Coherent Imaging Spectroscopy of a Quantum Many-Body Spin System

Quantum simulators, in which well controlled quantum systems are used to reproduce the dynamics of less understood ones, have the potential to explore physics that is inaccessible to modeling with classical computers. However, checking the results of such simulations will also become classically intractable as system sizes increase. In this work, we introduce and implement a coherent imaging spectroscopic technique to validate a quantum simulation, much as magnetic resonance imaging exposes structure in condensed matter. We use this method to determine the energy levels and interaction strengths of a fully-connected quantum many-body system. Additionally, we directly measure the size of the critical energy gap near a quantum phase transition. We expect this general technique to become an important verification tool for quantum simulators once experiments advance beyond proof-of-principle demonstrations and exceed the resources of conventional computers

Quantum information processing with atoms and photons

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62643/1/416238a.pd

Quantum Control of Qubits and Atomic Motion Using Ultrafast Laser Pulses

Pulsed lasers offer significant advantages over CW lasers in the coherent control of qubits. Here we review the theoretical and experimental aspects of controlling the internal and external states of individual trapped atoms with pulse trains. Two distinct regimes of laser intensity are identified. When the pulses are sufficiently weak that the Rabi frequency $\Omega$ is much smaller than the trap frequency \otrap, sideband transitions can be addressed and atom-atom entanglement can be accomplished in much the same way as with CW lasers. By contrast, if the pulses are very strong (\Omega \gg \otrap), impulsive spin-dependent kicks can be combined to create entangling gates which are much faster than a trap period. These fast entangling gates should work outside of the Lamb-Dicke regime and be insensitive to thermal atomic motion.Comment: 16 pages, 15 figure

Inevitability in History

Historians sometimes say that one event or set of events made another event inevitable. This paper proposes an analysis of the concept of inevitability that is employed in such claims. To say that one event E made another event F inevitable is to say that: (1) E and F occurred, and in that temporal order, and (2) After E, and because of E, no action within the power of any living person or persons who desired F not to occur would have been followed by the nonoccurrence of F. One of the corollaries of this analysis is that anyone who asserts an inevitability statement is thereby committed to a true generalization to the effect that conditions like E cause conditions like

Enhancing Both Cooperative Extension and National Environmental Education Resources

State Extension programs can contribute to the successful adoption of national environmental education programs by making locally relevant resources available, creating reference materials to bridge between 4-H project books and other resources, and developing companion materials that supplement national materials with local issues and resources. Such activities provide opportunities to integrate research and teaching with Extension programs and build productive relationships with agencies and organizations. Seven strategies with examples from one state are explained

Improving Cooling Tower Fan System Efficiencies

LecturePg. 159-166.After a look at the problem for air cooled heat exchangers and cooling towers using axial fans, ways to improve system efficiencies in three areas are discussed: before the fin system design is finalized, improvements in the physical equipment as installed, and recognition of performance problems caused by adjacent equipment. Results of a full scale test illustrating fan system efficiency contributions of various components are discussed

Rapid optimization of working parameters of microwave-driven multi-level qubits for minimal gate leakage

We propose an effective method to optimize the working parameters (WPs) of microwave-driven quantum logical gates implemented with multi-level physical qubits. We show that by treating transitions between each pair of levels independently, intrinsic gate errors due primarily to population leakage to undesired states can be estimated accurately from spectroscopic properties of the qubits and minimized by choosing appropriate WPs. The validity and efficiency of the approach are demonstrated by applying it to optimize the WPs of two coupled rf SQUID flux qubits for controlled-NOT (CNOT) operation. The result of this independent transition approximation (ITA) is in good agreement with that of dynamic method (DM). Furthermore, the ratio of the speed of ITA to that of DM scales exponentially as 2^n when the number of qubits n increases.Comment: 4pages, 3 figure