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Accurately measuring magnetic fields is essential for magnetic-field sensitive experiments in areas like atomic, molecular, and optical physics, condensed matter experiments, and other areas. However, since many experiments are often conducted in an isolated environment that is inaccessible to experimentalists, it can be challenging to accurately determine the magnetic field at the target location. Here, we propose an efficient method for detecting magnetic fields with the assistance of an artificial neural network (NN). Instead of measuring the magnetic field directly at the desired location, we detect fields at several surrounding positions, and a trained NN can accurately predict the magnetic field at the target location. After training, we achieve a below 0.3% relative prediction error of magnetic field magnitude at the center of the vacuum chamber, and successfully apply this method to our erbium quantum gas apparatus for accurate calibration of magnetic field and long-term monitoring of environmental stray magnetic field. The demonstrated approach significantly simplifies the process of determining magnetic fields in isolated environments and can be applied to various research fields across a wide range of magnetic field magnitudes.

Lanthanide atoms with a large magnetic dipole moment, such as erbium and dysprosium, have attracted significant attention in quantum simulation benefitting from strong dipole-dipole interactions. Such long-ranged and anisotropic interaction gives rise to novel quantum states including quantum droplets and dipolar supersolids. However, while many predictions have been made on quasi-two dimensional dipolar Bose gases, such as anisotropic excitation spectrum and anisotropic coherence properties of superfluid, to date, experimental realization remains challenging. Here, we present the realization of quasi-two-dimensional dipolar Bose gas of erbium, where tight confinement is provided by an optical sheet trap and kinematically two-dimensional conditions are satisfied. To assess two-dimensional superfluidity arising from the Berezinsky-Kosterlitz-Thouless transition, we systematically monitor the momentum information of the sample by means of a momentum-focusing technique. Preliminary results will be discussed.

Collective light scattering in a Bose-Einstein condensate (BEC) has been extensively studied by using its unique coherence property. However, most experiments have explored superradiant light scattering with closed-shell atoms (e.g. alkali and alkaline-earth-like atoms) in the regime where only s-wave interactions are present. Here, we experimentally combine tunable s-wave scattering with dipolar interactions in a BEC of Er atoms. By tuning s-wave interaction strength through the Feshbach resonance, we tune the superradiance threshold with increasing phase fluctuations. We also observe an asymmetric superradiant scattering in a dipolar BEC by changing the direction of the external magnetic field. This collective light scattering opens a new way of probing dipolar quantum liquids in a BEC.

Superradiance is the coherent spontaneous emission from a many-body system, owing to its origin in the simultaneous cooperative interaction among its constituents, initially predicted by R. H. Dicke in 1954. It has been a subject of intense study in various systems, especially in atomic systems. In this poster, we will present our recent observation on superradiant light scattering in a dipolar Bose-Einstein condensate (BEC) of Er atoms [1]. We systematically investigate how s-wave and dipolar interactions affect superradiant light scattering. Our finding opens a new way of characterizing many-body quantum states with light scattering. As an example, we examine the collective light scatter across the phase transition from a dipolar BEC to a quantum droplet.

We report on the experimental realization of Bose–Einstein condensate (BEC) of 168Er atoms with tunable s-wave and dipolar interactions in a newly developed apparatus. Here, we describe an efficient method for trapping slow Er atoms in a narrow linewidth magneto-optical trap. After evaporative cooling in a crossed optical dipole trap, we achieve a spin-polarized condensate of > 2.5 × 10 4 atoms at the temperature of T≃ 50 nK. The efficient preparation of ultracold erbium bosons offers new possibilities for studying many-body physics with dipolar interactions. © 2023, The Korean Physical Society.

We demonstrate the existence of a dynamical phase transition in the quasi-one-dimensional photonic condensate system formed in an axially symmetric optical cavity filled with a suitable thermalizing medium. The dynamical transition is observed to occur between the periodically modulated superfluid phase and the superfluid droplets phase. The parameter domains and conditions leading to such a dynamical phase transition are identified. It is observed that such a transition in the system owes its origin to the collective photon dynamics rather than thermal or quantum effects. (C) 2021 Optical Society of America

We present a simple and effective method to implement an active stabilization of a diode laser with injection locking, which requires minimal user intervenes. The injection-locked state of the diode laser is probed by a photodetector, of which sensitivity is enhanced by a narrow laser-line filter. Taking advantage of the characteristic response of laser power to spectral modes from the narrow laser-line filter, we demonstrate that high spectral purity and low-intensity noise of the diode can be simultaneously maintained by active feedback to the injected laser. Our method is intrinsically cost-effective and does not require bulky devices, such as Fabry-Pérot interferometers or wavemeters, to actively stabilize the diode laser. Based on the successful implementation of this method in our quantum gas experiments, it is conceivable that our active stabilization will greatly simplify potential applications of injection locking of diode lasers in modularized or integrated optical systems. © 2021 Author(s).