Nonequilibrium dynamics are closely related to various fields of research, in which vastly different phases emerge when parameters are changed. However, it is difficult to construct nonequilibrium systems that have sufficiently tunable controllable parameters. Using microwave field coupling induced optical bistability, Rydberg gases exhibit a range of significantly different optical responses. In conjunction with electromagnetically induced transparency, the microwave coupling can create versatile nonequilibrium dynamics. In particular, the microwave coupling of two Rydberg states provides an additional handle for controlling the dynamics. And the microwave-controlled nonequilibrium phase transition has the potential to be applied in microwave field measurement. This study opens a new avenue to exploring bistable dynamics using microwave-coupled Rydberg gases, and developing quantum technological applications.

The effective lifetime of ultra-cold atoms in specific quantum states plays a crucial role in studying interaction parameters within quantum systems. Measuring the effective lifetime of various quantum states within ultra-cold atoms is a fundamental task in quantum operations. In this paper, the effective lifetimes of the excited electronic states F=2,mF=−2, F=2,mF=−1, and F=2,mF=0 for a sodium atomic Bose–Einstein condensate (BEC) are investigated in both the optical dipole trap (ODT) and one-dimensional optical lattice. Through the analysis of experimental data, we demonstrate the significant advantage of lattice loading over the optical dipole trap in terms of atomic lifetimes. The results provide crucial insights into the temporal scales relevant for investigating the evolution of boson gases in optical lattices, facilitating the realization of quantum simulations pertaining to unique quantum phases, and providing an important experimental basis for the research of non-equilibrium dynamics between different spin states.

Defect-free atom arrays provide new possibilities for exploring exotic quantum phenomena and realizing quantum computing. However, quickly and efficiently preparing defect-free atom arrays poses challenges. This paper proposes an innovative parallel rearrangement method, namely the parallel compression filling algorithm (PCFA), wherein multiple movable optical tweezers operate simultaneously. By limiting the shape of the initial loading, the method reduces movement complexity. The simulation comparisons show that this algorithm is more efficient in preparing defect-free atom arrays and can also be applied to the generation of other periodic structure arrays. The simulation results show that, in most cases, preparing a defect-free array of 400 atoms requires no more than 30 steps.

We report an experimental study of the highly excited 3(1)Delta(g) and 4(1)Delta(g) electronic states of the Rb2 molecule. Rovibrational levels of the two electronic states were probed using the high-resolution optical-optical double resonance technique by exciting Rb-85(2) molecules from thermally populated levels of the X-1 Sigma(+)(g) ground state through intermediate levels of the B-1 Pi(u) electronic state. The (1)Delta(g) resonances induced by the probe laser were observed by detecting laser induced fluorescence from collisionally populated triplet states lying near the upper (1)Delta(g) states to the a(3)Sigma(+)(u) triplet ground state. The (1)Delta(g) character of the two electronic states was confirmed by showing that the probe transitions to these states abide by (1)Delta <-(1)Pi dipole selection rules and by observing that their lowest rotational level is J=2. A set of molecular constants and a Rydberg-Klein-Rees potential-energy curve were calculated from the observed term values for each electronic state and compared with ab initio predictions.

The simulation of the predissociation spectrum of the Na2 23Πg∼33Πg←b3Πu (v=14,J=14) transition, observed earlier with the Perturbation Facilitated Optical–Optical Double Resonance (PFOODR) experimental method, is done within the Optimizer project with our Split-operator computational package using Padé approximations for all functions involved in the model. This simulation reproduces the experimental spectrum satisfactory well. The parameters of the model functions involved in the simulations are determined and reported. A brief description of our computational methods and programs is presented.

We report an experimental study of the highly excited $3{\phantom{\rule{0.16em}{0ex}}}^{1}{\mathrm{\ensuremath{\Delta}}}_{g}$ and $4{\phantom{\rule{0.16em}{0ex}}}^{1}{\mathrm{\ensuremath{\Delta}}}_{g}$ electronic states of the ${\mathrm{Rb}}_{2}$ molecule. Rovibrational levels of the two electronic states were probed using the high-resolution optical-optical double resonance technique by exciting $^{85}{\mathrm{Rb}}_{2}$ molecules from thermally populated levels of the $X{\phantom{\rule{0.16em}{0ex}}}^{1}{\mathrm{\ensuremath{\Sigma}}}_{g}^{+}$ ground state through intermediate levels of the $B{\phantom{\rule{0.16em}{0ex}}}^{1}{\mathrm{\ensuremath{\Pi}}}_{u}$ electronic state. The $^{1}\mathrm{\ensuremath{\Delta}}_{g}$ resonances induced by the probe laser were observed by detecting laser induced fluorescence from collisionally populated triplet states lying near the upper $^{1}\mathrm{\ensuremath{\Delta}}_{g}$ states to the ${a\phantom{\rule{0.16em}{0ex}}}^{3}{\mathrm{\ensuremath{\Sigma}}}_{u}^{+}$ triplet ground state. The $^{1}\mathrm{\ensuremath{\Delta}}_{g}$ character of the two electronic states was confirmed by showing that the probe transitions to these states abide by ${}^{1}\mathrm{\ensuremath{\Delta}}\ensuremath{\leftarrow}{\phantom{\rule{0.16em}{0ex}}}^{1}\mathrm{\ensuremath{\Pi}}$ dipole selection rules and by observing that their lowest rotational level is $J=2$. A set of molecular constants and a Rydberg-Klein-Rees potential-energy curve were calculated from the observed term values for each electronic state and compared with ab initio predictions.

