Leno M. Pedrotti

Analysis of imperfect polarizer effects in magnetic rotation spectroscopy

Small amounts of ellipticity in the nominally linearly polarized light used in magnetic rotation spectroscopy play an important role in determining the character of the signals developed in these experiments. For example, ellipticity introduced by stress-induced birefringence can easily influence such signals more than does a nonzero polarizer extinction ratio. In addition, for nearly-crossed polarizers, an initial ellipticity allows one to probe magnetic circular dichroism instead of the more commonly investigated magnetic circular birefringence. A general expression for the magnetic rotation spectroscopy signal is derived and compared to experimental results. An expression for the detection sensitivity is developed by taking shot noise and rms laser power uctuations to be the dominant noise sources.

Theory of photon coincidence statistics in photon-correlated beams

The statistics of photon coincidence counting in photon-correlated beams is thoroughly investigated considering the effect of the finite coincidence resolving time. The correlated beams are assumed to be generated using parametric downconversion, and the photon streams in the correlated beams are modeled by two partially correlated Poisson point processes. An exact expression for the mean rate of coincidence registration is developed using techniques from renewal theory. It is shown that the use of the traditional approximate rate, in certain situations, leads to the overestimation of the actual rate. The error between the exact and approximate coincidence rates increases as the coincidence-noise parameter, defined as the mean number of uncorrelated photons detected per coincidence resolving time, increases. The use of the exact statistics of the coincidence becomes crucial when the background noise is high or in cases when high precision measurement of coincidence is required. Such cases arise whenever the coincidence-noise parameter is even slightly in excess of zero. It is also shown that the probability distribution function of the time between consecutive coincidence registration can be well approximated by an exponential distribution function. The well-known and experimentally verified Poissonian model of the coincidence registration process is therefore theoretically justified. The theory is applied to an on-off keying communication system proposed by Mandel which has been shown to perform well in extremely noisy conditions. It is shown that the bit-error rate (BER) predicted by the approximate coincidence-rate theory can be significantly lower than the actual BER obtained using the exact theory.

Spectra of single-atom lasers

We calculate the output spectrum of a single-atom laser in a microcavity across a wide range of operating conditions. We considered both three-level and four-level atomic level structures. We used a numerical routine to calculate spectra that is more efficient than others used previously. We found that the linewidth of a single-atom laser generally scales as the inverse of the photon number and that there is no pump value at which an abrupt change occurs that might locate a lasing threshold. For a three-level gain atom we found vacuum–Rabi splitting similar to that found by Loffler et al. [Phys. Rev. A 55, 3923 (1997)] and used quantum trajectory theory to obtain a new interpretation of the results. For a four-level gain atom the vacuum–Rabi structure can appear at a small nonzero pump level and is maintained for large pumps, even when the intracavity photon number is larger than unity and the laser is on. We use the quantum trajectory approach to explain these results.

Theoertical investigation of quantum waveform shaping for single photon emitters.

We investigate a new technique for quantum-compatible waveform shaping that extends the time lens method, and relies only on phase operations. Under realistic experimental conditions, we show that it is possible to both temporally compress and shape optical waveforms in the nanosecond to tens of picoseconds range, which is generally difficult to achieve using standard dispersive pulse-shaping techniques.

Atom-field entanglement in cavity QED: Nonlinearity and saturation

We investigate the degree of entanglement between an atom and a driven cavity mode, in the presence of dissipation. Previous work has shown that in the limit of weak driving fields, the steady state entanglement is proportional to the square of the driving intensity. This quadratic dependence is due to the generation of entanglement by the creation of pairs of photons/excitations. In this work we investigate the entanglement between an atom and a cavity in the presence of multiple photons. Nonlinearity of the atomic response is needed to generate entanglement, but as that nonlinearity saturates the entanglement vanishes. We posit that this is due to spontaneous emission, which puts the atom in the ground state and the atom-field state into a direct product state. An intermediate value of the driving field, near the field that saturates the atomic response, optimizes the atom-field entanglement. In a parameter regime for which multiphoton resonances occur, we find that entanglement recurs at those resonances. \\cite{Shamailov-10} In this regime, we find that the entanglement decreases with increaing photon number. We also investigate, in the bimodal regime of Alsing et. al.\cite{Alsing-91-DressedState} \cite{Alsing-92-DSS}\\cite{Carm-15-X}, the entanglement as a function of atom and/or cavity detuning. Here we find that there is evidence of a phase transition in the entanglement, which occurs at

Quantum Interference in the Incoherent Spectra of Resonance Fluorescence

2\epsilon/g \geq 1

Laser Probes Of General Relativity

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Bell’S Theorem and Quasiclassical Quantum Distribution Theory: A Calculational Example

The incoherent spectrum of resonance fluorescence is a Lorentzian squared instead of the usual Lorentzian. We explain this as a quantum interference effect using quantum trajectory theory.

Introduction to Optics

Probes of general relativity which hinge upon the use of the laser are discussed and interpreted. Some background involving pre-laser tests of general relativity are briefly discussed to indicate the scarcity of such tests.

Treatment of the spectrum of squeezing based on the modes of the universe. I. Theory and a physical picture

A simple proof of Bell’s Theorem is developed by considering the Einstein, Rosen, Podolski and Bohm spin singlet gedanken-experiment. The quantum mechanical violation of Bell’s Theorem for this set-up is developed using the formalism of quasiclassical quantum distribution theory. This formalism allows one to easily note the difference, in this simple case, between quantum mechanics and the sort of theories which satisfy the Bell inequality.