Microwave spectroscopy and Zeeman effect of cesium (n+2)D5/2→nFJ(n+2)D_{5/2}\rightarrow nF_{J} Rydberg transitions

We report on high-resolution microwave spectroscopy of cesium Rydberg $(n+2)D_{5/2}\rightarrow nF_{J}$ transitions in a cold atomic gas. Atoms laser-cooled and trapped in a magnetic-optical trap are prepared in the $D$ Rydberg state using a two-photon laser excitation scheme. A microwave field transmitted into the chamber with a microwave horn drives the Rydberg transitions, which are probed via state selective field ionization. Varying duration and power of the microwave pulse, we observe Fourier side-band spectra as well as damped, on-resonant Rabi oscillations with pulse areas up to $\gtrsim 3 \pi$. Furthermore, we investigate the Zeeman effect of the clearly resolved $nF_J$ fine-structure levels in fields up to 120~mG, where the transition into $nF_{7/2}$ displays a thee-peak Zeeman pattern, while $nF_{5/2}$ shows a two-peak pattern. Our theoretical models explain all observed spectral characteristics, showing good agreement with the experiment. Our measurements provide a pathway for the study of high-angular-momentum Rydberg states, initialization and coherent manipulation of such states, Rydberg-atom macrodimers, and other Rydberg-atom interactions. Furthermore, the presented methods are suitable for calibration of microwave radiation as well as for nulling and calibration of DC magnetic fields in experimental chambers for cold atoms

Dephasing of ultracold cesium 80D5/280D_{5/2}-Rydberg Electromagnetically Induced Transparency

We study Rydberg electromagnetically induced transparency (EIT) of a cascade three-level atom involving 80$D_{5/2}$ state in a strong interaction regime employing a cesium ultracold cloud. In our experiment, a strong coupling laser couples 6$P_{3/2}$ to 80$D_{5/2}$ transition, while a weak probe, driving 6$S_{1/2}$ to 6$P_{3/2}$ transition, probes the coupling induced EIT signal. At the two-photon resonance, we observe that the EIT transmission decreases slowly with time, which is a signature of interaction induced metastability. The dephasing rate $\gamma_{\rm OD}$ is extracted with optical depth OD = $\gamma_{\rm OD}t$. We find that the optical depth linearly increases with time at onset for a fixed probe incident photon number $R_{\rm in}$ before saturation. The dephasing rate shows a nonlinear dependence on $R_{\rm in}$. The dephasing mechanism is mainly attributed to the strong dipole-dipole interactions, which leads to state transfer from $nD_{5/2}$ to other Rydberg states. We demonstrate that the typical transfer time $\tau_{0(80D)}$ obtained by the state selective field ionization technique is comparable with the decay time of EIT transmission $\tau_{0({\rm EIT})}$. The presented experiment provides a useful tool for investigating the strong nonlinear optical effects and metastable state in Rydberg many-body systems.Comment: 7 pages, 5 figure

Superradiance-induced multistability in one-dimensional driven Rydberg lattice gases

We study steady-state phases of a one-dimensional array of Rydberg atoms coupled by a microwave (MW) field where the higher-energy Rydberg state decays to the lower-energy one via single-body and collective (superradiant) decay. Using mean-field approaches, we examine the interplay among the MW coupling, intrastate van der Waals (vdW) interaction, and single-body and collective dissipation between Rydberg states. A linear stability analysis reveals that a series of phases, including uniform, antiferromagnetic, oscillatory, and bistable and multistable phases can be obtained. Without the vdW interaction, only uniform phases are found. In the presence of the vdW interaction, multistable solutions are enhanced when increasing the strength of the superradiant decay rate. Our numerical simulations show that the bistable and multistable phases are stabilized by superradiance in a long chain. The critical point between the uniform and multistable phases and its scaling with the atom number is obtained. Through numerically solving the master equation of a finite chain, we show that the mean-field multistable phase could be characterized by expectation values of Rydberg populations and two-body correlations between Rydberg atoms in different sites

Remediation of soil contaminated with decabrominated diphenyl ether using white rot fungi

Biodegradation of decabrominated diphenyl ether (BDE-209) in soil by white rot fungi under various experimental conditions was investigated in this study. It was found that BDE-209 in soil could be rapidly and efficiently degraded by white rot fungi, and the biodegradation fits the pseudo-first-order kinetics during a 15-day incubation period. The residues of BDE-209 in soil decreased with the increased amount of white rot fungi addition. It can be seen from the results that white rot fungi have a good degradation ability with one-step and two-step addition method. In native soil, the degradation of BDE-209 reached 52.65%, which was higher than that in sterilized soil. About 37.76–53.74% of BDE-209 degradation was observed in different soil types after 15 days. In addition, it was confirmed in this study that the presence of Cu2+, Cd2+ could enhance the remediation of soil contaminated with BDE-209, and the residues decreased by 69.20% and 54.65% for Cu2+ and Cd2+ treatment, respectively. However, the superior ability of white rot fungi to degrade BDE-209 was not obvious at low pollution level (<0.5 mg kg−1). First published online: 08 Feb 201