Diode-pumped alkali lasers, possessing high efficiency and narrow linewidth, can provide feasible solutions for wavelength ranges difficult to reach by commercial lasers. In this study, we investigate a generation of coherent blue light (CBL) via four-wave mixing (FWM)-based up-conversion processes in cesium (Cs) vapor. A bichromatic pumping scheme with 852- and 917-nm lasers drives the Cs atoms to the 6D5/2 excited level, followed by cascaded decay of 6D5/2 → 7P3/2 → 6S1/2, producing 456-nm CBL under phase matching conditions. The fluorescence in multiple bands from blue to near- and far-infrared in the FWM process is demonstrated under different experimental conditions. To optimize the experimental parameters, we investigate the dependence of 456-nm CBL on the vapor temperature, frequency, and intensity of the two pump lasers. A maximum power of 2.94 mW is achieved with pump powers of 430 mW (for 852 nm) and 470 mW (for 917 nm). The corresponding conversion efficiency is 1.5%/W, three-fold higher than those in previous studies. Our results can contribute to fundamental research on atom−photon interactions and quantum metrology.

In order to model the spectroscopic and scattering properties of a quantum system, we propose and explore a new absorbing complex-type optical potential based on a combination of cosine functions. This function provides a high degree of smoothness to joint with a physical real-type potential. The capabilities of this function are investigated in terms of its effect on otherwise freely evolving quantum dynamics. We use our open-source programs to implement the Fourier Grid method with the Optimizer package (in Matlab), freely available at https://sourceforge.net/projects/optimizer-sovkov/ https://sourceforge.net/projects/optimizer-sovkov/. Keywords: quantum dynamics; damping boundary conditions; optical potential; Fourier Grid method; spectroscopy of ultracold ensembles.

Parametric modulation is an effective tool to measure the trap frequency and investigate the atom dynamics in an optical dipole trap or lattices. Herein, we report on experimental research of parametric resonances in an optical dipole trap. By modulating the trapping potential, we have measured the atomic loss dependence on the frequency of the parametric modulations. The resonance loss spectra and the evolution of atom populations at the resonant frequency have been demonstrated and compared under three modulation waveforms (sine, triangle and square waves). A phenomenological theoretical simulation has been performed and shown good accordance with the observed resonance loss spectra and the evolution of atom populations. The theoretical analysis can be easily extended to a complex waveform modulation and reproduce enough of the experiments.

Bose–Einstein condensates (BEC) of sodium atoms are transferred into one-dimensional (1D) optical lattice potentials, formed by two laser beams with a wavelength of 1064 nm, in a shallow optical trap. The phase coherence of the condensate in the lattice potential is studied by changing the lattice depth. A qualitative change in behavior of the BEC is observed at a lattice depth of ∼ 13.7 E r , where the quantum gas undergoes a transition from a superfluid state to a state that lacks well-to-well phase coherence.

In order to model the spectroscopic and scattering properties of a quantum system, we propose and explore a new absorbing complex-type optical potential based on a combination of cosine functions. This function provides a high degree of smoothness to joint with a physical real-type potential. The capabilities of this function are investigated in terms of its effect on otherwise freely evolving quantum dynamics. We use our open-source programs to implement the Fourier Grid method with the Optimizer package (in Matlab), freely available at https://sourceforge.net/projects/optimizer-sovkov/

We report the high-resolution photoassociation (PA) spectroscopy of 23Na excited from the spin-1 Bose-Einstein Condensate (BEC) to the molecular state of 0g-(P3/2)v = 4 and 1g(P3/2)v = 91. By comparing the PA spectra of different spin configurations, we experimentally studied the effect of spin on the PA spectra. The experimental spectra comply well with the theoretical consideration. The results will play an important role in the study of the spin interaction and control of the antiferromagnetism in Na.

This paper reports a high-resolution experimental study of the 3(3)Pi(g) and 4(3)Sigma(+)(g) electronic states of the Rb-85(2) dimer. In the experiment, rovibrational levels of the two electronic states were probed using the perturbation facilitated optical-optical double resonance technique by exciting Rb-85(2) molecules from thermally populated levels of the ground X-1 Sigma(+)(g) state through intermediate levels of the mixed A1 Sigma(+)(u) similar to b(3)Pi(u) electronic states. The resonances of the probe laser were observed by detecting the laser induced fluorescence from the target states to the a a(3)Sigma(+)(u) triplet ground state. In addition, to confirm the triplet character as well as the vibrational quantum number assignment of the states, for selected resonances the fluorescence to the a(3)Sigma(+)(u) state was resolved and bound-free spectra were recorded. From the observed term values for each state potential-energy curves were constructed using the Rydberg-Klein-Rees method.

