88 research outputs found
Engineering entanglement for metrology with rotating matter waves
Entangled states of rotating, trapped ultracold bosons form a very promising scenario for quantum metrology. In order to employ such states for metrology, it is vital to understand their detailed form and the enhanced accuracy with which they could measure phase, in this case generated through rotation. In this work, we study the rotation of ultracold bosons in an asymmetric trapping potential beyond the lowest Landau level (LLL) approximation. We demonstrate that while the LLL can identify reasonably the critical frequency for a quantum phase transition and entangled state generation, it is vital to go beyond the LLL to identify the details of the state and quantify the quantum Fisher information (which bounds the accuracy of the phase measurement). We thus identify a new parameter regime for useful entangled state generation, amenable to experimental investigation
Machine Learning (ML)-assisted Beam Management in millimeter (mm)Wave Distributed Multiple Input Multiple Output (D-MIMO) systems
Beam management (BM) protocols are critical for establishing and maintaining
connectivity between network radio nodes and User Equipments (UEs). In
Distributed Multiple Input Multiple Output systems (D-MIMO), a number of access
points (APs), coordinated by a central processing unit (CPU), serves a number
of UEs. At mmWave frequencies, the problem of finding the best AP and beam to
serve the UEs is challenging due to a large number of beams that need to be
sounded with Downlink (DL) reference signals. The objective of this paper is to
investigate whether the best AP/beam can be reliably inferred from sounding
only a small subset of beams and leveraging AI/ML for inference of best
beam/AP. We use Random Forest (RF), MissForest (MF) and conditional Generative
Adversarial Networks (c-GAN) for demonstrating the performance benefits of
inference
Quantum-enhanced gyroscopy with rotating anisotropic Bose–Einstein condensates
High-precision gyroscopes are a key component of inertial navigation systems. By considering matter wave gyroscopes that make use of entanglement it should be possible to gain some advantages in terms of sensitivity, size, and resources used over unentangled optical systems. In this paper we consider the details of such a quantum-enhanced atom interferometry scheme based on atoms trapped in a carefully-chosen rotating trap. We consider all the steps: entanglement generation, phase imprinting, and read-out of the signal and show that quantum enhancement should be possible in principle. While the improvement in performance over equivalent unentangled schemes is small, our feasibility study opens the door to further developments and improvements
Vortex nucleation in mesoscopic Bose superfluid and breaking of the parity symmetry
We analyze vortex nucleation in mezoscopic 2D Bose superfluid in a rotating
trap. We explicitly include a weakly anisotropic stirring potential, breaking
thus explicitly the axial symmetry. As the rotation frequency passes the
critical value the system undergoes an extra symmetry
change/breaking. Well below the ground state is properly described
by the mean field theory with an even condensate wave function. Well above
the MF solution works also well, but the order parameter becomes
odd. This phenomenon involves therefore a discrete parity symmetry breaking. In
the critical region the MF solutions exhibit dynamical instability. The true
many body state is a strongly correlated entangled state involving two
macroscopically occupied modes (eigenstates of the single particle density
operator). We characterize this state in various aspects: i) the eligibility
for adiabatic evolution; ii) its analytical approximation given by the
maximally entangled combination of two single modes; and finally iii) its
appearance in particle detection measurements.Comment: 14 pages, 27 figure
Particles in non-Abelian gauge potentials - Landau problem and insertion of non-Abelian flux
We study charged spin-1/2 particles in two dimensions, subject to a
perpendicular non-Abelian magnetic field. Specializing to a choice of vector
potential that is spatially constant but non-Abelian, we investigate the Landau
level spectrum in planar and spherical geometry, paying particular attention to
the role of the total angular momentum J = L +S. After this we show that the
adiabatic insertion of non-Abelian flux in a spin-polarized quantum Hall state
leads to the formation of charged spin-textures, which in the simplest cases
can be identified with quantum Hall Skyrmions.Comment: 24 pages, 10 figures (with corrected legends
Topological superfluids on a lattice with non-Abelian gauge fields
Two-component fermionic superfluids on a lattice with an external non-Abelian
gauge field give access to a variety of topological phases in presence of a
sufficiently large spin imbalance. We address here the important issue of
superfluidity breakdown induced by spin imbalance by a self-consistent
calculation of the pairing gap, showing which of the predicted phases will be
experimentally accessible. We present the full topological phase diagram, and
we analyze the connection between Chern numbers and the existence of
topologically protected and non-protected edge modes. The Chern numbers are
calculated via a very efficient and simple method.Comment: 6 pages, 5 figures to be published in Europhysics Letter
Subpixel translation of MEMS measured by discrete Fourier transform analysis of CCD images
We present a straightforward method for measuring in-plane linear displacements of microelectromechanical systems (MEMS) with a subnanometer resolution. The technique is based on Fourier transform analysis of a video recorded with a Charge-Coupled Device (CCD) camera attached to an optical microscope and can be used to characterize any device featuring periodic patterns along the direction of motion. Using a digital microscope mounted on a vibration isolation table, a subpixel resolution better than 1/100 pixel could be achieved, enabling quasi-static measurements with a resolution of 0.5 nm
Topological superfluid of spinless Fermi gases in p-band honeycomb optical lattices with on-site rotation
In this paper, we put forward to another route realizing topological
superfluid (TS). In contrast to conventional method, spin-orbit coupling and
external magnetic field are not requisite. Introducing an experimentally
feasible technique called on-site rotation (OSR) into p-band honeycomb optical
lattices for spinless Fermi gases and considering CDW and pairing on the same
footing, we investigate the effects of OSR on superfluidity. The results
suggest that when OSR is beyond a critical value, where CDW vanishes, the
system transits from a normal superfluid (NS) with zero TKNN number to TS
labeled by a non-zero TKNN number. In addition, phase transitions between
different TS are also possible
Tunnelling rates for the nonlinear Wannier-Stark problem
We present a method to numerically compute accurate tunnelling rates for a
Bose-Einstein condensate which is described by the nonlinear Gross-Pitaevskii
equation. Our method is based on a sophisticated real-time integration of the
complex-scaled Gross-Pitaevskii equation, and it is capable of finding the
stationary eigenvalues for the Wannier-Stark problem. We show that even weak
nonlinearities have significant effects in the vicinity of very sensitive
resonant tunnelling peaks, which occur in the rates as a function of the Stark
field amplitude. The mean-field interaction induces a broadening and a shift of
the peaks, and the latter is explained by analytic perturbation theory
Modal analysis and modeling of a frictionless electrostatic rotary stepper micromotor
We present the design, modeling and characterization of a 3-phase electrostatic rotary stepper micromotor. The proposed motor is a monolithic device fabricated using silicon-on-insulator (SOI) technology. The rotor is suspended with a frictionless flexural pivot bearing and reaches an unprecedented rotational range of 30° (+/- 15°) at 65 V. We have established a mechanical model of the deformation structure and performed finite element analysis (FEA) simulations of the dynamic properties. These studies are consistent with the extensive experimental characterization performed in the quasi-static, transient, and dynamic regimes
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