34 research outputs found
Two-way interconversion of millimeter-wave and optical fields in Rydberg gases
We show that cold Rydberg gases enable an efficient six-wave mixing process
where terahertz or microwave fields are coherently converted into optical
fields and vice versa. This process is made possible by the long lifetime of
Rydberg states, the strong coupling of millimeter waves to Rydberg transitions
and by a quantum interference effect related to electromagnetically induced
transparency (EIT). Our frequency conversion scheme applies to a broad spectrum
of millimeter waves due to the abundance of transitions within the Rydberg
manifold, and we discuss two possible implementations based on focussed
terahertz beams and millimeter wave fields confined by a waveguide,
respectively. We analyse a realistic example for the interconversion of
terahertz and optical fields in rubidium atoms and find that the conversion
efficiency can in principle exceed 90\%.Comment: 11 pages, 6 figures and supplementary informatio
Experimental demonstration of quantum effects in the operation of microscopic heat engines
The heat engine, a machine that extracts useful work from thermal sources, is
one of the basic theoretical constructs and fundamental applications of
classical thermodynamics. The classical description of a heat engine does not
include coherence in its microscopic degrees of freedom. By contrast, a quantum
heat engine might possess coherence between its internal states. Although the
Carnot efficiency cannot be surpassed, and coherence can be performance
degrading in certain conditions, it was recently predicted that even when using
only thermal resources, internal coherence can enable a quantum heat engine to
produce more power than any classical heat engine using the same resources.
Such a power boost therefore constitutes a quantum thermodynamic signature. It
has also been shown that the presence of coherence results in the thermodynamic
equivalence of different quantum heat engine types, an effect with no classical
counterpart. Microscopic heat machines have been recently implemented with
trapped ions, and proposals for heat machines using superconducting circuits
and optomechanics have been made. When operated with standard thermal baths,
however, the machines implemented so far have not demonstrated any inherently
quantum feature in their thermodynamic quantities. Here we implement two types
of quantum heat engines by use of an ensemble of nitrogen-vacancy centres in
diamond, and experimentally demonstrate both the coherence power boost and the
equivalence of different heat-engine types. This constitutes the first
observation of quantum thermodynamic signatures in heat machines
Ultrahigh and persistent optical depths of caesium in Kagom\'e-type hollow-core photonic crystal fibres
Alkali-filled hollow-core fibres are a promising medium for investigating
light-matter interactions, especially at the single-photon level, due to the
tight confinement of light and high optical depths achievable by light-induced
atomic desorption. However, until now these large optical depths could only be
generated for seconds at most once per day, severely limiting the practicality
of the technology. Here we report the generation of highest observed transient
( for up to a minute) and highest observed persistent ( for
hours) optical depths of alkali vapours in a light-guiding geometry to date,
using a caesium-filled Kagom\'e-type hollow-core photonic crystal fibre. Our
results pave the way to light-matter interaction experiments in confined
geometries requiring long operation times and large atomic number densities,
such as generation of single-photon-level nonlinearities and development of
single photon quantum memories.Comment: Author Accepted versio
Zarządzanie i handel zagraniczny w małych i średnich przedsiębiorstwach w warunkach integracji europejskiej: materiały z konferencji
Z przedmowy: "Integracja europejska to proces łączenia, scalania się
odrębnych ekonomicznie, społecznie, kulturowo gospodarek
europejskich krajów. Proces integracji prowadzi do istotnych
przekształceń w sferze gospodarki, strategiach organizacji
i funkcjonowania przedsiębiorstw, handlu międzynarodowym,
działalności marketingowej, strukturach organizacyjnych
i mechanizmach ekonomicznych przedsiębiorstw i instytucji
działających w krajach integrujących się. Proces integracji to
w praktyce proces dostosowywania się struktur gospodarczych;
tworzenia związków kooperacyjno-produkcyjnych; powstawania
trwałych więzi ekonomicznych między przedsiębiorstwami
integrujących się krajów a więc proces kształtowania jednolitego
obszaru gospodarczego z odrębnych a często także wzajemnie
konkurencyjnych krajów, gospodarek, regionów, gałęzi, branż.
Proces międzynarodowej integracji gospodarczej to w dużej
mierze proces tworzenia komplementamości przedsiębiorstw
i instytucji, komplementamości międzygałęziowej i wewnątrz
gałęziowej, w produkcji i wymianie jak też kształtowanie
niezbędnej infrastruktury technicznej i ekonomicznej
umożliwiającej tworzenie sytemu trwałych powiązań
gospodarczych między poszczególnymi krajami."(...