This paper reports a high-resolution experimental study of the $3^{3}\mathrm{\ensuremath{\Pi}}_{g}$ and $4^{3}\mathrm{\ensuremath{\Sigma}}_{g}^{+}$ electronic states of the $^{85}\mathrm{Rb}_{2}$ dimer. In the experiment, rovibrational levels of the two electronic states were probed using the perturbation facilitated optical-optical double resonance technique by exciting $^{85}\mathrm{Rb}_{2}$ molecules from thermally populated levels of the ground $X^{1}\mathrm{\ensuremath{\Sigma}}_{g}^{+}$ state through intermediate levels of the mixed $A^{1}\mathrm{\ensuremath{\Sigma}}_{u}^{+}\ensuremath{\sim}b^{3}\mathrm{\ensuremath{\Pi}}_{u}$ electronic states. The resonances of the probe laser were observed by detecting the laser induced fluorescence from the target states to the $a^{3}\mathrm{\ensuremath{\Sigma}}_{u}^{+}$ triplet ground state. In addition, to confirm the triplet character as well as the vibrational quantum number assignment of the states, for selected resonances the fluorescence to the $a^{3}\mathrm{\ensuremath{\Sigma}}_{u}^{+}$ state was resolved and bound-free spectra were recorded. From the observed term values for each state potential-energy curves were constructed using the Rydberg-Klein-Rees method.

A B S T R A C T Experimental measurement and analysis of the laser-induced frequency shifts (LIFSs) of photoassociation (PA) spectra in a spinor Bose-Einstein condensate (BEC) of sodium is reported. The trap loss spectra of the atoms in the BEC were recorded at different PA laser intensities. Linear variations of the frequency shift for different spin components were demonstrated. The analogous linear dependence on the intensity of the full width at half maximum (FWHM) of the spectra was also shown. The slopes of the linear relationships of the shift and broadening are both independent of spin component within the error range of the experiment. A theoretical model, considering the interactions of three channels (a scattering continuum state, a single bound level near the scattering state, and an optically excited light-dressed level), explains the linear dependence of the LIFSs and the FWHM broadening on the PA laser power. The experimental results are consistent with the theoretical calculations. (c) 2021 Elsevier Ltd. All rights reserved.

We develop a research of spin currents in a 23 Na spinor Bose–Einstein condensate（BEC） by applying a magnetic field gradient. The spin current is successfully induced by the spin-dependent force arising from the magnetic field gradient. The dynamics of the spin components under the magnetic force is investigated. The study is promising to be extended to produce a longer spin-coherence and to enhance the sensitivity of the spin-mixing interferometry in a spinor BEC.

Obtaining effective spontaneous radiative transition channels is a fundamental topic in the preparation of ultracold rovibrational ground states of molecules. Herein, the ranges of prospective transition channels in the NaCs dimer are predicted via exploring the complex energy level structure and transition properties. The potential energy curves of Lambda-S states and Omega states, spectroscopy constants, absolute energies of bound states, and transition information (Frank-Condon factors, lifetimes, transition dipole moments) have been researched. With this purpose, the results of our experiment on binding energies of the b(3)Pi(0)+ rovibrational states are analyzed; the transition from the higher (photoassociated) (1)Pi state to the ground X-1 Sigma(+) state is discussed. The wavelengths of the two lasers are predicted as 622.8-656.7 nm and 896.3-969.8 nm with the B-1 Pi(1) and c(3)Sigma(+)(1) states, respectively, for the stimulated raman adiabatic passage method.

Herein, we report on the experimental observations and a quantitative determination of the laser-induced frequency shift (LIFS) in the photoassociation (PA) spectra of spinor Bose-Einstein condensate of sodium. Our investigations revealed a nonlinear dependence of the LIFS on the intensity of PA laser. By developing a model within the quadratic Stark effect, we simulate the experimental results via a theoretical model that confirms the former. The experimental observations and the theoretical analysis can further improve the accuracy of investigations on important molecular properties and on preparation of specific molecular states, with possible applications in various key fields.

We present an experiment for quickly producing Bose–Einstein condensates (BECs) of 23Na atoms in a simple crossed dipole trap. The atoms were collected in a magneto-optical trap from a zero-crossing Zeeman slower. The atoms are then transferred to a tightly focused crossed optical dipole trap, and a pure F = 1 BEC of ∼1.1 × 105 sodium atoms was created by a fast forced evaporation. Our system reliably generates the condensate at a rate exceeding 105 atoms every ∼8 s. We also compare the lifetimes of the mixed F = 1 condensate and the spin components (m F = 0, m F = +1).