876 research outputs found
Controlling qubit transitions during non-adiabatic rapid passage through quantum interference
In adiabatic rapid passage, the Bloch vector of a qubit is inverted by slowly
inverting an external field to which it is coupled, and along which it is
initially aligned. In non-adiabatic twisted rapid passage, the external field
is allowed to twist around its initial direction with azimuthal angle \phi(t)
at the same time that it is non-adiabatically inverted. For polynomial twist,
\phi(t) \sim Bt^{n}. We show that for n \ge 3, multiple qubit resonances can
occur during a single inversion of the external field, producing strong
interference effects in the qubit transition probability. The character of the
interference is controllable through variation of the twist strength B.
Constructive and destructive interference are possible, greatly enhancing or
suppressing qubit transitions. Experimental confirmation of these controllable
interference effects has already occurred. Application of this interference
mechanism to the construction of fast fault-tolerant quantum CNOT and NOT gates
is discussed.Comment: 8 pages, 7 figures, 2 tables; submitted to J. Mod. Op
A new spin-2 self-dual model in
There are three self-dual models of massive particles of helicity +2 (or -2)
in . Each model is of first, second, and third-order in derivatives.
Here we derive a new self-dual model of fourth-order, \cL {SD}^{(4)}, which
follows from the third-order model (linearized topologically massive gravity)
via Noether embedment of the linearized Weyl symmetry. In fact, each self-dual
model can be obtained from the previous one \cL {SD}^{(i)} \to \cL
{SD}^{(i+1)}, i=1,2,3 by the Noether embedment of an appropriate gauge
symmetry, culminating in \cL {SD}^{(4)}. The new model may be identified with
the linearized version of \cL {HDTMG} = \epsilon^{\mu\nu\rho}
\Gamma_{\mu\gamma}^\epsilon (\p_\nu\Gamma_{\epsilon\rho}^\gamma +
(2/3)\Gamma_{\nu\delta}^\gamma \Gamma_{\rho\epsilon}^\delta) /8 m +
\sqrt{-g}(R_{\mu\nu} R^{\nu\mu} - 3 R^2/8) /2 m^2 . We also construct a master
action relating the third-order self-dual model to \cL {SD}^{(4)} by means of
a mixing term with no particle content which assures spectrum equivalence of
\cL {SD}^{(4)} to other lower-order self-dual models despite its pure higher
derivative nature and the absence of the Einstein-Hilbert action. The relevant
degrees of freedom of \cL {SD}^{(4)} are encoded in a rank-two tensor which
is symmetric, traceless and transverse due to trivial (non-dynamic) identities,
contrary to other spin-2 self-dual models. We also show that the Noether
embedment of the Fierz-Pauli theory leads to the new massive gravity of
Bergshoeff, Hohm and Townsend.Comment: 14 pages, no figures, typos fixed, reference (19) modifie
The Onset of Resonance-Controlled Instability in Spherical Bubble Oscillations
Single bubble dynamics are investigated using acoustic techniques for isolation and manipulation. The goal of the investigations is to understand the dynamic origin of the various phenomena that bubbles exhibit: light emission, enhanced mass transport, chaotic and quasiperiodic oscillations, and translations. Once understood, acoustically manipulated bubbles can serve as platforms for materials effects on free surfaces, using surfactants to alter surface rheology and observing how that affects both dynamics and also mass transport. The effects of gravity on the problem will be shown to be significant. The first set of observations from 1g experimentation are presented. These observations are of the onset conditions for instability of the spherical shape of the bubble. For the size range 55-90 microns in diameter we observe instability governed by resonant mode coupling, which is significantly affected by the buoyant force and its effects
Mie scattering from a sonoluminescing air bubble in water
Applied Optics, Volume 34, No. 15, pp. 2648-2654 (20 May 1995)A single bubble of air in water can emit pulses of blue-white light that have durations of less than 50 ps
while it is oscillating in an acoustic standing wave. The emission is called sonoluminescence. A
knowledge of the bubble diameter throughout the cycle, and in particular near the time of sonoluminescence
emission, can provide important information about the phenomenon. A new Mie scattering
technique is developed to determine the size of the bubble through its expansion and collapse during the
acoustic cycle. The technique does not rely on an independent means of calibration or on accurate
measurements of the scattered intensity.This work was supported in part by the Naval Postgraduate School Research Program and the Office of Naval Research
Type II supernova spectral diversity, II: spectroscopic and photometric correlations
