7,310 research outputs found
On the generalization of linear least mean squares estimation to quantum systems with non-commutative outputs
The purpose of this paper is to study the problem of generalizing the
Belavkin-Kalman filter to the case where the classical measurement signal is
replaced by a fully quantum non-commutative output signal. We formulate a least
mean squares estimation problem that involves a non-commutative system as the
filter processing the non-commutative output signal. We solve this estimation
problem within the framework of non-commutative probability. Also, we find the
necessary and sufficient conditions which make these non-commutative estimators
physically realizable. These conditions are restrictive in practice.Comment: 31 page
Interpolation Approach to Hamiltonian-varying Quantum Systems and the Adiabatic Theorem
Quantum control could be implemented by varying the system Hamiltonian.
According to adiabatic theorem, a slowly changing Hamiltonian can approximately
keep the system at the ground state during the evolution if the initial state
is a ground state. In this paper we consider this process as an interpolation
between the initial and final Hamiltonians. We use the mean value of a single
operator to measure the distance between the final state and the ideal ground
state. This measure could be taken as the error of adiabatic approximation. We
prove under certain conditions, this error can be precisely estimated for an
arbitrarily given interpolating function. This error estimation could be used
as guideline to induce adiabatic evolution. According to our calculation, the
adiabatic approximation error is not proportional to the average speed of the
variation of the system Hamiltonian and the inverse of the energy gaps in many
cases. In particular, we apply this analysis to an example on which the
applicability of the adiabatic theorem is questionable.Comment: 12 pages, to appear in EPJ Quantum Technolog
Dual Actions for Born-Infeld and Dp-Brane Theories
Dual actions with respect to U(1) gauge fields for Born-Infeld and -brane
theories are reexamined. Taking into account an additional condition, i.e. a
corollary to the field equation of the auxiliary metric, one obtains an
alternative dual action that does not involve the infinite power series in the
auxiliary metric given by ref. \cite{s14}, but just picks out the first term
from the series formally. New effective interactions of the theories are
revealed. That is, the new dual action gives rise to an effective interaction
in terms of one interaction term rather than infinite terms of different
(higher) orders of interactions physically. However, the price paid for
eliminating the infinite power series is that the new action is not quadratic
but highly nonlinear in the Hodge dual of a -form field strength. This
non-linearity is inevitable to the requirement the two dual actions are
equivalent.Comment: v1: 11 pages, no figures; v2: explanation of effective interactions
added; v3: concision made; v4: minor modification mad
Anisotropic magnetoresistance in single cubic crystals: A theory and its verification
A theory of anisotropic magnetoresistance (AMR) and planar Hall effect (PHE)
in single cubic crystals and its experimental verifications are presented for
the current in the (001) plane. In contrast to the general belief that AMR and
PHE in single crystals are highly sensitive to many internal and external
effects and have no universal features, the theory predicts universal angular
dependencies of longitudinal and transverse resistivity and various
characteristics when magnetization rotates in the (001) plane, the plane
perpendicular to the current, and the plane containing the current and [001]
direction. The universal angular dependencies are verified by the experiments
on Fe30Co70 single cubic crystal film. The findings provide new avenues for
fundamental research and applications of AMR and PHE, because single crystals
offer advantages over polycrystalline materials for band structure and
crystallographic orientation engineering
Heisenberg Picture Approach to the Stability of Quantum Markov Systems
Quantum Markovian systems, modeled as unitary dilations in the quantum
stochastic calculus of Hudson and Parthasarathy, have become standard in
current quantum technological applications. This paper investigates the
stability theory of such systems. Lyapunov-type conditions in the Heisenberg
picture are derived in order to stabilize the evolution of system operators as
well as the underlying dynamics of the quantum states. In particular, using the
quantum Markov semigroup associated with this quantum stochastic differential
equation, we derive sufficient conditions for the existence and stability of a
unique and faithful invariant quantum state. Furthermore, this paper proves the
quantum invariance principle, which extends the LaSalle invariance principle to
quantum systems in the Heisenberg picture. These results are formulated in
terms of algebraic constraints suitable for engineering quantum systems that
are used in coherent feedback networks
Building Ethics into Artificial Intelligence
As artificial intelligence (AI) systems become increasingly ubiquitous, the
topic of AI governance for ethical decision-making by AI has captured public
imagination. Within the AI research community, this topic remains less familiar
to many researchers. In this paper, we complement existing surveys, which
largely focused on the psychological, social and legal discussions of the
topic, with an analysis of recent advances in technical solutions for AI
governance. By reviewing publications in leading AI conferences including AAAI,
AAMAS, ECAI and IJCAI, we propose a taxonomy which divides the field into four
areas: 1) exploring ethical dilemmas; 2) individual ethical decision
frameworks; 3) collective ethical decision frameworks; and 4) ethics in
human-AI interactions. We highlight the intuitions and key techniques used in
each approach, and discuss promising future research directions towards
successful integration of ethical AI systems into human societies
Correlation analysis of intracellular and secreted cytokines via the generalized integrated mean fluorescence intensity
The immune response in humans is usually assessed using immunogenicity assays to provide biomarkers as correlates of protection (CoP). Flow cytometry is the assay of choice to measure intracellular cytokine staining (ICS) of cell-mediated immune (CMI) biomarkers. For CMI analysis, the integrated mean fluorescence intensity (iMFI) was introduced as a metric to represent the total functional CMI response as a CoP. iMFI is computed by multiplying the relative frequency (percent positive) of cells expressing a particular cytokine with the MFI of that population, and correlates better with protection in challenge models than either the percentage or the MFI of the cytokine-positive population. While determination of the iMFI as a CoP can readily be accomplished in animal models that allow challenge/protection experiments, this is not feasible in humans for ethical reasons. As a first step toward extending the iMFI concept to humans, we investigated the correlation of the iMFI derived from a human innate immune response ICS assay with functional cytokine release into the culture supeRNAtant, as innate cytokines need to be released to have a functional impact. Next, we developed a quantitatively more correlative mathematical approach for calculating the functional response of cytokine-producing cells by incorporating the assignment of different weights to the magnitude (frequency of cytokine-positive cells) and the quality (the MFI) of the observed innate immune response. We refer to this model as generalized iMFI. © 2010 Interantional Society for Advancement of Cytometry
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