3,283 research outputs found
A probabilistic and information theoretic interpretation of quantum evolutions
In quantum mechanics, outcomes of measurements on a state have a
probabilistic interpretation while the evolution of the state is treated
deterministically. Here we show that one can also treat the evolution as being
probabilistic in nature and one can measure `which unitary' happened. Likewise,
one can give an information-theoretic interpretation to evolutions by defining
the entropy of a completely positive map. This entropy gives the rate at which
the informational content of the evolution can be compressed. One cannot
compress this information and still have the evolution act on an unknown state,
but we demonstrate a general scheme to do so probabilistically. This allows one
to generalize super-dense coding to the sending of quantum information. One can
also define the ``interaction-entanglement'' of a unitary, and concentrate this
entanglement.Comment: 9 page
(Quantumness in the context of) Resource Theories
We review the basic idea behind resource theories, where we quantify quantum
resources by specifying a restricted class of operations. This divides the
state space into various sets, including states which are free (because they
can be created under the class of operations), and those which are a resource
(because they cannot be). One can quantify the worth of the resource by the
relative entropy distance to the set of free states, and under certain
conditions, this is a unique measure which quantifies the rate of state to
state transitions. The framework includes entanglement, asymmetry and purity
theory. It also includes thermodynamics, which is a hybrid resource theory
combining purity theory and asymmetry. Another hybrid resource theory which
merges purity theory and entanglement can be used to study quantumness of
correlations and discord, and we present quantumness in this more general
framework of resource theories.Comment: review articl
Learning from measurement
The Built Environment Research Group (BERG) at the School of Architecture and Building at Deakin University is involved in the monitoring of building energy consumption, lighting and acoustic levels, as well as material and thermal performance. Such measurements have taken place in several buildings over the last few years. This has been the result of a deliberate policy of BERG to initiate a process that completes the loop of design, prediction, monitoring, verification, teaching, then back to design again. This paper presents a summary of some projects that have involved building monitoring. We have established a methodology for measuring buildings which will be discussed, as well as the reasoning behind our desire to monitor buildings in general. The paper will present a summary of the results of measurement acquired to date (energy consumption, schedules, operation, etc.) and the lessons that have been learned from this monitoring program.<br /
Can the frequency-dependent specific heat be measured by thermal effusion methods?
It has recently been shown that plane-plate heat effusion methods devised for
wide-frequency specific-heat spectroscopy do not give the isobaric specific
heat, but rather the so-called longitudinal specific heat. Here it is shown
that heat effusion in a spherical symmetric geometry also involves the
longitudinal specific heat.Comment: Paper presented at the Fifth International Workshop on Complex
Systems (Sendai, September, 2007), to appear in AIP Conference Proceeding
Supernarrow spectral peaks near a kinetic phase transition in a driven, nonlinear micromechanical oscillator
We measure the spectral densities of fluctuations of an underdamped nonlinear
micromechanical oscillator. By applying a sufficiently large periodic
excitation, two stable dynamical states are obtained within a particular range
of driving frequency. White noise is injected into the excitation, allowing the
system to overcome the activation barrier and switch between the two states.
While the oscillator predominately resides in one of the two states for most
excitation frequencies, a narrow range of frequencies exist where the
occupations of the two states are approximately equal. At these frequencies,
the oscillator undergoes a kinetic phase transition that resembles the phase
transition of thermal equilibrium systems. We observe a supernarrow peak in the
power spectral densities of fluctuations of the oscillator. This peak is
centered at the excitation frequency and arises as a result of noise-induced
transitions between the two dynamical states.Comment: 4 pages, 4 figure
An internal region of the RpoH heat shock transcription factor is critical for rapid degradation by the FtsH protease
AbstractThe proteolysis of regulatory proteins plays an important role in the control of gene expression. The Escherichia coli heat shock sigma factor RpoH (σ32) is highly unstable. Its instability is determined by interactions with the DnaK chaperone machine, RNA polymerase and the ATP-dependent protease FtsH. Bradyrhizobium japonicum expresses three RpoH proteins of which RpoH1 is highly stable. To determine which regions of E. coli RpoH determine protein lability, we generated a number of truncated versions and hybrid proteins. Truncation of N-terminal amino acids had no, and deletion of C-terminal amino acids only a minor effect on stability of RpoH. A major determinant of RpoH lability was mapped to a region of about 85 amino acids (residues 36–122) roughly comprising the sigma factor region 2. This is the first demonstration of an internal RpoH region being responsible for FtsH-mediated degradation
Classical information deficit and monotonicity on local operations
We investigate classical information deficit: a candidate for measure of
classical correlations emerging from thermodynamical approach initiated in
[Phys. Rev. Lett 89, 180402]. It is defined as a difference between amount of
information that can be concentrated by use of LOCC and the information
contained in subsystems. We show nonintuitive fact, that one way version of
this quantity can increase under local operation, hence it does not possess
property required for a good measure of classical correlations. Recently it was
shown by Igor Devetak, that regularised version of this quantity is monotonic
under LO. In this context, our result implies that regularization plays a role
of "monotoniser".Comment: 6 pages, revte
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