133 research outputs found
Hybrid continuous dynamical decoupling: a photon-phonon doubly dressed spin
We study the parametric interaction between a single Nitrogen-Vacancy
electronic spin and a diamond mechanical resonator in which the spin is
embedded. Coupling between spin and oscillator is achieved by crystal strain,
which is generated upon actuation of the oscillator and which parametrically
modulates the spins' energy splitting. Under coherent microwave driving of the
spin, this parametric drive leads to a locking of the spin Rabi frequency to
the oscillator mode in the megahertz range. Both the Rabi oscillation decay
time and the inhomogeneous spin dephasing time increase by two orders of
magnitude under this spin-locking condition. We present routes to prolong the
dephasing times even further, potentially to the relaxation time limit. The
remarkable coherence protection that our hybrid spin-oscillator system offers
is reminiscent of recently proposed concatenated continuous dynamical
decoupling schemes and results from our robust, drift-free strain-coupling
mechanism and the narrow linewidth of the high-quality diamond mechanical
oscillator employed. Our findings suggest feasible applications in quantum
information processing and sensing.Comment: 6 pages, 4 figure
Resolved sidebands in a strain-coupled hybrid spin-oscillator system
We report on single electronic spins coupled to the motion of mechanical
resonators by a novel mechanism based on crystal strain. Our device consists of
single-crystalline diamond cantilevers with embedded Nitrogen-Vacancy center
spins. Using optically detected electron spin resonance, we determine the
unknown spin-strain coupling constants and demonstrate that our system resides
well within the resolved sideband regime. We realize coupling strengths
exceeding ten MHz under mechanical driving and show that our system has the
potential to reach strong coupling. Our novel hybrid system forms a resource
for future experiments on spin-based cantilever cooling and coherent
spin-oscillator coupling.Comment: 4 pages, 4 figures and supplementary information. Comments welcome.
Further information under http://www.quantum-sensing.physik.unibas.ch
Formes de Whitney et primitives relatives de formes diff\'erentielles sous-analytiques
Let be a real-analytic manifold and a proper
triangulable subanalytic map. Given a subanalytic -form on
whose pull-back to every non singular fiber of is exact, we show tha
has a relative primitive: there is a subanalytic -form
such that . The proof uses a subanalytic
triangulation to translate the problem in terms of "relative Whitney forms"
associated to prisms. Using the combinatorics of Whitney forms, we show that
the result ultimately follows from the subanaliticity of solutions of a special
linear partial differential equation. The work was inspired by a question of
Fran\c{c}ois Treves
Non-reciprocal coherent dynamics of a single spin under closed-contour interaction
Three-level quantum systems have formed a cornerstone of quantum optics since
the discovery of coherent population trapping (CPT) and electromagnetically
induced transparency. Key to these phenomena is quantum interference, which
arises if two of the three available transitions are coherently driven at
well-controlled amplitudes and phases. The additional coherent driving of the
third available transition would form a closed-contour interaction (CCI) from
which fundamentally new phenomena would emerge, including phase-controlled CPT
and one atom interferometry. However, due to the difficulty in experimentally
realising a fully coherent CCI, such aspects of three-level systems remain
unexplored as of now. Here, we exploit recently developed methods for coherent
driving of single Nitrogen-Vacancy (NV) electronic spins to implement highly
coherent CCI driving. Our experiments reveal phase-controlled, single spin
quantum interference fringes, reminiscent of electron dynamics on a triangular
lattice, with the driving field phases playing the role of a synthetic magnetic
flux. We find that for suitable values of this phase, CCI driving leads to
efficient coherence protection of the NV spin, yielding a nearly two orders of
magnitude improvement of the coherence time, even for moderate drive strengths
<~1MHz. Our results establish CCI driving as a novel paradigm in coherent
control of few-level systems that offers attractive perspectives for
applications in quantum sensing or quantum information processing.Comment: 18 pages, 11 figures. Including supplementary material. Comments are
welcome. For further information visit
https://quantum-sensing.physik.unibas.ch/news.htm
Emergence of magnetic structure in supersonic isothermal magnetohydrodynamic turbulence
The inverse transfer of magnetic helicity is a fundamental process which may
explain large scale magnetic structure formation and sustainement. Until very
recently, direct numerical simulations (DNS) of the inverse transfer in
magnetohydrodynamics (MHD) turbulence have been done in incompressible MHD or
at low Mach numbers only. We review first results obtained through DNS of the
isothermal MHD equations at Mach numbers ranging from subsonic to about 10. The
spectral exponent of the magnetic helicity spectrum becomes flatter with
increasing compressibility. When considering the Alfv\'en velocity in place of
the magnetic field however, results found in incompressible MHD, including a
dynamic balance between shear and twist, can be extended to supersonic MHD. In
the global picture of an inverse transfer of magnetic helicity, three phenomena
are at work: a local direct transfer mediated by the large scale velocity
field, a local inverse transfer mediated by the intermediate scale velocity
field and a nonlocal inverse transfer mediated by the small scale velocity
field. The compressive part of the velocity field is geometrically favored in
the local direct transfer and contributes to the nonlocal inverse transfer, but
plays no role in the local inverse transfer.Comment: Chapter in Helicities in Geophysics, Astrophysics and Beyond (AGU
Books, Wiley, 2023 or 2024
Comparative Analysis of Brass Wind Instruments With an Artificial Mouth: First Results
International audienceWe have developed in the past “artificial mouths” to study the behaviour of brass wind instruments (trumpet, trombone) in the playing situation, but without a musician. After using such devices to better understand the physical phenomena involved in brass instruments, we have built and used a new artificial mouth with the objective to test and set up instruments; the artificial mouth is considered here as a “test bench”. In this article, we describe the typical measurements that we have carried out on trumpets, in order to compare them (measurements of oscillation threshold, evolution of the playing frequency according to the dynamic level). As a first result, the artificial mouth allows one to show noticeable differences between instruments. We propose next some research paths which could be explored in order to better control the quality of instruments and, in the future, to introduce the use of an artificial mouth in the design process of brass instruments
- …