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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.

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 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).

We describe an experimental setup for producing a large cold erbium (Er) sample in a narrow-line magneto-optical trap (MOT) in a simple and efficient way. We implement a pair of angled slowing beams with respect to the Zeeman slower axis, and further slow down atoms exiting from the Zeeman slower. The second-stage slowing beams enable the narrow-line MOT to trap atoms exiting from the Zeeman slower with higher velocity. This scheme is particularly useful when the Zeeman slower is at low optical power without the conventional transverse cooling between an oven and a Zeeman slower, in which case we significantly improve the loading efficiency into the MOT and are able to trap more than 108 atoms in the narrow-line MOT of Er166. This work highlights our implementation, which greatly simplifies laser cooling and trapping of Er atoms and also should benefit other similar elements.

Recently Lanthanide atoms such as dysprosium and erbium have attracted significant attention in quantum simulation with ultracold atoms due to their large magnetic moment and meta-stable excited states. Here, we present our on-going efforts for developing a versatile erbium apparatus in which various exotic states of matter, such as quantum droplets, can be emulated. Slow erbium atoms generated by a spin-flip Zeeman slower are trapped by a magneto-optical trap (MOT). We implement a bi-chromatic MOT, consisting of singlet (4f 126s 2 3H6 → 4f 12( 3H6)6s6p( 1P1)) and triplet (4f 126s 2 3H6 → 4f 12( 3H6)6s6p( 3P1)) transitions, which increases the repetition rate of experiment. We will discuss experimental details that produce a degenerate quantum gas of erbium atoms in the apparatus.