Superradiance and its implementation in cold atoms inside a hollow-core waveguide

In this thesis, I am intending to understand the cooperative effect of an ensemble of quantum emitters, which constitutes the preliminary elements of our current experimental investigations towards realization of an ultra-narrow linewidth superriant laser. In the first part of the thesis, I investigate the basics of the theory of superradiance (SR), which includes the full derivation of the Hamiltonian and the Lindblad equation for an ensemble of two-level atoms in both free-space and a single-mode waveguide. In addition, I construct the simulations for observing the transition from single-atom uncorrelated spontaneous emission to superradiance in various physical settings, as well as a simulation for the understanding of the cooperative effects of an ensemble of two-level atoms inside an optical cavity. Then, in the second part of the thesis, I introduce the experimental progress we have been making to observe SR with an ensemble of laser-cooled Cs atoms inside a hollow-core photonic crystal fiber (HCPCF). In our experiment, the Cs atoms, initially cooled using a magneto-optical trap (MOT), are guided and confined inside a short piece of HCPCF with a magic-wavelength dipole trap. Currently we have successfully implemented a novel detection methods for studying superradiance

Studies In Mesoscopics And Quantum Microscopies

This thesis begins with a foundational section on quantum optics. The single-photon detectors used in the first chapter were obtained through the Advanced Laboratory Physics Association (ALPhA), which brokered reduced cost for educational use, and the aim of the single-photon work presented in Chapter 1 is to develop modules for use in Illinois Wesleyan\u27s instructional labs beyond the first year of university. Along with the American Association of Physics Teachers, ALPhA encourages capstone-level work, such as Chapter 1 of this honors thesis, which is explicitly designed to play the role of passing on, to a next generation of physics majors, materials that can play a central role in their curriculum. Thus, although such work had previously been done at other institutions, the value added by this work has to do with the impact upon the local curriculum, and the utility of the collation o of these materials into one single, easily accessible form. Beyond its first chapter, this thesis extends into my research projects, each of which, in the long term, carries a motivation that connects back to questions raised in the studies described in Chapter 1. While the first chapter describes ways in which we can experimentally study the ``spin\u27\u27 polarization state of a single photon, the second deals extends the discussion of how information may be encoded into the angular momentum of light, and some of its potential long-term consequences, e.g., for experiments involving optical traps that may someday test for the (controversial) hypothesized existence of a boundary between the microscopic (quantum) and macroscopic (classical) domains. Here, too, the work presented builds upon a body of work in the recent research literature. The final chapter deals with the creation of meso-scale systems for use in advanced optical traps studies. Each of these last two chapters points towards opportunities in physics research that are tentative in nature and, as such, constitute research that is very much aspirational. The citations provided, while not exhaustive, point both towards some of the more useful resources discovered during this work, and to some ongoing controversies in the field. At the same time, these chapters also aim to delineate concrete, specific steps that we have taken, which we believe are of immediate interest in their own rights

Demonstration of Ion Trap Principles

Particle trapping is a state-of-the-art technology, which already a powerful tool for scientists working with micro- and nano-components. Much interest now revolves around length scales where quantum mechanical effects become pronounced. Quantum mechanics forms our only framework for understanding many problems in solid-state physics (e.g., magnetism), and is playing an ever more important role in applied chemistry, biochemistry and many other areas. Trapping technologies provide a test bed for systematic exploration of fundamental paradigms, offering enhancements to our understanding of key mechanisms and, perhaps, opportunities for quantum information technology. We have assembled a Newtonian Lab demonstration trap, demonstrating key principles of an ion trap, as a first step toward more advanced particle-trapping technology. This system utilizes a low-frequency alternating voltage to trap charged micro-particles. We have confirmed that trapping has occurred, by scattering visible laser beams off the trapped particles. Our next step is to explore designs for a hybrid combination of high-frequency optical tweezers with the sort of low-frequency electrostatic trap we have demonstrated, with the goal of stabilizing particles trapped in low-pressure atmospheres, where it may be possible to achieve cooling towards the quantum mechanical ground state of at least one degree of freedom

