162,424 research outputs found
[Report to Chief J. E. Curry, by an unknown author #1]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
[Report to Chief J. E. Curry, by an unknown author #2]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
Optomechanical coupling between ultracold atoms and a membrane oscillator
No full textIn this thesis, I report on the realization of a hybrid optomechanical system in which ultracold atoms are coupled to a micromechanical membrane. The atoms are trapped in the intensity maxima of an optical standing wave formed by retroreflection of a laser beam from the membrane surface. Vibrations of the membrane displace the standing wave, thus coupling to the center-of-mass motion of the atomic ensemble. Conversely, atoms imprint their motion onto the laser light, thereby modulating the radiation pressure force on the membrane. In this way, the laser light mediates a long-distance, coherent coupling between the two systems.
When the trap frequency of the atoms is matched to the membrane frequency, we observe resonant energy transfer. In addition, by applying simultaneous laser cooling to the atoms, we can dissipate energy from the coupled system leading to sympathetic cooling of the membrane mode. The experimental data follows the theoretical estimations that predict the coupling to scale with the number of trapped atoms. Furthermore, by including the finite temperature of the atoms and their spatially inhomogeneous trapping potential in the theoretical model of the optomechanical coupling, we can accurately describe the width and shape of the resonance.
In an improved experimental setup, the membrane is enclosed in a cavity while the atoms are trapped in the standing wave lattice outside the cavity. The presence of the cavity results in a considerable enhancement of the coupling strength in proportion to the cavity finesse. So far we have observed sympathetic cooling of the membrane mode by a factor of 32 starting from room temperature. Theoretical estimates show that in such a setup ground-state cooling of the membrane mode should be possible, allowing one to access the quantum coherent coupling regime
Sympathetic cooling and self-oscillations in a hybrid atom-membrane system
No full textHybrid systems combining mechanical oscillators and ultracold atoms provide novel
opportunities for cooling, detection and quantum control of mechanical motion with
applications in precision sensing, quantum-level signal transduction and for fundamental
tests of quantum mechanics.
In this thesis I present experiments performed with a hybrid atom-membrane
system, in which the vibrations of a Si_3N_4 membrane in an optical cavity are coupled
to the motion of laser-cooled atoms in an optical lattice. The interactions are
mediated by the lattice light over a macroscopic distance and enhanced by the cavity.
Via the coupling to the cold atoms, the fundamental vibrational mode of the
membrane at 2π x 276 kHz is cooled sympathetically from room temperature to
0.4(2) K, even though the mass of the mechanical oscillator exceeds that of the
atomic ensemble by a factor of 4 x 10^10. In other systems, sympathetic cooling
of molecules with cold atoms or ions has been limited to mass ratios of up to 90.
Previous theoretical work has shown that our coupling mechanism is able to cool the
membrane vibration into the ground state and to perform coherent state transfers
between atomic and membrane motion.
Under certain experimental conditions, the atom-membrane system shows self-oscillations,
which arise from an effective delay in the backaction of the atoms onto
the light. This retardation drives the system into limit-cycle oscillations if the coupling
is large. I study the dependence of this instability on several system parameters
and find that a larger atom number and a smaller atom-light detuning make the system
less stable. Further, the stability of the coupled system in presence of a delay is
investigated theoretically and a modified expression for the sympathetic cooling rate
is derived. This model allows to fit the measured atom number dependence with a
delay of τ = 88(1) ns. Moreover, direct measurements of the atomic backaction onto
the lattice light are presented. These show phase lags exceeding 180° in parameter
regimes where the instability is observed, proving that the retardation arises within
the atomic ensemble. Finally, I present the results of numerical simulations, which
show that collective atomic effects within the atomic ensemble in an asymmetric
lattice are able to induce the observed phase lag in the atomic backaction
Murder on the mountain: author talk with Peter J. Wosh
No full textAuthor talk by Peter J. Wosh on May 5th, 2022, on his book, "Murder on the Mountain: crime, passion, and punishment in gilded age New Jersey.
Sympathetic cooling of a membrane oscillator in a hybrid mechanical-atomic system
No full textThe quantum behaviour of macroscopic mechanical oscillators is currently being investigated using a variety of mechanical systems and techniques such as optomechanical cooling and cold damping. As mechanical systems are also very versatile transducers between different physical systems, it is possible to build hybrid systems that combine the advantages of their constituents. This opens up new possibilities for fundamental studies of quantum physics, precision sensing and quantum information processing. Ultra-cold atoms represent one of the best-controlled systems available, thus making a well-developed toolbox for quantum manipulation available to mechanical oscillators in a hybrid system.
