35,217 research outputs found
A wave-function Monte Carlo method for simulating conditional master equations
Wave-function Monte Carlo methods are an important tool for simulating
quantum systems, but the standard method cannot be used to simulate decoherence
in continuously measured systems. Here we present a new Monte Carlo method for
such systems. This was used to perform the simulations of a continuously
measured nano-resonator in [Phys. Rev. Lett. 102, 057208 (2009)].Comment: 4 pages, revtex 4, 1 eps figure. v2: correction to Eqs (3),(9), and
(11); v3 added further informatio
‘The party’s over’: critical junctures, crises and the politics of housing policy
The key argument set out in this article is that historical and comparative forms of investigation are necessary if we are to better understand the ambitions and scope of contemporary housing interventions. To demonstrate the veracity of our claim, we have set out an analysis of the UK housing polices enacted in the mid-1970s as a basis for comparison with those pursued 40 years later. The article begins with a critical summary of some of the methodological approaches adopted by researchers used to interpret housing policy. In the main section, we present our critical analysis of housing policy reforms (implemented by the Labour government between 1974 and 1979) noting both their achievements and limitations. In the concluding section, we use our interpretation of this period as a basis to judge contemporary housing policy and reflect on the methodological issues that arise from our analysis
Quantum communication via a continuously monitored dual spin chain
We analyze a recent protocol for the transmission of quantum states via a
dual spin chain [Burgarth and Bose, Phys. Rev. A 71, 052315 (2005)] under the
constraint that the receiver's measurement strength is finite. That is, we
consider the channel where the ideal, instantaneous and complete von Neumann
measurements are replaced with a more realistic continuous measurement. We show
that for optimal performance the measurement strength must be "tuned" to the
channel spin-spin coupling, and once this is done, one is able to achieve a
similar transmission rate to that obtained with ideal measurements. The spin
chain protocol thus remains effective under measurement constraints.Comment: 5 pages, revtex 4, 3 eps figure
Rapid purification of quantum systems by measuring in a feedback-controlled unbiased basis
Rapid-purification by feedback --- specifically, reducing the mean impurity
faster than by measurement alone --- can be achieved by making the eigenbasis
of the density matrix to be unbiased relative to the measurement basis. Here we
further examine the protocol introduced by Combes and Jacobs [Phys.Rev.Lett.
{\bf 96}, 010504 (2006)] involving continuous measurement of the observable
for a -dimensional system. We rigorously re-derive the lower bound
on the achievable speed-up factor, and also an upper bound, namely
, for all feedback protocols that use measurements in unbiased bases.
Finally we extend our results to independent measurements on a register of
qubits, and derive an upper bound on the achievable speed-up factor that
scales linearly with .Comment: v2: published versio
Rapid Measurement of Quantum Systems using Feedback Control
We introduce a feedback control algorithm that increases the speed at which a
measurement extracts information about a -dimensional system by a factor
that scales as . Generalizing this algorithm, we apply it to a register of
qubits and show an improvement O(n). We derive analytical bounds on the
benefit provided by the feedback and perform simulations that confirm that this
speedup is achieved.Comment: 4 pages, 4 figures. V2: Minor correction
The Changing Face of Medicine: Women Doctors and the Evolution of Health Care in America
[Excerpt] This book is a case study of one profession that plays a key role in the health care sector, which now represents about one seventh of the U.S. economy. It examines the most dramatic demographic change in this sector in the last century. But the issues we raise are likely to be of interest more broadly for what they say about the changing roles of women in contemporary society. Women\u27s entry into medicine is taken as dramatic evidence that the barriers to opportunity for women are rapidly falling in America. Does the experience of female physicians to date bear out this optimistic view? An alternative view is that gender roles remain deeply entrenched in our institutions and culture. Specifically, the gender division of household labor continues to constrain the choices of all women. The trade-offs between work and family may be clearest in the most demanding professions, such as law and medicine, which require a high degree of professional devotion.
Our study builds on the fine histories of women in medicine written by Walsh, Morantz-Sanchez, and More. The analysis presented here focuses on the period since 1970, thus complementing the important studies of Bowman and colleagues and Bickel. Lorber examined the experiences of the generation of women who pioneered the transformation of the profession. With the benefit of additional decades of perspective, we are in a position to examine whether the role of gender in medicine is changing
Global Education in Second Language Teaching
This article paints an optimistic picture of the role we second language teachers can play not only in improving our students' language proficiency but also in infusing global education into our classes as we join with our students to address global concerns, such as peace, prosperity, environmental protection, and human rights. The article is divided into four parts. The first part describes global education and identifies organizations of second language educators participating in global education. The second part of the article focuses on two key areas of global education: peace education and environmental education. Next, we address questions that second language teachers frequently ask about including global education in their teaching. Lastly, we supply lists of print and electronic resources on peace education and environmental education
Synergism of He-3 acquisition with lunar base evolution
Researchers have discovered that the lunar surface contains a valuable fusion fuel element that is relatively scarce on Earth. This element, He-3, originates from the solar wind that has bombarded the surface of the Moon over geologic time. Mining operations to recover this resource would allow the by-product acquisition of hydrogen, water, carbon dioxide, carbon monoxide, methane, and nitrogen from the lunar surface with relatively minimal additional resource investment when compared to the costs to supply these resources from Earth. Two configurations for the He-3 mining system are discussed, and the impacts of these mining operations on a projected lunar base scenario are assessed. We conclude that the acquisition of He-3 is feasible with minimal advances in current state-of-the-art technologies and could support a terrestrial nuclear fusion power economy with the lowest hazard risk of any nuclear reaction known. Also, the availability of the by-products of He-3 acquisition from the Moon could significantly reduce the operational requirements of a lunar base and increase the commercialization potential of the base through consumable resupply of the lunar base itself, other components of the space infrastructure, and other space missions
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