2,921 research outputs found
Measuring the magnetic moment density in patterned ultrathin ferromagnets with submicron resolution
We present a new approach to infer the surface density of magnetic moments
in ultrathin ferromagnetic films with perpendicular anisotropy. It relies
on quantitative stray field measurements with an atomic-size magnetometer based
on the nitrogen-vacancy center in diamond. The method is applied to
microstructures patterned in a 1-nm-thick film of CoFeB. We report measurements
of with a few percent uncertainty and a spatial resolution in the range
of nm), an improvement by several orders of magnitude over existing
methods. As an example of application, we measure the modifications of
induced by local irradiation with He ions in an ultrathin ferromagnetic
wire. This method offers a new route to study variations of magnetic properties
at the nanoscale.Comment: 9 pages and 7 figures including main text and Supplemental
Informatio
Different methods of evaluation of Monilinia laxa on apricot flowers and branches
- Organic apricot production is currently not profitable.
- The main obstacle to sustainable profitability is brown rot caused by the fungus Monilinia laxa (Aderh. & Ruhl).
- In the current apricot germplasm no source of total resistance has been shown, but some varieties are expressing interesting levels of tolerance.
- A good evaluation of the M. laxa symptoms is essential for a precise diagnosis of the infection and to appreciate differences between tolerant and susceptible varieties and genotypes
Storage and Retrieval of a Microwave Field in a Spin Ensemble
We report the storage and retrieval of a small microwave field from a
superconducting resonator into collective excitations of a spin ensemble. The
spins are nitrogen-vacancy centers in a diamond crystal. The storage time of
the order of 30 ns is limited by inhomogeneous broadening of the spin ensemble.Comment: 4 pages + supplementary material. Submitted to PR
Enhancing single-molecule photostability by optical feedback from quantum-jump detection
We report an optical technique that yields an enhancement of single-molecule
photostability, by greatly suppressing photobleaching pathways which involve
photoexcitation from the triplet state. This is accomplished by dynamically
switching off the excitation laser when a quantum-jump of the molecule to the
triplet state is optically detected. This procedure leads to a lengthened
single-molecule observation time and an increased total number of detected
photons. The resulting improvement in photostability unambiguously confirms the
importance of photoexcitation from the triplet state in photobleaching
dynamics, and may allow the investigation of new phenomena at the
single-molecule level
Strong Coupling of a Spin Ensemble to a Superconducting Resonator
We report the realization of a quantum circuit in which an ensemble of
electronic spins is coupled to a frequency tunable superconducting resonator.
The spins are Nitrogen-Vacancy centers in a diamond crystal. The achievement of
strong coupling is manifested by the appearance of a vacuum Rabi splitting in
the transmission spectrum of the resonator when its frequency is tuned through
the NV center electron spin resonance.Comment: 4 pages, 3 figure
Kerr non-linearity in a superconducting Josephson metamaterial
We present a detailed experimental and theoretical analysis of the dispersion
and non-linear Kerr frequency shifts of plasma modes in a one-dimensional
Josephson junction chain containing 500 SQUIDs in the regime of weak
nonlinearity. The measured low-power dispersion curve agrees perfectly with the
theoretical model if we take into account the Kerr renormalisation of the bare
frequencies and the long-range nature of the island charge screening by a
remote ground plane. We measured the self- and cross-Kerr shifts for the
frequencies of the eight lowest modes in the chain. We compare the measured
Kerr coefficients with theory and find good agreement
Reduced Gutzwiller formula with symmetry: case of a finite group
We consider a classical Hamiltonian on , invariant by a
finite group of symmetry , whose Weyl quantization is a
selfadjoint operator on . If is an irreducible
character of , we investigate the spectrum of its restriction
to the symmetry subspace of
coming from the decomposition of Peter-Weyl. We give
reduced semi-classical asymptotics of a regularised spectral density describing
the spectrum of near a non critical energy . If
is compact, assuming that periodic orbits are
non-degenerate in , we get a reduced Gutzwiller trace formula
which makes periodic orbits of the reduced space appear. The
method is based upon the use of coherent states, whose propagation was given in
the work of M. Combescure and D. Robert.Comment: 20 page
Pseudospectra in non-Hermitian quantum mechanics
We propose giving the mathematical concept of the pseudospectrum a central
role in quantum mechanics with non-Hermitian operators. We relate
pseudospectral properties to quasi-Hermiticity, similarity to self-adjoint
operators, and basis properties of eigenfunctions. The abstract results are
illustrated by unexpected wild properties of operators familiar from
PT-symmetric quantum mechanics.Comment: version accepted for publication in J. Math. Phys.: criterion
excluding basis property (Proposition 6) added, unbounded time-evolution
discussed, new reference
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