Quantum Phase Transition in an Antiferromagnetic Spinor Bose-Einstein Condensate

We have experimentally observed the dynamics of an antiferromagnetic sodium Bose-Einstein condensate (BEC) quenched through a quantum phase transition. Using an off-resonant microwave field coupling the F = 1 and F = 2 atomic hyperfine levels, we rapidly switched the quadratic energy shift q from positive to negative values. At q = 0 the system undergoes a transition from a polar to antiferromagnetic phase. We measured the dynamical evolution of the population in the F = 1, m_F = 0 state in the vicinity of this transition point and observed a mixed state of all 3 hyperfine components for q < 0. We also observed the coarsening dynamics of the instability for q<0, as it nucleated small domains that grew to the axial size of the cloud

Strong Quantum Spin Correlations Observed in Atomic Spin Mixing

We have observed sub-Poissonian spin correlations generated by collisionally induced spin mixing in a spin-1 Bose-Einstein condensate. We measure a quantum noise reduction of -7 dB (-10 dB corrected for detection noise) below the standard quantum limit (SQL) for the corresponding coherent spin states. The spin fluctuations are detected as atom number differences in the spin states using fluorescent imaging that achieves a detection noise floor of 8 atoms per spin component for a probe time of 100 $\mu$s.Comment: 5 pages, 4 figure

Antiferromagnetic Spatial Ordering in a Quenched One-dimensional Spinor Gas

We have experimentally observed the emergence of spontaneous antiferromagnetic spatial order in a sodium spinor Bose-Einstein condensate that was quenched through a magnetic phase transition. For negative values of the quadratic Zeeman shift, a gas initially prepared in the F = 1, mF = 0 state collapsed into a dynamically evolving superposition of all 3 spin projections, mF = 0, +/-1. The quench gave rise to rich, nonequilibrium behavior where both nematic and magnetic spin waves were generated. We characterized the spatiotemporal evolution through two particle correlations between atoms in each pair of spin states. These revealed dramatic differences between the dynamics of the spin correlations and those of the spin populations

A noise-immune cavity-assisted non-destructive detection for an optical lattice clock in the quantum regime

We present and implement a non-destructive detection scheme for the transition probability readout of an optical lattice clock. The scheme relies on a differential heterodyne measurement of the dispersive properties of lattice-trapped atoms enhanced by a high finesse cavity. By design, this scheme offers a 1st order rejection of the technical noise sources, an enhanced signal-to-noise ratio, and an homogeneous atom-cavity coupling. We theoretically show that this scheme is optimal with respect to the photon shot noise limit. We experimentally realize this detection scheme in an operational strontium optical lattice clock. The resolution is on the order of a few atoms with a photon scattering rate low enough to keep the atoms trapped after detection. This scheme opens the door to various different interrogations protocols, which reduce the frequency instability, including atom recycling, zero-dead time clocks with a fast repetition rate, and sub quantum projection noise frequency stability

Generation and detection of a sub-Poissonian atom number distribution in a one-dimensional optical lattice

We demonstrate preparation and detection of an atom number distribution in a one-dimensional atomic lattice with the variance $-14$ dB below the Poissonian noise level. A mesoscopic ensemble containing a few thousand atoms is trapped in the evanescent field of a nanofiber. The atom number is measured through dual-color homodyne interferometry with a pW-power shot noise limited probe. Strong coupling of the evanescent probe guided by the nanofiber allows for a real-time measurement with a precision of $\pm 8$ atoms on an ensemble of some $10^3$ atoms in a one-dimensional trap. The method is very well suited for generating collective atomic entangled or spin-squeezed states via a quantum non-demolition measurement as well as for tomography of exotic atomic states in a one-dimensional lattice

Photoassociation spectroscopy of a Spin-1 Bose-Einstein condensate

We report on the high resolution photoassociation spectroscopy of a $^{87}$Rb spin-1 Bose-Einstein condensate to the $1_\mathrm{g} (P_{3/2}) v = 152$ excited molecular states. We demonstrate the use of spin dependent photoassociation to experimentally identify the molecular states and their corresponding initial scattering channel. These identifications are in excellent agreement with the eigenvalues of a hyperfine-rotational Hamiltonian. Using the observed spectra we estimate the change in scattering length and identify photoassociation laser light frequency ranges that maximize the change in the spin-dependent mean-field interaction energy.Comment: 5 pages, 4 figure

Spin-Nematic Squeezed Vacuum in a Quantum Gas

Using squeezed states it is possible to surpass the standard quantum limit of measurement uncertainty by reducing the measurement uncertainty of one property at the expense of another complementary property. Squeezed states were first demonstrated in optical fields and later with ensembles of pseudo spin-1/2 atoms using non-linear atom-light interactions. Recently, collisional interactions in ultracold atomic gases have been used to generate a large degree of quadrature spin squeezing in two-component Bose condensates. For pseudo spin-1/2 systems, the complementary properties are the different components of the total spin vector , which fully characterize the state on an SU(2) Bloch sphere. Here, we measure squeezing in a spin-1 Bose condensate, an SU(3) system, which requires measurement of the rank-2 nematic or quadrupole tensor as well to fully characterize the state. Following a quench through a nematic to ferromagnetic quantum phase transition, squeezing is observed in the variance of the quadratures up to -8.3(-0.7 +0.6) dB (-10.3(-0.9 +0.7) dB corrected for detection noise) below the standard quantum limit. This spin-nematic squeezing is observed for negligible occupation of the squeezed modes and is analogous to optical two-mode vacuum squeezing. This work has potential applications to continuous variable quantum information and quantum-enhanced magnetometry

