794 research outputs found
Mapping out the quasicondensate transition through the dimensional crossover from one to three dimensions
By measuring the density fluctuations in a highly elongated weakly interacting Bose gas, we observe and quantify the transition from the ideal gas to a quasicondensate regime throughout the dimensional crossover from a purely one-dimensional (1D) to an almost three-dimensional (3D) gas. We show that that the entire transition region and the dimensional crossover are described surprisingly well by the modified Yang-Yang model. Furthermore, we find that at low temperatures the linear density at the quasicondensate transition scales according to an interaction-driven scenario of a longitudinally uniform 1D Bose gas, whereas at high temperatures it scales according to the degeneracy-driven critical scenario of transverse condensation of a 3D ideal gas
Engineering spin-orbit coupling for photons and polaritons in microstructures
One of the most fundamental properties of electromagnetism and special
relativity is the coupling between the spin of an electron and its orbital
motion. This is at the origin of the fine structure in atoms, the spin Hall
effect in semiconductors, and underlies many intriguing properties of
topological insulators, in particular their chiral edge states. Configurations
where neutral particles experience an effective spin-orbit coupling have been
recently proposed and realized using ultracold atoms and photons. Here we use
coupled micropillars etched out of a semiconductor microcavity to engineer a
spin-orbit Hamiltonian for photons and polaritons in a microstructure. The
coupling between the spin and orbital momentum arises from the polarisation
dependent confinement and tunnelling of photons between micropillars arranged
in the form of a hexagonal photonic molecule. Dramatic consequences of the
spin-orbit coupling are experimentally observed in these structures in the
wavefunction of polariton condensates, whose helical shape is directly visible
in the spatially resolved polarisation patterns of the emitted light. The
strong optical nonlinearity of polariton systems suggests exciting perspectives
for using quantum fluids of polaritons11 for quantum simulation of the
interplay between interactions and spin-orbit coupling.Comment: main text: pages 1-11 (4 figures); supplementary material: pages
12-28 (9 figures
Mapping out the quasicondensate transition through the dimensional crossover from one to three dimensions Phys.
By measuring the density fluctuations in a highly elongated weakly interacting Bose gas, we observe and quantify the transition from the ideal gas to a quasicondensate regime throughout the dimensional crossover from a purely one-dimensional (1D) to an almost three-dimensional (3D) gas. We show that that the entire transition region and the dimensional crossover are described surprisingly well by the modified Yang-Yang model. Furthermore, we find that at low temperatures the linear density at the quasicondensate transition scales according to an interaction-driven scenario of a longitudinally uniform 1D Bose gas, whereas at high temperatures it scales according to the degeneracy-driven critical scenario of transverse condensation of a 3D ideal gas. Low-dimensional (one-or two-dimensional) systems can have physical properties dramatically different from their three-dimensional (3D) counterparts. Experimental realizations of such systems in recent years has been particularly exciting in the field of ultracold atomic gases In this paper we address this question for a weakly interacting Bose gas that is confined transversely by a harmonic trap of frequency ω ⊥ /2π but is homogeneous in the thermodynamic limit with respect to the longitudinal direction. The one-dimensional (1D) regime is obtained when the thermal energy k B T and the chemical potential µ become much smaller than the transverse excitation energyhω ⊥ . In the absence of interatomic interactions, the homogeneous 1D gas is characterized by the absence of Bose-Einstein condensation. In the 3D limit, however, for k B T hω ⊥ , a sharp transverse condensation is expected: The atoms accumulate in the transverse ground state due to the saturation of population in the transversally excited states, yet the resulting 1D gas is still uncondensed with respect to the longitudinal states Our study relies on the measurement of atomic density fluctuations, previously used to identify the two limiting regimes-the ideal gas and the quasicondensat
High-finesse Fabry-Perot cavities with bidimensional SiN photonic-crystal slabs