Digital common(s): the role of digital gamification in participatory design for the planning of high-density housing estates

“Digital Commons” explores the intersection between participatory design, digital gamification, and community engagement, contextualised in the planning of high-density housing estates in Hong Kong. The research project investigates how digital gamified participatory design can be applied in decision-making processes for the planning of public facilities in high-density housing estates. Focusing on community engagement methods, the project has engaged with residents of a case study housing estate, Jat Min Chuen in the Shatin Wai area of Hong Kong, to facilitate collective planning discussions about the past, present, and future of community facilities. Using a digital community game approach, it has collected opinions and needs from public housing residents, promoted collaborative design thinking processes, and provided a platform for participants to increase their understanding of the complexity of planning problems through 3D visualisation tools. The experiences documented in this study demonstrate how 3D interactivity, real-time engagement, and bottom-up perspectives may enhance the potential of using immersive digital twins during collective decision-making. The gaming outcomes show a high similarity across all teams in close relationship to users’ daily life routines, demonstrating a new powerful role for urban designers as a coordinator of interactive and collaborative planning processes

Dephasing of ultracold cesium 80D5/2-Rydberg electromagnetically induced transparency

We study Rydberg electromagnetically induced transparency (EIT) of a cascade three-level atom involving 80D5/2 state in a strong interaction regime employing a cesium ultracold cloud. In our experiment, a strong coupling laser couples 6P3/2 to 80D5/2 transition, while a weak probe, driving 6S1/2 to 6P3/2 transition, probes the coupling induced EIT signal. At the two-photon resonance, we observe that the EIT transmission decreases slowly with time, which is a signature of interaction induced metastability. The dephasing rate γOD is extracted with optical depth OD = γODt. We find that the optical depth linearly increases with time at onset for a fixed probe incident photon number Rin before saturation. The dephasing rate shows a nonlinear dependence on Rin. The dephasing mechanism is mainly attributed to the strong dipole-dipole interactions, which leads to state transfer from nD5/2 to other Rydberg states. We demonstrate that the typical transfer time τ0(80D) obtained by the state selective field ionization technique is comparable with the decay time of EIT transmission τ0(EIT). The presented experiment provides a useful tool for investigating the strong nonlinear optical effects and metastable state in Rydberg many-body systems

Dephasing of ultracold cesium 80í µí°· 5/2 -Rydberg Electromagnetically Induced Transparency

We study Rydberg electromagnetically induced transparency (EIT) of a cascade three-level atom involving 80í µí°· 5/2 state in a strong interaction regime employing a cesium ultracold cloud. In our experiment, a strong coupling laser couples 6í µí± 3/2 to 80í µí°· 5/2 transition, while a weak probe, driving 6í µí± 1/2 to 6í µí± 3/2 transition, probes the coupling induced EIT signal. At the two-photon resonance, we observe that the EIT transmission decreases slowly with time, which is a signature of interaction induced metastability. The dephasing rate í µí»¾ OD is extracted with optical depth OD = í µí»¾ OD í µí±¡. We find that the optical depth linearly increases with time at onset for a fixed probe incident photon number í µí± in before saturation. The dephasing rate shows a nonlinear dependence on í µí± in. The dephasing mechanism is mainly attributed to the strong dipole-dipole interactions, which leads to state transfer from í µí±í µí°· 5/2 to other Rydberg states. We demonstrate that the typical transfer time í µí¼ 0(80í µí°·) obtained by the state selective field ionization technique is comparable with the decay time of EIT transmission í µí¼ 0(EIT). The presented experiment provides a useful tool for investigating the strong nonlinear optical effects and metastable state in Rydberg many-body systems

Observation of Blackbody Radiation Enhanced Superradiance in Ultracold Rydberg Gases

An ensemble of excited atoms can synchronize emission of light collectively in a process known as superradiance when its characteristic size is smaller than the wavelength of emitted photons. The underlying superradiance depends strongly on electromagnetic (photon) fields surrounding the atomic ensemble. High mode densities of microwave photons from 300 K blackbody radiation (BBR) significantly enhance decay rates of Rydberg states to neighbouring states, enabling superradiance that is not possible with bare vacuum induced spontaneous decay. Here we report observations of the superradiance of ultracold Rydberg atoms embedded in a bath of room-temperature photons. The temporal evolution of the Rydberg |nD to |(n + 1)P superradiant decay of Cs atoms (n the principal quantum number) is measured directly in free space. Theoretical simulations confirm the BBR enhanced superradiance in large Rydberg ensembles. We demonstrate that the van der Waals interactions between Rydberg atoms change the superradiant dynamics and modify the scaling of the superradiance. In the presence of static electric fields, we find that the superradiance becomes slow, potentially due to many-body interaction induced dephasing. Our study provides insights into many-body dynamics of interacting atoms coupled to thermal BBR, and might open a route to the design of blackbody thermometry at microwave frequencies via collective, dissipative photon-atom interactions