Effect of atomic beam alignment on photon correlation measurements in cavity QED

Quantum trajectory simulations of a cavity QED system comprising an atomic beam traversing a standing-wave cavity are carried out. The delayed photon coincident rate for forwards scattering is computed and compared with the measurements of Rempe et al. [Phys. Rev. Lett. 67, 1727 (1991)] and Foster et al. [Phys. Rev. A 61, 053821 (2000)]. It is shown that a moderate atomic beam misalignment can account for the degradation of the predicted correlation. Fits to the experimental data are made in the weak-field limit with a single adjustable parameter--the atomic beam tilt from perpendicular to the cavity axis. Departures of the measurement conditions from the weak-field limit are discussed.Comment: 15 pages and 13 figure

The Epidemiology of Skin Cancer in Queensland: The Significance of Premalignant Conditions

Data are presented for four cities in Quensland that show that there is a tendency for both basal and squamous cell cancer to occur in the absence of hyperkeratosis. The converse also holds. The anatomical distribution of the keratoses does not follow that of one particular form of cancer, but roughly that of both, although basal cell cancers and hyperkeratoses are not likely to be confused clinically. It seems that solar keratosis is not an important premalignant lesion, but rather that it occurs independently. In this, as in the preceding paper on the incidence of skin cancer, it must be stressed that geographical factors are specially important, and that what is true for Queensland is not necessarily true for other regions further from the Equator. This work was carried out during the tenure of a Medical Research Fellowship at the University of Queensland. I would like to acknowledge the advice and help of Dr. A. G. S. Cooper, Director of the Queensland Radium Institute

Atom detection in a two-mode optical cavity with intermediate coupling: Autocorrelation studies

We use an optical cavity in the regime of intermediate coupling between atom and cavity mode to detect single moving atoms. Degenerate polarization modes allow excitation of the atoms in one mode and collection of spontaneous emission in the other, while keeping separate the two sources of light; we obtain a higher confidence and efficiency of detection by adding cavity-enhanced Faraday rotation. Both methods greatly benefit from coincidence detection of photons, attaining fidelities in excess of 99% in less than 1 microsecond. Detailed studies of the second-order intensity autocorrelation function of light from the signal mode reveal evidence of antibunched photon emissions and the dynamics of single-atom transits.Comment: 10 pages, 10 figures, to be published in Phys. Rev.

From quantum feedback to probabilistic error correction: Manipulation of quantum beats in cavity QED

It is shown how to implement quantum feedback and probabilistic error correction in an open quantum system consisting of a single atom, with ground- and excited-state Zeeman structure, in a driven two-mode optical cavity. The ground state superposition is manipulated and controlled through conditional measurements and external fields, which shield the coherence and correct quantum errors. Modeling of an experimentally realistic situation demonstrates the robustness of the proposal for realization in the laboratory

Nonlinear photon transport in a semiconductor waveguide-cavity system containing a single quantum dot: Anharmonic cavity-QED regime

We present a semiconductor master equation technique to study the input/output characteristics of coherent photon transport in a semiconductor waveguide-cavity system containing a single quantum dot. We use this approach to investigate the effects of photon propagation and anharmonic cavity-QED for various dot-cavity interaction strengths, including weakly-coupled, intermediately-coupled, and strongly-coupled regimes. We demonstrate that for mean photon numbers much less than 0.1, the commonly adopted weak excitation (single quantum) approximation breaks down, even in the weak coupling regime. As a measure of the anharmonic multiphoton-correlations, we compute the Fano factor and the correlation error associated with making a semiclassical approximation. We also explore the role of electron--acoustic-phonon scattering and find that phonon-mediated scattering plays a qualitatively important role on the light propagation characteristics. As an application of the theory, we simulate a conditional phase gate at a phonon bath temperature of $20$K in the strong coupling regime.Comment: To appear in PR

Principles of War and Their Application to Strategy and Tactics

The task of the Naval War College mission is to further an understanding of the fundamentals of warfare, with. emphasis on their application to future naval warfare. Accordingly, it is my purpose this morning to examine some of the fundamental truths of war and to indicate how these so-called principles of war are ap­plicable to strategy and tactics

Plague Persistence in Western Europe: A Hypothesis

Historical sources documenting recurrent plagues of the “Second Pandemic” usually focus on urban epidemic mortality. Instead, plague persists in remote, rural hinterlands: areas less visible in the written sources of late medieval Europe. Plague spreads as fleas move from relatively resistant rodents, which serve as “maintenance hosts,” to an array of more susceptible rural mammals, now called “amplifying hosts.” Using sources relevant to plague in thinly populated Central and Western Alpine regions, this paper postulates that Alpine Europe could have been a region of plague persistence via its population of wild rodents, particularly the Alpine marmot

Measurement-induced entanglement of two superconducting qubits

We study the problem of two superconducting quantum qubits coupled via a resonator. If only one quanta is present in the system and the number of photons in the resonator is measured with a null result, the qubits end up in an entangled Bell state. Here we look at one source of errors in this quantum nondemolition scheme due to the presence of more than one quanta in the resonator, previous to the measurement. By analyzing the structure of the conditional Hamiltonian with arbitrary number of quanta, we show that the scheme is remarkably robust against these type of errors.Comment: 4 pages, 2 figure