6,100 research outputs found
Tau anomalous magnetic moment form factor at Super B/Flavor factories
The proposed high-luminosity B/Flavor factories offer new opportunities for
the improved determination of the fundamental physical parameters of standard
heavy leptons. Compared to the electron or the muon case, the magnetic
properties of the lepton are largely unexplored. We show that the
electromagnetic properties of the , and in particular its magnetic form
factor, may be measured competitively in these facilities, using unpolarized or
polarized electron beams. Various observables of the 's produced on top
of the resonances, such as cross-section and normal polarization for
unpolarized electrons or longitudinal and transverse asymmetries for polarized
beams, can be combined in order to increase the sensitivity on the magnetic
moment form factor. In the case of polarized electrons, we identify a special
combination of transverse and longitudinal polarizations able to
disentangle this anomalous magnetic form factor from both the charge form
factor and the interference with the Z-mediating amplitude. For an integrated
luminosity of one could achieve a sensitivity of
about , which is several orders of magnitude below any other existing
high- or low-energy bound on the magnetic moment. Thus one may obtain a QED
test of this fundamental quantity to a few % precision.Comment: 20 pages, 4 figure
Non-reciprocal few-photon devices based on chiral waveguide-emitter couplings
We demonstrate the possibility of designing efficient, non reciprocal
few-photon devices by exploiting the chiral coupling between two waveguide
modes and a single quantum emitter. We show how this system can induce
non-reciprocal photon transport at the single-photon level and act as an
optical diode. Afterwards, we also show how the same system shows a
transistor-like behaviour for a two-photon input. The efficiency in both cases
is shown to be large for feasible experimental implementations. Our results
illustrate the potential of chiral waveguide-emitter couplings for applications
in quantum circuitry.Comment: Mathematica notebook attached for calculation of detection
probabilitie
A chiral route to spontaneous entanglement generation
We study the generation of spontaneous entanglement between two qubits
chirally coupled to a waveguide. The maximum achievable concurrence is
demonstrated to increase by a factor of as compared to the
non-chiral coupling situation. The proposed entanglement scheme is shown to be
robust against variation of the qubit properties such as detuning and
separation, which are critical in the non-chiral case. This result relaxes the
restrictive requirements of the non-chiral situation, paving the way towards a
realistic implementation. Our results demonstrate the potential of chiral
waveguides for quantum entanglement protocols.Comment: 5 pages + 1 page supplemental, 4 figure
Single-atom control of the optoelectronic response in sub-nanometric cavities
By means of ab-initio time dependent density functional theory calculations
carried out on an prototypical hybrid plasmonic device (two metallic
nanoparticles bridged by a one-atom junction), we demonstrate the strong
interplay between photoinduced excitation of localized surface plasmons and
electron transport through the single atom. Such an interplay is remarkably
sensitive to the atomic orbitals of the junction. Therefore, we show the
possibility of a twofold tuning (plasmonic response and photoinduced current
across the juntion) just by changing a single atom in the device.Comment: 5 pages, 5 figure
Harvesting Excitons Through Plasmonic Strong Coupling
Exciton harvesting is demonstrated in an ensemble of quantum emitters coupled
to localized surface plasmons. When the interaction between emitters and the
dipole mode of a metallic nanosphere reaches the strong coupling regime, the
exciton conductance is greatly increased. The spatial map of the conductance
matches the plasmon field intensity profile, which indicates that transport
properties can be tuned by adequately tailoring the field of the plasmonic
resonance. Under strong coupling, we find that pure dephasing can have
detrimental or beneficial effects on the conductance, depending on the
effective number of participating emitters. Finally, we show that the exciton
transport in the strong coupling regime occurs on an ultrafast timescale given
by the inverse Rabi splitting (fs), orders of magnitude faster than
transport through direct hopping between the emitters.Comment: 5 pages, 3 figure
Non-Markovian effects in waveguide-mediated entanglement
We study the generation and evolution of entanglement between two qubits
coupled through one-dimensional waveguide modes. By using a complete quantum
electrodynamical formalism we go beyond the Markovian approximation. The
diagonalization of the hamiltonian is carried out, and a set of quasi-localized
eigenstates is found. We show that when the qubit-waveguide coupling is
increased, the Markov approximation is not anymore valid, and the generation of
entanglement is worsened.Comment: 13 pages, 7 figure
Entanglement of two qubits mediated by one-dimensional plasmonic waveguides
We investigate qubit-qubit entanglement mediated by plasmons supported by
one-dimensional waveguides. We explore both the situation of spontaneous
formation of entanglement from an unentangled state and the emergence of driven
steady-state entanglement under continuous pumping. In both cases, we show that
large values for the concurrence are attainable for qubit-qubit distances
larger than the operating wavelength by using plasmonic waveguides that are
currently available.Comment: 4 pages, 4 figures. Minor Changes. Journal Reference added.
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