2,237 research outputs found
Survival of entanglement in thermal states
We present a general sufficiency condition for the presence of multipartite
entanglement in thermal states stemming from the ground state entanglement. The
condition is written in terms of the ground state entanglement and the
partition function and it gives transition temperatures below which
entanglement is guaranteed to survive. It is flexible and can be easily adapted
to consider entanglement for different splittings, as well as be weakened to
allow easier calculations by approximations. Examples where the condition is
calculated are given. These examples allow us to characterize a minimum gapping
behavior for the survival of entanglement in the thermodynamic limit. Further,
the same technique can be used to find noise thresholds in the generation of
useful resource states for one-way quantum computing.Comment: 6 pages, 2 figures. Changes made in line with publication
recommendations. Motivation and concequences of result clarified, with the
addition of one more example, which applies the result to give noise
thresholds for measurement based quantum computing. New author added with new
result
Identity, community and care in online accounts of hereditary colorectal cancer syndrome
Sociological literature has explored how shifts in the point at which individuals may be designated as diseased impact upon experiences of ill health. Research has shown that experiences of being genetically “at risk” are shaped by and shape familial relations, coping strategies, and new forms of biosociality. Less is known about how living with genetic risk is negotiated in the everyday and over time, and the wider forms of identity, communities and care this involves. This article explores these arrangements drawing on online bloggers’ accounts of Familial Adenomatous Polyposis (FAP). We show how accounts of genetic risk co-exist with more palpable experiences of FAP in everyday life, notably the consequences of prophylactic surgeries. We consider how the act of blogging represents but also constitutes everyday experiences of hereditary cancer syndrome as simultaneously ordinary and exceptional, and reflect on the implications of our analysis for understanding experiences of genetic cancer risk
The uses and functions of ageing celebrity war reporters
This article starts from the premise that recognition of professional authority and celebrity status depends on the embodiment and performance of field-specific dispositional practices: there’s no such thing as a natural, though we often talk about journalistic instinct as something someone simply has or doesn’t have. Next, we have little control over how we are perceived by peers and publics, and what we think are active positioning or subjectifying practices are in fact, after Bourdieu, revelations of already-determined delegation. The upshot is that two journalists can arrive at diametrically opposed judgements on the basis of observation of the same actions of a colleague, and as individuals we are blithely hypocritical in forming (or reciting) evaluations of the professional identity of celebrities. Nowhere is this starker than in the discourse of age-appropriate behaviour, which this paper addresses using the examples of ‘star’ war reporters John Simpson, Kate Adie and Martin Bell. A certain rough-around-the-edges irreverence is central to dispositional authenticity amongst war correspondents, and for ageing hacks this incorporates gendered attitudes to sex and alcohol as well as indifference to protocol. And yet perceived age-inappropriate sexual behaviour is also used to undermine professional integrity, and the paper ends by outlining the phenomenological context that makes possible this effortless switching between amoral and moralising recognition by peers and audiences alike
Production of oriented nitrogen-vacancy color centers in synthetic diamond
The negatively charged nitrogen-vacancy (NV-) center in diamond is an
attractive candidate for applications that range from magnetometry to quantum
information processing. Here we show that only a fraction of the nitrogen
(typically < 0.5 %) incorporated during homoepitaxial diamond growth by
Chemical Vapor Deposition (CVD) is in the form of undecorated NV- centers.
Furthermore, studies on CVD diamond grown on (110) oriented substrates show a
near 100% preferential orientation of NV- centers along only the [111] and
[-1-11] directions, rather than the four possible orientations. The results
indicate that NV centers grow in as units, as the diamond is deposited, rather
than by migration and association of their components. The NV unit of the NVH-
is similarly preferentially oriented, but it is not possible to determine
whether this defect was formed by H capture at a preferentially aligned NV
center or as a complete unit. Reducing the number of NV orientations from 4
orientations to 2 orientations should lead to increased optically-detected
magnetic resonance contrast and thus improved magnetic sensitivity in
ensemble-based magnetometry.Comment: 13 Pages (inlcuding suplementary information), 4 figure
Local distinguishability of quantum states in infinite dimensional systems
We investigate local distinguishability of quantum states by use of the
convex analysis about joint numerical range of operators on a Hilbert space. We
show that any two orthogonal pure states are distinguishable by local
operations and classical communications, even for infinite dimensional systems.
An estimate of the local discrimination probability is also given for some
family of more than two pure states
Transport behavior of holes in boron delta-doped diamond structures
Boron delta-doped diamond structures have been synthesized using microwave plasma chemical vapor deposition and fabricated into FET and gated Hall bar devices for assessment of the electrical characteristics. A detailed study of variable temperature Hall, conductivity, and field-effect mobility measurements was completed. This was supported by Schr€dinger-Poisson and relaxation time o calculations based upon application of Fermi’s golden rule. A two carrier-type model was developed with an activation energy of 1 cm2/Vs and the bulk valence band with high mobility. This new understanding of the transport of holes in such boron delta-doped structures has shown that although Hall mobility as high as 900 cm2/Vs was measured at room temperature, this dramatically overstates the actual useful performance of the device
Undetermined states: how to find them and their applications
We investigate the undetermined sets consisting of two-level, multi-partite
pure quantum states, whose reduced density matrices give absolutely no
information of their original states. Two approached of finding these quantum
states are proposed. One is to establish the relation between codewords of the
stabilizer quantum error correction codes (SQECCs) and the undetermined states.
The other is to study the local complementation rules of the graph states. As
an application, the undetermined states can be exploited in the quantum secret
sharing scheme. The security is guaranteed by their undetermineness.Comment: 6 pages, no figur
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