809 research outputs found
Entanglement Typicality
We provide a summary of both seminal and recent results on typical
entanglement. By typical values of entanglement, we refer here to values of
entanglement quantifiers that (given a reasonable measure on the manifold of
states) appear with arbitrarily high probability for quantum systems of
sufficiently high dimensionality. We work within the Haar measure framework for
discrete quantum variables, where we report on results concerning the average
von Neumann and linear entropies as well as arguments implying the typicality
of such values in the asymptotic limit. We then proceed to discuss the
generation of typical quantum states with random circuitry. Different phases of
entanglement, and the connection between typical entanglement and
thermodynamics are discussed. We also cover approaches to measures on the
non-compact set of Gaussian states of continuous variable quantum systems.Comment: Review paper with two quotes and minimalist figure
Coherent quantum effects through dispersive bosonic media
The coherent evolution of two atomic qubits mediated by a set of bosonic
field modes is investigated. By assuming a specific encoding of the quantum
states in the internal levels of the two atoms we show that entangling quantum
gates can be realised, with high fidelity, even when a large number of
mediating modes is involved. The effect of losses and imperfections on the
gates' operation is also considered in detail.Comment: 7 pages, 10 figure
Teleportation fidelities of squeezed states from thermodynamical state space measures.
Published versio
Five star hotels of a Multinational Enterprise in countries of the transitional periphery: A case study in human resources management
The paper examines the application of human resource management (HRM) practices by a Multinational Enterprise (MNE) whose operations extend from unexplored post-Soviet countries’ transitional periphery economies to advanced economies. By involving hotels of a global luxury US chain in Azerbaijan (Caucasus) and Kyrgyzstan (Central Asia), this in-depth case study focuses on the labour-intensive hospitality industry which, although being relatively neglected by mainstream research, is among the first movers in new markets through the setting of business infrastructure and then leisure tourism. Through Whitley's dimensions of employer–employee interdependence and employee delegation, comparisons highlighted few differences between properties operating in the particular transitional periphery economies and those in a developed country (Germany) owned by the same chain. On the basis of corroboration obtained through a multiple case study methodology, dissimilarities identified were in terms of the flexibility of employment, outsourcing and dismissal procedures; however, despite socio-economic differences across nations, it is argued that luxury hospitality MNEs are able to maintain an overall uniform implementation of HRM policies and practices regardless of locale through a “geocentric” approach as illustrated by Perlmutter (1969) in his seminal work
Probing the diamagnetic term in light–matter interaction
We address the quantum estimation of the diamagnetic, or A 2, term in an effective model of light–matter interaction featuring two coupled oscillators. First, we calculate the quantum Fisher information of the diamagnetic parameter in the interacting ground state. Then, we find that typical measurements on the transverse radiation field, such as homodyne detection or photon counting, permit to estimate the diamagnetic coupling constant with near-optimal efficiency in a wide range of model parameters. Should the model admit a critical point, we also find that both measurements would become asymptotically optimal in its vicinity. Finally, we discuss binary discrimination strategies between the two most debated hypotheses involving the diamagnetic term in circuit QED. While we adopt a terminology appropriate to the Coulomb gauge, our results are also relevant for the electric dipole gauge. In that case, our calculations would describe the estimation of the so-called transverse P 2 term. The derived metrological benchmarks are general and relevant to any implementation of the model, cavity and circuit QED being two relevant examples
Quantifying decoherence in continuous variable systems
We present a detailed report on the decoherence of quantum states of
continuous variable systems under the action of a quantum optical master
equation resulting from the interaction with general Gaussian uncorrelated
environments. The rate of decoherence is quantified by relating it to the decay
rates of various, complementary measures of the quantum nature of a state, such
as the purity, some nonclassicality indicators in phase space and, for two-mode
states, entanglement measures and total correlations between the modes.
Different sets of physically relevant initial configurations are considered,
including one- and two-mode Gaussian states, number states, and coherent
superpositions. Our analysis shows that, generally, the use of initially
squeezed configurations does not help to preserve the coherence of Gaussian
states, whereas it can be effective in protecting coherent superpositions of
both number states and Gaussian wave packets.Comment: Review article; 36 pages, 19 figures; typos corrected, references
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Phase Synchronization in Railway Timetables
Timetable construction belongs to the most important optimization problems in
public transport. Finding optimal or near-optimal timetables under the
subsidiary conditions of minimizing travel times and other criteria is a
targeted contribution to the functioning of public transport. In addition to
efficiency (given, e.g., by minimal average travel times), a significant
feature of a timetable is its robustness against delay propagation. Here we
study the balance of efficiency and robustness in long-distance railway
timetables (in particular the current long-distance railway timetable in
Germany) from the perspective of synchronization, exploiting the fact that a
major part of the trains run nearly periodically. We find that synchronization
is highest at intermediate-sized stations. We argue that this synchronization
perspective opens a new avenue towards an understanding of railway timetables
by representing them as spatio-temporal phase patterns. Robustness and
efficiency can then be viewed as properties of this phase pattern
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