Geographic Variation of Health Care Spending on Heart Failure in Metropolitan Areas

The costs of healthcare have long been a concern in the United States. It is well known that these costs vary geographically, but attempts to explain this variation have been met with limited and varied success. This is partly attributable to the fact that data available have restricted analyses to assessing the issue to using Medicare cost per beneficiary. In June, 2013, the Center for Medicare and Medicaid Services (CMS) released new Medicare data that detailed the charges and payments made to hospitals throughout the United States in 2011. In this thesis, this new dataset was used to examine costs of treatment for heart failure, a widespread and serious health concern in the U.S.. Costs were examined from two perspectives: the average Medicare payments and the average amount hospitals charged within metropolitan areas. Ordinary Least Squares (OLS) regression analysis was used in an attempt to explain geographic variation in the Medicare payments for the treatment of heart failure in Metropolitan Statistical Areas (MSAs) based on six key demographic variables identified from previous research on spending per Medicare beneficiary. Additionally, these demographic variables were applied to the average amount hospitals charged for the treatment of heart failure. These six variables include the percent African American, the percent with a Bachelor’s degree or higher, the average number of hospital discharges for heart failure, the percent female, the percent in poverty, and the percent aged sixty-five and older. Results suggest that variables with a key relationship to Medicare payments for the treatment for heart failure include the percent with a Bachelor’s degree or higher and the percent aged sixty-five or older within a MSA. Key variables correlated with the average amount hospitals charged for the treatment of heart failure in a MSA include the average number of hospital discharges for heart failure, the percent female, and the percent aged sixty-five and older within a MSA. Advisor: James Merchan

Microtraps for neutral atoms using superconducting structures in the critical state

Recently demonstrated superconducting atom-chips provide a platform for trapping atoms and coupling them to solid-state quantum systems. Controlling these devices requires a full understanding of the supercurrent distribution in the trapping structures. For type-II superconductors, this distribution is hysteretic in the critical state due to the partial penetration of the magnetic field in the thin superconducting film through pinned vortices. We report here an experimental observation of this memory effect. Our results are in good agreement with the redictions of the Bean model of the critical state without adjustable parameters. The memory effect allows to write and store permanent currents in micron-sized superconducting structures and paves the way towards new types of engineered trapping potentials.Comment: accepted in Phys. Rev.

Coherence-preserving trap architecture for long-term control of giant Rydberg atoms

We present a way to trap a single Rydberg atom, make it long-lived and preserve an internal coherence over time scales reaching into the minute range. We propose to trap using carefully designed electric fields, to inhibit the spontaneous emission in a non resonant conducting structure and to maintain the internal coherence through a tailoring of the atomic energies using an external microwave field. We thoroughly identify and account for many causes of imperfection in order to verify at each step the realism of our proposal.Comment: accepted for publication in PR

Real-time quantum feedback prepares and stabilizes photon number states

Feedback loops are at the heart of most classical control procedures. A controller compares the signal measured by a sensor with the target value. It adjusts then an actuator in order to stabilize the signal towards its target. Generalizing this scheme to stabilize a micro-system's quantum state relies on quantum feedback, which must overcome a fundamental difficulty: the measurements by the sensor have a random back-action on the system. An optimal compromise employs weak measurements providing partial information with minimal perturbation. The controller should include the effect of this perturbation in the computation of the actuator's unitary operation bringing the incrementally perturbed state closer to the target. While some aspects of this scenario have been experimentally demonstrated for the control of quantum or classical micro-system variables, continuous feedback loop operations permanently stabilizing quantum systems around a target state have not yet been realized. We have implemented such a real-time stabilizing quantum feedback scheme. It prepares on demand photon number states (Fock states) of a microwave field in a superconducting cavity and subsequently reverses the effects of decoherence-induced field quantum jumps. The sensor is a beam of atoms crossing the cavity which repeatedly performs weak quantum non-demolition measurements of the photon number. The controller is implemented in a real-time computer commanding the injection, between measurements, of adjusted small classical fields in the cavity. The microwave field is a quantum oscillator usable as a quantum memory or as a quantum bus swapping information between atoms. By demonstrating that active control can generate non-classical states of this oscillator and combat their decoherence, this experiment is a significant step towards the implementation of complex quantum information operations.Comment: 12 pages, 4 figure

The Casimir force for passive mirrors

We show that the Casimir force between mirrors with arbitrary frequency dependent reflectivities obeys bounds due to causality and passivity properties. The force is always smaller than the Casimir force between two perfectly reflecting mirrors. For narrow-band mirrors in particular, the force is found to decrease with the mirrors bandwidth.Comment: 12 pages, 2 figures, LaTe