3,228 research outputs found
Spin-Orbit Qubits of Rare-Earth-Metal Ions in Axially Symmetric Crystal Fields
Contrary to the well known spin qubits, rare-earth qubits are characterized
by a strong influence of crystal field due to large spin-orbit coupling. At low
temperature and in the presence of resonance microwaves, it is the magnetic
moment of the crystal-field ground-state which nutates (for several s) and
the Rabi frequency is anisotropic. Here, we present a study of the
variations of with the magnitude and direction of the
static magnetic field for the odd Er isotope in a single
crystal CaWO:Er. The hyperfine interactions split the
curve into eight different curves which are fitted
numerically and described analytically. These "spin-orbit qubits" should allow
detailed studies of decoherence mechanisms which become relevant at high
temperature and open new ways for qubit addressing using properly oriented
magnetic fields
A Step-by-step Guide to the Realisation of Advanced Optical Tweezers
Since the pioneering work of Arthur Ashkin, optical tweezers have become an
indispensable tool for contactless manipulation of micro- and nanoparticles.
Nowadays optical tweezers are employed in a myriad of applications
demonstrating the importance of these tools. While the basic principle of
optical tweezers is the use of a strongly focused laser beam to trap and
manipulate particles, ever more complex experimental set-ups are required in
order to perform novel and challenging experiments. With this article, we
provide a detailed step- by-step guide for the construction of advanced optical
manipulation systems. First, we explain how to build a single-beam optical
tweezers on a home-made microscope and how to calibrate it. Improving on this
design, we realize a holographic optical tweezers, which can manipulate
independently multiple particles and generate more sophisticated wavefronts
such as Laguerre-Gaussian beams. Finally, we explain how to implement a speckle
optical tweezers, which permit one to employ random speckle light fields for
deterministic optical manipulation.Comment: 29 pages, 7 figure
Global Phase Diagram of the High Tc Cuprates
The high Tc cuprates have a complex phase diagram with many competing phases.
We propose a bosonic effective quantum Hamiltonian based on the projected SO(5)
model with extended interactions, which can be derived from the microscopic
models of the cuprates. The global phase diagram of this model is obtained
using mean-field theory and the Quantum Monte Carlo simulation, which is
possible because of the absence of the minus sign problem. We show that this
single quantum model can account for most salient features observed in the high
Tc cuprates, with different families of the cuprates attributed to different
traces in the global phase diagram. Experimental consequences are discussed and
new theoretical predictions are presented.Comment: 19 pages, 20 figures, with updated references, final versio
The CRISPR-Cas immune system and genetic transfers : reaching an equilibrium
Horizontal gene transfer drives the evolution of
bacterial genomes, including the adaptation to changing
environmental conditions. Exogenous DNA can enter a bacterial
cell through transformation (free DNA or plasmids) or through
the transfer of mobile genetic elements by conjugation
(plasmids) and transduction (bacteriophages). Favorable genes
can be acquired, but undesirable traits can also be inadvertently
acquired through these processes. Bacteria have systems,
such as clustered regularly interspaced short palindromic
repeat CRISPR–associated genes (CRISPR-Cas), that can cleave
foreign nucleic acid molecules. In this review, we discuss recent
advances in understanding CRISPR-Cas system activity against
mobile genetic element transfer through transformation and
conjugation. We also highlight how CRISPR-Cas systems
influence bacterial evolution and how CRISPR-Cas
components affect plasmid replication
Local thermal resonance control of GaInP photonic crystal membrane cavities using ambient gas cooling
We perform spatially dependent tuning of a GaInP photonic crystal cavity
using a continuous wave violet laser. Local tuning is obtained by laser heating
of the photonic crystal membrane. The cavity resonance shift is measured for
different pump positions and for two ambient gases: helium and nitrogen. We
find that the width of the temperature profile induced in the membrane depends
strongly on the thermal conductivity of the ambient gas. For He gas a narrow
spatial width of the temperature profile of 2.8 um is predicted and verified in
experiment.Comment: 4 pages, 5 figure
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