Continuous measurement feedback control of a Bose-Einstein condensate using phase contrast imaging

We consider the theory of feedback control of a Bose-Einstein condensate (BEC) confined in a harmonic trap under a continuous measurement constructed via non-destructive imaging. A filtering theory approach is used to derive a stochastic master equation (SME) for the system from a general Hamiltonian based upon system-bath coupling. Numerical solutions for this SME in the limit of a single atom show that the final steady state energy is dependent upon the measurement strength, the ratio of photon kinetic energy to atomic kinetic energy, and the feedback strength. Simulations indicate that for a weak measurement strength, feedback can be used to overcome heating introduced by the scattering of light, thereby allowing the atom to be driven towards the ground state.Comment: 4 figures, 11 page

Use of conductimetric technique for data capture in predictive microbiology

Conductimetry as an alternative data capture method for following microbial growth has a great potential as a research tool of predictive microbiology. In spite of this fact there is only a limited number of applications using conductimetric data for model generation. In this study the growth of single strains of Listeria monocytogenes and Lactococcus lactis was tested in 5 media using a RABITinstrument. The goal of the work was to find selective growth media for Listeria and Lactococcus, respectively, in order to study their interaction in mixed-culture using the conductimetric technique. Whitley Anaerobic broth, Whitley Impedance broth and modified Whitely Impedance broth (Whitley Impedance broth + Chloramphenicol 7 mg l Ś1) were not suitable for following selectively the growth of Lactococcus lactis or Listeria monocytogenes in a mixed culture of the two bacteria. BiMedia 630 A for Lactococcus lactis and Bimedia 403 A for Listeria monocytogenes satisfied the demands raised by conductance measurement. Linear correlations were established between the graphically estimated TTD values of the conductance curves and the logarithmic numbers of colony forming units (CFU). The correlations were very strong in each case (determination coefficients (R 2) of the linear regression were higher than 0.98 at both medium-strain combinations). However, in BiMedia 630 Listeria monocytogenes was capable of slow growth, therefore, this medium would be feasible for studying microbial interactions if only low concentrations of Listeria (less than 10 6 CFU ml Ś1) were present in the mixed culture

Controlling chaos in the quantum regime using adaptive measurements

The continuous monitoring of a quantum system strongly influences the emergence of chaotic dynamics near the transition from the quantum regime to the classical regime. Here we present a feedback control scheme that uses adaptive measurement techniques to control the degree of chaos in the driven-damped quantum Duffing oscillator. This control relies purely on the measurement backaction on the system, making it a uniquely quantum control, and is only possible due to the sensitivity of chaos to measurement. We quantify the effectiveness of our control by numerically computing the quantum Lyapunov exponent over a wide range of parameters. We demonstrate that adaptive measurement techniques can control the onset of chaos in the system, pushing the quantum-classical boundary further into the quantum regime

Robustness of System-Filter Separation for the Feedback Control of a Quantum Harmonic Oscillator Undergoing Continuous Position Measurement

We consider the effects of experimental imperfections on the problem of estimation-based feedback control of a trapped particle under continuous position measurement. These limitations violate the assumption that the estimator (i.e. filter) accurately models the underlying system, thus requiring a separate analysis of the system and filter dynamics. We quantify the parameter regimes for stable cooling, and show that the control scheme is robust to detector inefficiency, time delay, technical noise, and miscalibrated parameters. We apply these results to the specific context of a weakly interacting Bose-Einstein condensate (BEC). Given that this system has previously been shown to be less stable than a feedback-cooled BEC with strong interatomic interactions, this result shows that reasonable experimental imperfections do not limit the feasibility of cooling a BEC by continuous measurement and feedback.Comment: 14 pages, 8 figure

A rapid and sensitive method for the determination of high-fructose corn syrup (HFCS) in honey

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Evidence

Original writing. Three detective stories