16,809 research outputs found
Quantum simulation of zero temperature quantum phases and incompressible states of light via non-Markovian reservoir engineering techniques
We review recent theoretical developments on the stabilization of strongly
correlated quantum fluids of light in driven-dissipative photonic devices
through novel non-Markovian reservoir engineering techniques. This approach
allows to compensate losses and refill selectively the photonic population so
to sustain a desired steady-state. It relies in particular on the use of a
frequency-dependent incoherent pump which can be implemented, e.g., via
embedded two-level systems maintained at a strong inversion of population. As
specific applications of these methods, we discuss the generation of Mott
Insulator (MI) and Fractional Quantum Hall (FQH) states of light. As a first
step, we present the case of a narrowband emission spectrum and show how this
allows for the stabilization of MI and FQH states under the condition that the
photonic states are relatively flat in energy. As soon as the photonic
bandbwidth becomes comparable to the emission linewidth, important
non-equilibrium signatures and entropy generation appear. As a second step, we
review a more advanced configuration based on reservoirs with a broadband
frequency distribution, and we highlight the potential of this configuration
for the quantum simulation of equilibrium quantum phases at zero temperature
with tunable chemical potential. As a proof of principle we establish the
applicability of our scheme to the Bose-Hubbard model by confirming the
presence of a perfect agreement with the ground-state predictions both in the
Mott Insulating and superfluid regions, and more generally in all parts of the
parameter space. Future prospects towards the quantum simulation of more
complex configurations are finally outlined, along with a discussion of our
scheme as a concrete realization of quantum annealing
Putting energy back in control
A control system design technique using the principle of energy balancing was analyzed. Passivity-based control (PBC) techniques were used to analyze complex systems by decomposing them into simpler sub systems, which upon interconnection and total energy addition were helpful in determining the overall system behavior. An attempt to identify physical obstacles that hampered the use of PBC in applications other than mechanical systems was carried out. The technique was applicable to systems which were stabilized with passive controllers
On the Selection of Tuning Methodology of FOPID Controllers for the Control of Higher Order Processes
In this paper, a comparative study is done on the time and frequency domain
tuning strategies for fractional order (FO) PID controllers to handle higher
order processes. A new fractional order template for reduced parameter modeling
of stable minimum/non-minimum phase higher order processes is introduced and
its advantage in frequency domain tuning of FOPID controllers is also
presented. The time domain optimal tuning of FOPID controllers have also been
carried out to handle these higher order processes by performing optimization
with various integral performance indices. The paper highlights on the
practical control system implementation issues like flexibility of online
autotuning, reduced control signal and actuator size, capability of measurement
noise filtration, load disturbance suppression, robustness against parameter
uncertainties etc. in light of the above tuning methodologies.Comment: 27 pages, 10 figure
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