Light scattering by a two-dimensional photonic crystal slab (PCS) can result in dramatic interference effects associated with Fano resonances. Such devices offer appealing alternatives to distributed Bragg reflectors or filters for various applications such as optical wavelength and polarization filters, reflectors, semiconductor lasers, photodetectors, bio-sensors, or non-linear optical components. Suspended PCSs also find natural applications in the field of optomechanics, where the mechanical modes of a suspended slab interact via radiation pressure with the optical field of a high finesse cavity. The reflectivity and transmission properties of a defect-free suspended PCS around normal incidence can be used to couple out-of-plane mechanical modes to an optical field by integrating it in a free space cavity. Here, we demonstrate the successful implementation of a PCS reflector on a high-tensile stress SiN nanomembrane. We illustrate the physical process underlying the high reflectivity by measuring the photonic crystal band diagram. Moreover, we introduce a clear theoretical description of the membrane scattering properties in the presence of optical losses. By embedding the PCS inside a high-finesse cavity, we fully characterize its optical properties. The spectrally, angular, and polarization resolved measurements demonstrate the wide tunability of the membrane's reflectivity, from nearly 0 to 99.9470~ 0.0025 \%, and show that material absorption is not the main source of optical loss. Moreover, the cavity storage time demonstrated in this work exceeds the mechanical period of low-order mechanical drum modes. This so-called resolved sideband condition is a prerequisite to achieve quantum control of the mechanical resonator with light
On the Interface Formation Model for Dynamic Triple Lines
This paper revisits the theory of Y. Shikhmurzaev on forming interfaces as a
continuum thermodynamical model for dynamic triple lines. We start with the
derivation of the balances for mass, momentum, energy and entropy in a
three-phase fluid system with full interfacial physics, including a brief
review of the relevant transport theorems on interfaces and triple lines.
Employing the entropy principle in the form given in [Bothe & Dreyer, Acta
Mechanica, doi:10.1007/s00707-014-1275-1] but extended to this more general
case, we arrive at the entropy production and perform a linear closure, except
for a nonlinear closure for the sorption processes. Specialized to the
isothermal case, we obtain a thermodynamically consistent mathematical model
for dynamic triple lines and show that the total available energy is a strict
Lyapunov function for this system
High-sensitivity AC-charge detection with a MHz-frequency fluxonium qubit
Owing to their strong dipole moment and long coherence times, superconducting
qubits have demonstrated remarkable success in hybrid quantum circuits.
However, most qubit architectures are limited to the GHz frequency range,
severely constraining the class of systems they can interact with. The
fluxonium qubit, on the other hand, can be biased to very low frequency while
being manipulated and read out with standard microwave techniques. Here, we
design and operate a heavy fluxonium with an unprecedentedly low transition
frequency of . We demonstrate resolved sideband cooling of
the ``hot'' qubit transition with a final ground state population of ,
corresponding to an effective temperature of . We further
demonstrate coherent manipulation with coherence times ,
, and single-shot readout of the qubit state.
Importantly, by directly addressing the qubit transition with a capacitively
coupled waveguide, we showcase its high sensitivity to a radio-frequency field.
Through cyclic qubit preparation and interrogation, we transform this
low-frequency fluxonium qubit into a frequency-resolved charge sensor. This
method results in a charge sensitivity of
, or an energy sensitivity (in joules per
hertz) of . This method rivals state-of-the-art transport-based
devices, while maintaining inherent insensitivity to DC charge noise. The high
charge sensitivity combined with large capacitive shunt unlocks new avenues for
exploring quantum phenomena in the range, such as the
strong-coupling regime with a resonant macroscopic mechanical resonator
Topological Photonics
Topology is revolutionizing photonics, bringing with it new theoretical
discoveries and a wealth of potential applications. This field was inspired by
the discovery of topological insulators, in which interfacial electrons
transport without dissipation even in the presence of impurities. Similarly,
new optical mirrors of different wave-vector space topologies have been
constructed to support new states of light propagating at their interfaces.
These novel waveguides allow light to flow around large imperfections without
back-reflection. The present review explains the underlying principles and
highlights the major findings in photonic crystals, coupled resonators,
metamaterials and quasicrystals.Comment: progress and review of an emerging field, 12 pages, 6 figures and 1
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