Virtuelles Qualitätsmanagement - Strategien für den Aufbau abweichungsbetrachtender Simulationsmodelle und die Entwicklung virtueller Qualitätsmanagementtechniken

The potential of simulation-based process planning is not fully tapped by far! Impacts caused by the environment and the imperfection of manufacturing processes are often disregarded within simulation models in order to reduce their complexity. Thus manageable models are available, but conclusions concerning optimal process parameters or the quality capability of the new process chain are useless in most cases, by the reason of inadequate detailing of the model, or bear large ranges of uncertainty. Not before the real production line was set up, quality management techniques are getting realized in the ramp-up phase or in the beginning of the series production, when many operational determinations have already been made so far and many basic conditions have to be accepted as unchangeable in the economic view. Basing on that situation, the aim of this work is the development of a methodology called “virtual Quality Management”. It contains “coordinated approaches to the efficient modelling, adaptation, utilization and analysis of simulation studies for generating resilient knowledge and dimensioning quality techniques for products and processes during the planning stage”. The approach consists of a superordinate, universal methodology for the set up of deviation-concerning simulation models as well as of a reference model for the development and implementation of virtual quality management techniques. As part of an extensive evaluation, three simulation models from varying manufacturing sectors were set up and successfully examined by the use of the newly developed tools of the virtual statistic process control.Simulationsgestützte Prozessplanung birgt derzeit noch ein hohes Einsatzpotential! Bisher herrscht die Praxis vor, Umwelteinflüsse und Unvollkommenheiten des Fertigungsprozesses bei der Modellbildung zu vernachlässigen, um die Komplexität der Modelle einzugrenzen. Dadurch erhält man zwar überschaubare Modelle, aber Aussagen über optimale Prozessparameter oder die Qualitätsfähigkeit des zu planenden Prozesses sind aufgrund der unzureichenden Modelldetaillierung unbrauchbar oder weisen zu große Unsicherheiten auf. Oftmals werden erst nach dem realen Aufbau der Fertigungslinie die entsprechenden Qualitätsmanagementtechniken „aufpfropfend“ eingesetzt, wenn eine Vielzahl von begrenzenden Faktoren unter wirtschaftlichen Gesichtspunkten bereits als unveränderbar hingenommen werden müssen. Auf Basis der dargestellten Situation liegt das Ziel dieser Arbeit in der Bereitstellung einer Systematik, die mit dem Begriff „virtuelles Qualitätsmanagement“ betitelt wurde. Hierunter werden „aufeinander abgestimmte Vorgehensweisen zur effizienten Modellierung, Anpassung, Nutzung und Auswertung von Simulationen bezüglich Generieren von belastbarem Wissen und Auslegen von Qualitätstechniken für Produkte und Prozesse während der Planungsphase“ zusammengefasst. Der Ansatz besteht aus einer übergeordneten, allgemeingültigen Systematik für den Aufbau von abweichungsbetrachtenden Simulationsmodellen sowie aus einem Referenzmodell zur Entwicklung und Implementierung virtueller Qualitätsmanagementtechniken. Im Rahmen einer ausführlichen Erprobung wurden drei Simulationsmodelle unterschiedlicher Fachdomänen aufgebaut und mit den neu entwickelten Werkzeugen der virtuellen statistischen Prozessregelung erfolgreich untersucht

Spinor Bose-Einstein condensates

An overview on the physics of spinor and dipolar Bose-Einstein condensates (BECs) is given. Mean-field ground states, Bogoliubov spectra, and many-body ground and excited states of spinor BECs are discussed. Properties of spin-polarized dipolar BECs and those of spinor-dipolar BECs are reviewed. Some of the unique features of the vortices in spinor BECs such as fractional vortices and non-Abelian vortices are delineated. The symmetry of the order parameter is classified using group theory, and various topological excitations are investigated based on homotopy theory. Some of the more recent developments in a spinor BEC are discussed.Comment: To appear in Physics Reports. The PDF file with high resolution figures is available from the following website: http://cat.phys.s.u-tokyo.ac.jp/publication/review_of_spinorBEC.pd

FLAIR #1: semantic segmentation and domain adaptation dataset

The French National Institute of Geographical and Forest Information (IGN) has the mission to document and measure land-cover on French territory and provides referential geographical datasets, including high-resolution aerial images and topographic maps. The monitoring of land-cover plays a crucial role in land management and planning initiatives, which can have significant socio-economic and environmental impact. Together with remote sensing technologies, artificial intelligence (IA) promises to become a powerful tool in determining land-cover and its evolution. IGN is currently exploring the potential of IA in the production of high-resolution land cover maps. Notably, deep learning methods are employed to obtain a semantic segmentation of aerial images. However, territories as large as France imply heterogeneous contexts: variations in landscapes and image acquisition make it challenging to provide uniform, reliable and accurate results across all of France. The FLAIR-one dataset presented is part of the dataset currently used at IGN to establish the French national reference land cover map "Occupation du sol \`a grande \'echelle" (OCS- GE).Comment: Data access updat