199 research outputs found
Coherence of an optically illuminated single nuclear spin qubit
We investigate the coherence properties of individual nuclear spin quantum
bits in diamond [Dutt et al., Science, 316, 1312 (2007)] when a proximal
electronic spin associated with a nitrogen-vacancy (NV) center is being
interrogated by optical radiation. The resulting nuclear spin dynamics are
governed by time-dependent hyperfine interaction associated with rapid
electronic transitions, which can be described by a spin-fluctuator model. We
show that due to a process analogous to motional averaging in nuclear magnetic
resonance, the nuclear spin coherence can be preserved after a large number of
optical excitation cycles. Our theoretical analysis is in good agreement with
experimental results. It indicates a novel approach that could potentially
isolate the nuclear spin system completely from the electronic environment.Comment: 5 pages, 2 figure
Regulation and competition in the Turkish telecommunications industry: an update
This chapter provides an overview of the state of liberalization, competition and regulation of major segments of the telecommunications industry in Turkey. It shows that the competitive stance of the regulatory authority and the development of actual competition has been uneven across segments. Specifically, the degree of competition has been higher in the mobile segment relative to fixed telephony or broadband. The chapter also discusses the new Electronic Communications Law and argues that although not perfect, it provides a coherent basis on which the regulatory authority can pursue competitive objectives in a more even manner. However, the actual development of competition will depend a lot on how the law and the ensuing secondary legislation are actually implemented
Quantum interference of single photons from remote nitrogen-vacancy centers in diamond
We demonstrate quantum interference between indistinguishable photons emitted
by two nitrogen-vacancy (NV) centers in distinct diamond samples separated by
two meters. Macroscopic solid immersion lenses are used to enhance photon
collection efficiency. Quantum interference is verified by measuring a value of
the second-order cross-correlation function .
In addition, optical transition frequencies of two separated NV centers are
tuned into resonance with each other by applying external electric fields.
Extension of the present approach to generate entanglement of remote
solid-state qubits is discussed.Comment: 5 pages, 3 figure
Coherence and control of quantum registers based on electronic spin in a nuclear spin bath
We consider a protocol for the control of few-qubit registers comprising one
electronic spin embedded in a nuclear spin bath. We show how to isolate a few
proximal nuclear spins from the rest of the environment and use them as
building blocks for a potentially scalable quantum information processor. We
describe how coherent control techniques based on magnetic resonance methods
can be adapted to these electronic-nuclear solid state spin systems, to provide
not only efficient, high fidelity manipulation of the registers, but also
decoupling from the spin bath. As an example, we analyze feasible performances
and practical limitations in a realistic setting associated with
nitrogen-vacancy centers in diamond
Accumulation of nonylphenol in gold fish and suckermouth catfish in the semi static aquarium system
[No abstract available
Quantum Storage of Photonic Entanglement in a Crystal
Entanglement is the fundamental characteristic of quantum physics. Large
experimental efforts are devoted to harness entanglement between various
physical systems. In particular, entanglement between light and material
systems is interesting due to their prospective roles as "flying" and
stationary qubits in future quantum information technologies, such as quantum
repeaters and quantum networks. Here we report the first demonstration of
entanglement between a photon at telecommunication wavelength and a single
collective atomic excitation stored in a crystal. One photon from an
energy-time entangled pair is mapped onto a crystal and then released into a
well-defined spatial mode after a predetermined storage time. The other photon
is at telecommunication wavelength and is sent directly through a 50 m fiber
link to an analyzer. Successful transfer of entanglement to the crystal and
back is proven by a violation of the Clauser-Horne-Shimony-Holt (CHSH)
inequality by almost three standard deviations (S=2.64+/-0.23). These results
represent an important step towards quantum communication technologies based on
solid-state devices. In particular, our resources pave the way for building
efficient multiplexed quantum repeaters for long-distance quantum networks.Comment: 5 pages, 3 figures + supplementary information; fixed typo in ref.
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Quantum entanglement between an optical photon and a solid-state spin qubit
Quantum entanglement is among the most fascinating aspects of quantum theory. Entangled optical photons are now widely used for fundamental tests of quantum mechanics and applications such as quantum cryptography. Several recent experiments demonstrated entanglement of optical photons with trapped ions, atoms and atomic ensembles, which are then used to connect remote long-term memory nodes in distributed quantum networks. Here we realize quantum entanglement between the polarization of a single optical photon and a solid-state qubit associated with the single electronic spin of a nitrogen vacancy centre in diamond. Our experimental entanglement verification uses the quantum eraser technique, and demonstrates that a high degree of control over interactions between a solid-state qubit and the quantum light field can be achieved. The reported entanglement source can be used in studies of fundamental quantum phenomena and provides a key building block for the solid-state realization of quantum optical networks
Properties of nitrogen-vacancy centers in diamond: group theoretic approach
We present a procedure that makes use of group theory to analyze and predict
the main properties of the negatively charged nitrogen-vacancy (NV) center in
diamond. We focus on the relatively low temperatures limit where both the
spin-spin and spin-orbit effects are important to consider. We demonstrate that
group theory may be used to clarify several aspects of the NV structure, such
as ordering of the singlets in the () electronic configuration, the
spin-spin and the spin-orbit interactions in the () electronic
configuration. We also discuss how the optical selection rules and the response
of the center to electric field can be used for spin-photon entanglement
schemes. Our general formalism is applicable to a broad class of local defects
in solids. The present results have important implications for applications in
quantum information science and nanomagnetometry.Comment: 30 pages, 6 figure
Harnessing nuclear spin polarization fluctuations in a semiconductor nanowire
Soon after the first measurements of nuclear magnetic resonance (NMR) in a
condensed matter system, Bloch predicted the presence of statistical
fluctuations proportional to in the polarization of an ensemble of
spins. First observed by Sleator et al., so-called "spin noise" has
recently emerged as a critical ingredient in nanometer-scale magnetic resonance
imaging (nanoMRI). This prominence is a direct result of MRI resolution
improving to better than 100 nm^3, a size-scale in which statistical spin
fluctuations begin to dominate the polarization dynamics. We demonstrate a
technique that creates spin order in nanometer-scale ensembles of nuclear spins
by harnessing these fluctuations to produce polarizations both larger and
narrower than the natural thermal distribution. We focus on ensembles
containing ~10^6 phosphorus and hydrogen spins associated with single InP and
GaP nanowires (NWs) and their hydrogen-containing adsorbate layers. We monitor,
control, and capture fluctuations in the ensemble's spin polarization in
real-time and store them for extended periods. This selective capture of large
polarization fluctuations may provide a route for enhancing the weak magnetic
signals produced by nanometer-scale volumes of nuclear spins. The scheme may
also prove useful for initializing the nuclear hyperfine field of electron spin
qubits in the solid-state.Comment: 18 pages, 5 figure
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