In this thesis, I report on the realization of a hybrid mechanical-atomic system consisting of a Si3N4 membrane inside an optical cavity coupled to an ensemble of atoms. The coupling is mediated by a light field that couples the atomic motion to the membrane motion over a large distance. By laser cooling the atomic motion, the membrane is sympathetically cooled via its interaction with the atoms to a temperature of 0.7 K starting from room temperature, despite the enormous mass ratio of 10^10 between the membrane and the atomic ensemble. Up to now, sympathetic cooling had only been used to cool microscopic particles with much lower masses. The system reported in this thesis is the first hybrid system where the back-action of the atoms onto the mechanical oscillator is sufficiently large for practical applications. It represents a significant improvement over a previous experiment in our laboratory, where the atom’s influence onto the mechanical oscillator was barely detectable. An atom-membrane cooperativity C > 1 is achieved, thus enabling the study of effects such as a mechanical analog of electromagnetically induced transparency in the system, which will be investigated in the future. The quantitative analysis of the coupling mechanism also allows to predict experimental requirements for future ground state cooling of the mechanical oscillator, which are within reach. Interestingly, hybrid systems such as ours can provide ground-state cooling of low-frequency mechanical oscillators in a regime, where neither cavity optomechanical cooling nor cold damping can reach the ground state
Mr. Melvin J. Collier, RWWL AUC, June 2011
No full textThis video is a conversation with Mr. Melvin J. Collier. Mr. Collier talks about his book, "From Mississippi to Africa: A Journey of Discovery". Daniel Le, AUC Woodruff Library, is the interviewer
A Tripartite Post-Recession Rebalancing
No full textIn this latest Advance & Rutgers Report, entitled “A Tripartite Post-Recession Rebalancing,” Dean James W. Hughes and Professor Joseph J. Seneca deliver an incisive assessment of the current market conditions and obstacles in the path of our economic recovery. They offer a statistical cautionary tale that the private and public sector need to hear and acknowledge in order for the economy to make continued progress.This report was published as Issue Paper Number 7, November 2011, in Advance & Rutgers Report
Evidence for the decay B0→J/ψω and measurement of the relative branching fractions of meson decays to J/ψη and J/ψη′
No full textFirst evidence of the B 0 → J / ψ ω decay is found and the B s 0 → J / ψ η and B s 0 → J / ψ η ′ decays are studied using a dataset corresponding to an integrated luminosity of 1.0 fb -1 collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV. The branching fractions of these decays are measured relative to that of the B 0 → J / ψ ρ 0 decay:frac(B (B 0 → J / ψ ω), B (B 0 → J / ψ ρ 0)) = 0.89 ± 0.19 (stat) - 0.13 + 0.07 (syst),frac(B (B s 0 → J / ψ η), B (B 0 → J / ψ ρ 0)) = 14.0 ± 1.2 (stat) - 1.5 + 1.1 (syst) - 1.0 + 1.1 (frac(f d, f s)),frac(B (B s 0 → J / ψ η ′), B (B 0 → J / ψ ρ 0)) = 12.7 ± 1.1 (stat) - 1.3 + 0.5 (syst) - 0.9 + 1.0 (frac(f d, f s)), where the last uncertainty is due to the knowledge of f d / f s, the ratio of b-quark hadronization factors that accounts for the different production rate of B 0 and B s 0 mesons. The ratio of the branching fractions of B s 0 → J / ψ η ′ and B s 0 → J / ψ η decays is measured to befrac(B (B s 0 → J / ψ η ′), B (B s 0 → J / ψ η)) = 0.90 ± 0.09 (stat) - 0.02 + 0.06 (syst)
The vanishing author in computer-generated works: a critical analysis of recent Australian case law
No full textAbstract
The use of software is ubiquitous in the creation of many copyright works, yet the requirement in copyright law that every work have a human author who engages in independent intellectual effort means that its use may prevent copyright subsistence. Several recent Australian cases have refocused attention on authorship as an essential criterion of copyright subsistence, and these cases suggest that much computer-produced output may be authorless and thus lack copyright protection. This article, the first in a two-part series, analyses how each case deals with the question of authorship of computer-produced works and why the use of software diminishes copyright protection for a significant number of computer-generated works. The article critiques the application of conventional notions of human authorship developed in the pre-computer age to modern productions and suggests alternative approaches to authorship that satisfy both the major objectives of copyright policy and the need to adapt to the computer age. The article argues that, without a broader judicial approach to authorship of computer-generated works, Parliament must remedy the lacuna in protection for these ‘authorless’ works. Possible solutions for reform are suggested. In a forthcoming article, the author comprehensively examines those reform proposals
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