278 research outputs found
Quantum Seismology
We propose a quantum mechanical method of detecting weak vibrational
disturbances inspired by the protocol of entanglement farming. We consider a
setup where pairs of atoms in their ground state are successively sent through
an optical cavity. It is known that in this way it is possible to drive that
cavity toward a stable fixed-point state. Here we study how that fixed-point
state depends on the time interval between pairs of atoms and on the distance
between the cavity's mirrors. Taking advantage of an extremely precise
resonance effect, we find that there are special values of these parameters
where the fixed-point state is highly sensitive to perturbations, even harmonic
vibrations with frequencies several orders of magnitude below the cavity's
natural frequency. We propose that this sensitivity may be useful for high
precision metrology.Comment: 10 pages, 5 figures. RevTeX 4.
Single trapped ion as a time-dependent harmonic oscillator
We show how a single trapped ion may be used to test a variety of important physical models realized as time-dependent harmonic oscillators. The ion itself functions as its own motional detector through laser-induced electronic transitions. Alsing et al., [Phys. Rev. Lett. 94, 220401 (2005)] proposed that an exponentially decaying trap frequency could be used to simulate (thermal) Gibbons-Hawking radiation in an expanding universe, but the Hamiltonian used was incorrect. We apply our general solution to this experimental proposal, correcting the result for a single ion and showing that while the actual spectrum is different from the Gibbons-Hawking case, it nevertheless shares an important experimental signature with this result
Quantum lattice models that preserve continuous translation symmetry
Bandlimited approaches to quantum field theory offer the tantalizing
possibility of working with fields that are simultaneously both continuous and
discrete via the Shannon Sampling Theorem from signal processing. Conflicting
assumptions in general relativity and quantum field theory motivate the use of
such an appealing analytical tool that could thread the needle to meet both
requirements. Bandlimited continuous quantum fields are isomorphic to lattice
theories, yet without requiring a fixed lattice. Any lattice with a required
minimum spacing can be used. This is an isomorphism that avoids taking the
limit of the lattice spacing going to zero. In this work, we explore the
consequences of this isomorphism, including the emergence of effectively
continuous symmetries in quantum lattice theories. One obtains conserved
lattice observables for these continuous symmetries, as well as a duality of
locality from the two perspectives. We expect this work and its extensions to
provide useful tools for considering numerical lattice models of continuous
quantum fields arising from the availability of discreteness without a fixed
lattice, as well as offering new insights into emergent continuous symmetries
in lattice models and possible laboratory demonstrations of these phenomena.Comment: 16 pages, 5 figure
Cosmological quantum entanglement
We review recent literature on the connection between quantum entanglement
and cosmology, with an emphasis on the context of expanding universes. We
discuss recent theoretical results reporting on the production of entanglement
in quantum fields due to the expansion of the underlying spacetime. We explore
how these results are affected by the statistics of the field (bosonic or
fermionic), the type of expansion (de Sitter or asymptotically stationary), and
the coupling to spacetime curvature (conformal or minimal). We then consider
the extraction of entanglement from a quantum field by coupling to local
detectors and how this procedure can be used to distinguish curvature from
heating by their entanglement signature. We review the role played by quantum
fluctuations in the early universe in nucleating the formation of galaxies and
other cosmic structures through their conversion into classical density
anisotropies during and after inflation. We report on current literature
attempting to account for this transition in a rigorous way and discuss the
importance of entanglement and decoherence in this process. We conclude with
some prospects for further theoretical and experimental research in this area.
These include extensions of current theoretical efforts, possible future
observational pursuits, and experimental analogues that emulate these cosmic
effects in a laboratory setting.Comment: 23 pages, 2 figures. v2 Added journal reference and minor changes to
match the published versio
Quantum coherent control of highly multipartite continuous-variable entangled states by tailoring parametric interactions
The generation of continuous-variable multipartite entangled states is
important for several protocols of quantum information processing and
communication, such as one-way quantum computation or controlled dense coding.
In this article we theoretically show that multimode optical parametric
oscillators can produce a great variety of such states by an appropriate
control of the parametric interaction, what we accomplish by tailoring either
the spatio-temporal shape of the pump, or the geometry of the nonlinear medium.
Specific examples involving currently available optical parametric oscillators
are given, hence showing that our ideas are within reach of present technology.Comment: 14 pages, 5 figure
Within-plant variation in rosmarinus officinalis l. Terpenes and phenols and their antimicrobial activity against the rosemary phytopathogens alternaria alternata and pseudomonas viridiflava
This study investigated within-plant variability of the main bioactive compounds in rosemary (Rosmarinus officinalis L.). Volatile terpenes, including the enantiomeric distribution of monoterpenes, and phenols were analyzed in young and mature foliar, cortical and xylem tissues. In addition, antimicrobial activity of rosmarinic acid and selected terpenes was evaluated against two rosemary pathogens, Alternaria alternata and Pseudomonas viridiflava. Data showed that total concentration and relative contents of terpenes changed in relation to tissue source and age. Their highest total concentration was observed in the young leaves, followed by mature leaves, cortical and xylem tissues. Rosmarinic acid and carnosic acid contents did not show significant differences between leaf tissues of different ages, while young and mature samples showed variations in the content of four flavonoids. These results are useful for a more targeted harvesting of rosemary plants, in order to produce high-quality essential oils and phenolic extracts. Microbial tests showed that several terpenes and rosmarinic acid significantly inhibited the growth of typical rosemary pathogens. Overall, results on antimicrobial activity suggest the potential application of these natural compounds as biochemical markers in breeding programs aimed to select new chemotypes less susceptible to pathogen attacks, and as eco-friendly chemical alternatives to synthetic pesticides
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