We present an analysis of observed trends and correlations between a large range of spectral and photometric parameters of more than 100 type II supernovae (SNe II), during the photospheric phase. We define a common epoch for all SNe of 50 days post-explosion, where the majority of the sample is likely to be under similar physical conditions. Several correlation matrices are produced to search for interesting trends between more than 30 distinct light-curve and spectral properties that characterize the diversity of SNe II. Overall, SNe with higher expansion velocities are brighter, have more rapidly declining light curves, shorter plateau durations, and higher 56Ni masses. Using a larger sample than previous studies, we argue that "Pd" - the plateau duration from the transition of the initial to "plateau" decline rates to the end of the "plateau" - is a better indicator of the hydrogen envelope mass than the traditionally used optically thick phase duration (OPTd: explosion epoch to end of plateau). This argument is supported by the fact that Pd also correlates with s 3, the light-curve decline rate at late times: lower Pd values correlate with larger s 3 decline rates. Large s 3 decline rates are likely related to lower envelope masses, which enables gamma-ray escape. We also find a significant anticorrelation between Pd and s 2 (the plateau decline rate), confirming the long standing hypothesis that faster declining SNe II (SNe IIL) are the result of explosions with lower hydrogen envelope masses and therefore have shorter Pd values.Fil: Gutiérrez, Claudia P.. Universidad de Chile; Chile. University of Southampton; Reino Unido. European Southern Observatory Santiago; Chile. Millennium Institute Of Astrophysics; ChileFil: Anderson, Joseph P.. European Southern Observatory Santiago; ChileFil: Hamuy, Mario. Millennium Institute Of Astrophysics; Chile. Universidad de Chile; ChileFil: González Gaitan, Santiago. Universidad de Chile; Chile. Universidade de Lisboa; Portugal. Millennium Institute Of Astrophysics; ChileFil: Galbany, Lluis. University of Pittsburgh at Johnstown; Estados Unidos. University of Pittsburgh; Estados UnidosFil: Dessart, Luc. Universidad de Chile; ChileFil: Stritzinger, Maximilian D.. University Aarhus; DinamarcaFil: Phillips, Mark M.. Las Campanas Observatory; ChileFil: Morrell, Nidia. Las Campanas Observatory; ChileFil: Folatelli, Gaston. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentin
The Sound of Sonoluminescence
We consider an air bubble in water under conditions of single bubble
sonoluminescence (SBSL) and evaluate the emitted sound field nonperturbatively
for subsonic gas-liquid interface motion. Sound emission being the dominant
damping mechanism, we also implement the nonperturbative sound damping in the
Rayleigh-Plesset equation for the interface motion. We evaluate numerically the
sound pulse emitted during bubble collapse and compare the nonperturbative and
perturbative results, showing that the usual perturbative description leads to
an overestimate of the maximal surface velocity and maximal sound pressure. The
radius vs. time relation for a full SBSL cycle remains deceptively unaffected.Comment: 25 pages; LaTex and 6 attached ps figure files. Accepted for
publication in Physical Review
Designing Robust Unitary Gates: Application to Concatenated Composite Pulse
We propose a simple formalism to design unitary gates robust against given
systematic errors. This formalism generalizes our previous observation [Y.
Kondo and M. Bando, J. Phys. Soc. Jpn. 80, 054002 (2011)] that vanishing
dynamical phase in some composite gates is essential to suppress amplitude
errors. By employing our formalism, we naturally derive a new composite unitary
gate which can be seen as a concatenation of two known composite unitary
operations. The obtained unitary gate has high fidelity over a wider range of
the error strengths compared to existing composite gates.Comment: 7 pages, 4 figures. Major revision: improved presentation in Sec. 3,
references and appendix adde
From Sensing to Action: Quick and Reliable Access to Information in Cities Vulnerable to Heavy Rain
Cities need to constantly monitor weather to anticipate heavy storm events and reduce the impact of floods. Information describing precipitation and ground conditions at high spatio-temporal resolution is essential for taking timely action and preventing damages. Traditionally, rain gauges and weather radars are used to monitor rain events, but these sources provide low spatial resolutions and are subject to inaccuracy. Therefore, information needs to be complemented with data from other sources: from citizens' phone calls to the authorities, to relevant online media posts, which have the potential of providing timely and valuable information on weather conditions in the city. This information is often scattered through different, static, and not-publicly available databases. This makes it impossible to use it in an aggregate, standard way, and therefore hampers efficiency of emergency response. In this paper, we describe information sources relating to a heavy rain event in Rotterdam on October 12-14, 2013. Rotterdam weather monitoring infrastructure is composed of a number of rain gauges installed at different locations in the city, as well as a weather radar network. This sensing network is currently scarcely integrated and logged data are not easily accessible during an emergency. Therefore, we propose a reliable, efficient, and low-cost ICT infrastructure that takes information from all relevant sources, including sensors as well as social and user contributed information and integrates them into a unique, cloud-based interface. The proposed infrastructure will improve efficiency in emergency responses to extreme weather events and, ultimately, guarantee more safety to the urban population
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