematically studied. We aimed to understand public views regarding participation in clinical research during a hypothetical influenza pandemic. Study design This is an international cross-sectional survey. Methods We surveyed the views of nationally representative samples of people in Belgium, Poland, Spain, Ireland, the United Kingdom, Canada, Australia and New Zealand, using a scenario-based instrument during the 2017 regional influenza season. Descriptive and regression analyses were conducted. Results Of the 6804 respondents, 5572 (81.8%) thought pandemic-relevant research was important, and 5089 (74.8%) thought ‘special rules’ should be applied to make this research feasible. The respondents indicated willingness to take part in lower risk (4715, 69.3%) and higher risk (3585, 52.7%) primary care and lower risk (4780, 70.3%) and higher risk (4113, 60.4%) intensive care unit (ICU) study scenarios. For primary care studies, most (3972, 58.4%) participants preferred standard enrolment procedures such as prospective written informed consent, but 2327 (34.2%) thought simplified procedures would be acceptable. For ICU studies, 2800 (41.2%) preferred deferred consent, and 2623 (38.6%) preferred prospective third-party consent. Greater knowledge about pandemics, trust in a health professional, trust in the government, therapeutic misconception and having had ICU experience as a patient or carer predicted increased willingness to participate in pandemic-relevant research. Conclusions Our study indicates current public support for pandemic-relevant clinical research. Tailored information and initiatives to advance research literacy and maintain trust are required to support pandemic-relevant research participation and engagement