2,328 research outputs found
Generalized L\"uscher's Formula in Multichannel Baryon-Baryon Scattering
In this paper, L\"uscher's formula is generalized to the case of two
spin- particles in two-channel scattering based on Ref.
\cite{Li:2012bi}. This is first done in a non-relativistic quantum mechanics
model and then generalized to quantum field theory. We show that L\"uscher's
formula obtained from these two different methods are equivalent up to terms
that are exponentially suppressed in the box size. This formalism can be
readily applied to future lattice QCD calculations.Comment: Introduction expanded and references added. 10 pages, no figure
Experimentally reducing the quantum measurement back-action in work distributions by a collective measurement
In quantum thermodynamics, the standard approach to estimate work
fluctuations in unitary processes is based on two projective measurements, one
performed at the beginning of the process and one at the end. The first
measurement destroys any initial coherence in the energy basis, thus preventing
later interference effects. In order to decrease this back-action, a scheme
based on collective measurements has been proposed in~[PRL 118, 070601 (2017)].
Here, we report its experimental implementation in an optical system. The
experiment consists of a deterministic collective measurement on identically
prepared two qubits, encoded in the polarisation and path degree of a single
photon. The standard two projective measurement approach is also experimentally
realized for comparison. Our results show the potential of collective schemes
to decrease the back-action of projective measurements, and capture subtle
effects arising from quantum coherence.Comment: 9 pages, 4 figure
A multi-wavelength observation and investigation of six infrared dark clouds
Context. Infrared dark clouds (IRDCs) are ubiquitous in the Milky Way, yet
they play a crucial role in breeding newly-formed stars.
Aims. With the aim of further understanding the dynamics, chemistry, and
evolution of IRDCs, we carried out multi-wavelength observations on a small
sample.
Methods. We performed new observations with the IRAM 30 m and CSO 10.4 m
telescopes, with tracers , HCN, , ,
DCO, SiO, and DCN toward six IRDCs G031.97+00.07, G033.69-00.01,
G034.43+00.24, G035.39-00.33, G038.95-00.47, and G053.11+00.05.
Results. We investigated 44 cores including 37 cores reported in previous
work and seven newly-identified cores. Toward the dense cores, we detected 6
DCO, and 5 DCN lines. Using pixel-by-pixel spectral energy distribution
(SED) fits of the 70 to 500 m, we obtained dust
temperature and column density distributions of the IRDCs. We found that emission has a strong correlation with the dust temperature and column
density distributions, while showed the weakest correlation. It
is suggested that is indeed a good tracer in very dense
conditions, but is an unreliable one, as it has a relatively
low critical density and is vulnerable to freezing-out onto the surface of cold
dust grains. The dynamics within IRDCs are active, with infall, outflow, and
collapse; the spectra are abundant especially in deuterium species.
Conclusions. We observe many blueshifted and redshifted profiles,
respectively, with and toward the same core. This
case can be well explained by model "envelope expansion with core collapse
(EECC)".Comment: 24 pages, 11 figures, 4 tables. To be published in A&A. The
resolutions of the pictures are cut dow
Abortive Apoptosis and Its Profound Effects on Radiation, Chemical, and Oncogene-Induced Carcinogenesis
Traditionally apoptosis and the apoptotic machinery have been deemed as anticarcinogenic because of their presumed roles in eliminating damaged or unwanted cells. However, recent work from our laboratory and others have shown that the established paradigm is deeply flawed. The fundamental flaw is the assumption that apoptosis, once initiated, is irreversible and invariably leads to cell death. However, there is increasing evidence that cells can survive activation of the apoptotic cascade. This new revelation about abortive apoptotic cells can dramatically change our assessment of the biological roles of apoptosis. In this brief review, we will cover some of the original studies that report the "undead" apoptotic cells and how they lead to unexpected new roles for apoptotic factors in space radiation and other stress induced genetic instability and carcinogenesis. We will also review exciting new discoveries on the association among abortive apoptosis, spontaneous DNA double strand breaks, DNA damage response, and stemness of cancer cells
Deterministic realization of collective measurements via photonic quantum walks
Collective measurements on identically prepared quantum systems can extract
more information than local measurements, thereby enhancing
information-processing efficiency. Although this nonclassical phenomenon has
been known for two decades, it has remained a challenging task to demonstrate
the advantage of collective measurements in experiments. Here we introduce a
general recipe for performing deterministic collective measurements on two
identically prepared qubits based on quantum walks. Using photonic quantum
walks, we realize experimentally an optimized collective measurement with
fidelity 0.9946 without post selection. As an application, we achieve the
highest tomographic efficiency in qubit state tomography to date. Our work
offers an effective recipe for beating the precision limit of local
measurements in quantum state tomography and metrology. In addition, our study
opens an avenue for harvesting the power of collective measurements in quantum
information processing and for exploring the intriguing physics behind this
power.Comment: Close to the published versio
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