15,391 research outputs found
Steady-state phase error for a phase-locked loop subjected to periodic Doppler inputs
The performance of a carrier phase locked loop (PLL) driven by a periodic Doppler input is studied. By expanding the Doppler input into a Fourier series and applying the linearized PLL approximations, it is easy to show that, for periodic frequency disturbances, the resulting steady state phase error is also periodic. Compared to the method of expanding frequency excursion into a power series, the Fourier expansion method can be used to predict the maximum phase error excursion for a periodic Doppler input. For systems with a large Doppler rate fluctuation, such as an optical transponder aboard an Earth orbiting spacecraft, the method can be applied to test whether a lower order tracking loop can provide satisfactory tracking and thereby save the effect of a higher order loop design
Quantum correlation in degenerate optical parametric oscillators with mutual injections
We theoretically and numerically study the quantum dynamics of two degenerate
optical parametric oscillators with mutual injections. The cavity mode in the
optical coupling path between the two oscillator facets is explicitly
considered. Stochastic equations for the oscillators and mutual injection path
based on the positive representation are derived. The system of two
gradually pumped oscillators with out-of-phase mutual injections is simulated,
and its quantum state is investigated. When the incoherent loss of the
oscillators other than the mutual injections is small, the squeezed quadratic
amplitudes in the oscillators are positively correlated near the
oscillation threshold. It indicates finite quantum correlation, estimated via
Gaussian quantum discord, and the entanglement between the intracavity
subharmonic fields. When the loss in the injection path is low, each oscillator
around the phase transition point forms macroscopic superposition even under a
small pump noise. It suggests that the squeezed field stored in the low-loss
injection path weakens the decoherence in the oscillators.Comment: 14 pages, 9 figures; v3: author added, minor updat
Qubit-Programmable Operations on Quantum Light Fields
Engineering quantum operations is one of the main abilities we need for
developing quantum technologies and designing new fundamental tests. Here we
propose a scheme for realising a controlled operation acting on a travelling
quantum field, whose functioning is determined by an input qubit. This study
introduces new concepts and methods in the interface of continuous- and
discrete-variable quantum optical systems.Comment: Comments welcom
Perturbed and Permuted: Signal Integration in Network-Structured Dynamic Systems
Biological systems (among others) may respond to a large variety of distinct
external stimuli, or signals. These perturbations will generally be presented
to the system not singly, but in various combinations, so that a proper
understanding of the system response requires assessment of the degree to which
the effects of one signal modulate the effects of another. This paper develops
a pair of structural metrics for sparse differential equation models of complex
dynamic systems and demonstrates that said metrics correlate with proxies of
the susceptibility of one signal-response to be altered in the context of a
second signal. One of these metrics may be interpreted as a normalized arc
density in the neighborhood of certain influential nodes; this metric appears
to correlate with increased independence of signal response
Aspects of nonlocality in atom-photon interactions in a cavity
We investigate a Bell-type inequality for probabilities of detected atoms
formulated using atom-photon interactions in a cavity. We consider decoherence
brought about by both atomic decay, as well as cavity photon loss, and study
its quantitative action in diminishing the atom-field and the resultant
atom-atom secondary correlations. We show that the effects of decoherence on
nonlocality can be observed in a controlled manner in actual experiments
involving the micromaser and also the microlaser.Comment: 9 pages, 3 .eps figures, Revtex. Revised version with details of
calculations and more result
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