Automated damage diagnosis of concrete jack arch beam using optimized deep stacked autoencoders and multi-sensor fusion

A novel hybrid framework of optimized deep learning models combined with multi-sensor fusion is developed for condition diagnosis of concrete arch beam. The vibration responses of structure are first processed by principal component analysis for dimensionality reduction and noise elimination. Then, the deep network based on stacked autoencoders (SAE) is established at each sensor for initial condition diagnosis, where extracted principal components and corresponding condition categories are inputs and output, respectively. To enhance diagnostic accuracy of proposed deep SAE, an enhanced whale optimization algorithm is proposed to optimize network meta-parameters. Eventually, Dempster-Shafer fusion algorithm is employed to combine initial diagnosis results from each sensor to make a final diagnosis. A miniature structural component of Sydney Harbour Bridge with artificial multiple progressive damages is tested in laboratory. The results demonstrate that the proposed method can detect structural damage accurately, even under the condition of limited sensors and high levels of uncertainties

Quantum Optics and Single Photon Quantum Information Processing

Poster presentation abstract

Observation of a charged charmoniumlike structure in e+e−→(D∗Dˉ∗)±π∓e^+e^- \to (D^{*} \bar{D}^{*})^{\pm} \pi^\mp at s=4.26\sqrt{s}=4.26GeV

We study the process $e^+e^- \to (D^{*} \bar{D}^{*})^{\pm} \pi^\mp$ at a center-of-mass energy of 4.26GeV using a 827pb$^{-1}$ data sample obtained with the BESIII detector at the Beijing Electron Positron Collider. Based on a partial reconstruction technique, the Born cross section is measured to be $(137\pm9\pm15)$pb. We observe a structure near the $(D^{*} \bar{D}^{*})^{\pm}$ threshold in the $\pi^\mp$ recoil mass spectrum, which we denote as the $Z^{\pm}_c(4025)$. The measured mass and width of the structure are $(4026.3\pm2.6\pm3.7)$MeV/c$^2$ and $(24.8\pm5.6\pm7.7)$MeV, respectively. Its production ratio $\frac{\sigma(e^+e^-\to Z^{\pm}_c(4025)\pi^\mp \to (D^{*} \bar{D}^{*})^{\pm} \pi^\mp)}{\sigma(e^+e^-\to (D^{*} \bar{D}^{*})^{\pm} \pi^\mp)}$ is determined to be $0.65\pm0.09\pm0.06$. The first uncertainties are statistical and the second are systematic.Comment: 7 pages, 4 figures, 1 table; version accepted to be published in PR

Search for the Lepton Flavor Violation Process J/ψ→eμJ/\psi \to e\mu at BESIII

We search for the lepton-flavor-violating decay of the $J/\psi$ into an electron and a muon using $(225.3\pm2.8)\times 10^{6}$ $J/\psi$ events collected with the BESIII detector at the BEPCII collider. Four candidate events are found in the signal region, consistent with background expectations. An upper limit on the branching fraction of $\mathcal{B}(J/\psi \to e\mu)< 1.5 \times 10^{-7}$ (90% C.L.) is obtained

Search for Baryonic Decays of \psi(3770) and \psi(4040)

By analyzing data samples of 2.9 fb^{-1} collected at \sqrt s=3.773 GeV, 482 pb^{-1} collected at \sqrt s=4.009 GeV and 67 pb^{-1} collected at \sqrt s=3.542, 3.554, 3.561, 3.600 and 3.650 GeV with the BESIII detector at the BEPCII storage ring, we search for \psi(3770) and \psi(4040) decay to baryonic final states, including \Lambda\bar\Lambda\pi^+\pi^-, \Lambda \bar\Lambda\pi^0, \Lambda\bar\Lambda\eta, \Sigma^+ \bar\Sigma^-, \Sigma^0 \bar\Sigma^0, \Xi^-\bar\Xi^+ and \Xi^0\bar\Xi^0 decays. None are observed, and upper limits are set at the 90% confidence level.Comment: 9 pages, 3 figure