Tomas Opatrny

FAST CARS: Engineering a laser spectroscopic technique for rapid identification of bacterial spores

Airborne contaminants, e.g., bacterial spores, are usually analyzed by time-consuming microscopic, chemical, and biological assays. Current research into real-time laser spectroscopic detectors of such contaminants is based on e.g., resonance fluorescence. The present approach derives from recent experiments in which atoms and molecules are prepared by one (or more) coherent laser(s) and probed by another set of lasers. However, generating and using maximally coherent oscillation in macromolecules having an enormous number of degrees of freedom is challenging. In particular, the short dephasing times and rapid internal conversion rates are major obstacles. However, adiabatic fast passage techniques and the ability to generate combs of phase-coherent femtosecond pulses provide tools for the generation and utilization of maximal quantum coherence in large molecules and biopolymers. We call this technique FAST CARS (femtosecond adaptive spectroscopic techniques for coherent anti-Stokes Raman spectroscopy), and the present article proposes and analyses ways in which it could be used to rapidly identify preselected molecules in real time.

Towards a FAST-CARS anthrax detector: CARS generation in a DPA surrogate molecule

Abstract Coherent anti-Stokes Raman spectroscopy (CARS) has been investigated as a detection method for the identification of dipicolinic acid (DPA), a marker molecule for bacterial spores of anthrax. The laser dye molecule DCM was used as a surrogate molecule for DPA. In preliminary experiments, a molecular sensitivity was achieved in DCM that is projected to be sufficient to detect the DPA in bacterial spore clumps as small as 5.5 μm in diameter, small enough to be of interest in practical detection scenarios.

Spontaneous Raman spectra of dipicolinic acid in microcrystalline form

Abstract Dipicolinic acid (DPA) is an important component of bacterial spores. The Raman spectrum of DPA in the form of compacted powder was measured in reflection at room temperature with excitation by a nanosecond laser at 532 nm. The spectrum presents a set of characteristic frequency bands in the region 700–3090 cm−1 that were identified with characteristic vibrational modes of the DPA molecule.

Optimization approach to entanglement distillation

We put forward a method for optimized distillation of partly entangled pairs of qubits into a smaller number of more entangled pairs by recurrent local unitary operations and projections. Optimized distillation is achieved by minimization of a cost function with up to 30 real parameters, which is chosen to be sensitive to the fidelity and the projection probability at each step. We show that in many cases this approach can significantly improve the distillation efficiency in comparison to the present methods.