Proposal for spin squeezing in rare-earth ion-doped crystals with a four-color scheme
Achieving spin squeezing within solid-state devices is a long standing
research goal, due to the promise of their particularities, for instance their
long coherence times, the possibility of low-temperature experiments or
integration of entanglement-assisted sensors on-chip. In this work, we
investigate an interferometer-free four-color scheme to achieve spin squeezing
of rare-earth ion-doped crystals. The proposal relies on an analytic derivation
that starts from a Tavis-Cummings model for light-matter interaction, providing
microscopic insights onto spin-squeezing generation. We evidence spin squeezing
signature in the light intensity variance. We consider the two particular cases
of europium- and praseodymium-doped yttrium orthosilicates, workhorses of
quantum technology developments. We show that up to 3~dB of spin squeezing can
be obtained with readily accessible experimental resources, including noise due
to photon scattering. Our results for rare-earth ion-doped crystals add to
promising properties of these platforms for manipulating many-body entangled
states and for high-precision measurements
Proposal for spin squeezing in rare-earth ion-doped crystals with a four-color scheme
Achieving spin squeezing within solid-state devices is a long standing research goal, due to the promise of their particularities, for instance their long coherence times, the possibility of low-temperature experiments or integration of entanglement-assisted sensors on-chip. In this work, we investigate an interferometer-free four-color scheme to achieve spin squeezing of rare-earth ion-doped crystals. The proposal relies on an analytic derivation that starts from a Tavis-Cummings model for light-matter interaction, providing microscopic insights onto spin-squeezing generation. We evidence spin squeezing signature in the light intensity variance. We consider the two particular cases of europium- and praseodymium-doped yttrium orthosilicates, workhorses of quantum technology developments. We show that up to 3~dB of spin squeezing can be obtained with readily accessible experimental resources, including noise due to photon scattering. Our results for rare-earth ion-doped crystals add to promising properties of these platforms for manipulating many-body entangled states and for high-precision measurements
Proposal for spin squeezing in rare-earth ion-doped crystals with a four-color scheme
Achieving spin squeezing within solid-state devices is a long standing research goal, due to the promise of their particularities, for instance their long coherence times, the possibility of low-temperature experiments or integration of entanglement-assisted sensors on-chip. In this work, we investigate an interferometer-free four-color scheme to achieve spin squeezing of rare-earth ion-doped crystals. The proposal relies on an analytic derivation that starts from a Tavis-Cummings model for light-matter interaction, providing microscopic insights onto spin-squeezing generation. We evidence spin squeezing signature in the light intensity variance. We consider the two particular cases of europium- and praseodymium-doped yttrium orthosilicates, workhorses of quantum technology developments. We show that up to 3~dB of spin squeezing can be obtained with readily accessible experimental resources, including noise due to photon scattering. Our results for rare-earth ion-doped crystals add to promising properties of these platforms for manipulating many-body entangled states and for high-precision measurements
Copper(II) complexes of (<i>R</i>,<i>S</i>)-alpha-hydroxymethylornithine and its N<sup>delta</sup>-benzoyl derivative
Complex formation between copper(II) and (R,S)-α-hydroxymethylornithine of (R,S)-Nα-benzoyl-α-hydroxymethylornithine was studied in aqueous solution by potentiometric and spectroscopic (electron paramagnetic resonance and electronic absorption) techniques. The results show that the α-hydroxymethyl derivatives of ornithine are coordinated through the alcoholic group to the copper(II) ion in basic solution. Deprotonation and coordination of the α-hydroxymethyl group occurs and yields species with the amino and/or carboxylato groups also bound to the metal ion
Can the alpha-hydroxymethylated amino acid residue influence the peptide binding ability towards copper(II) ions?
Complexing ability of tetrapeptides Phe– (R,S)HmR–Arg–Lys, Phe–(R)HmR–Arg–Lys and Phe–(R,S)HmO–Arg–Lys containing potential multi-donor systems provided by the novel amino acid α-hydroxymethylarginine or by α-hydroxymethylornithine has been investigated by potentiometry and the spectroscopic methods (EPR, UV-VIS and CD). Their complexes with copper(II) ions were compared with those of the parent peptides Phe–Ala–Ala–Lys, Phe–Ser–Ala–Lys, Phe–Arg–Arg–Lys and Phe–Orn–Arg–Lys. The significant enhancement of thermodynamic stability is observed for the 2N and 3N species. The CD and EPR spectra support square-planar geometry in 3N species formed at physiological pH. The distortion of the metal environment is induced through the bend conformation adopted by the peptide molecule. The Lys residue is the critical factor influencing this geometry distortion in the 3N species. However, the presence of a α-hydroxymethyl group affects the stability of the complexes, most likely by stabilizing conformations suitable for metal complexation