Rb Atoms Research Articles

Optical and spin-selective time-of-flight measurement of light-induced desorption of Rb from Fe_3O_4 surfaces

Light-induced desorption of Rb atoms from a ferrimagnetic Fe_3O_4(001) surface was studied using a spin-selective optical method, which provides information on the spin polarization, velocity distribution, and amount of the desorbed atoms. The results showed that the intensity of the desorption of Rb from Fe_3O_4(001) induced by ultraviolet (UV) light irradiation was smaller than the detection limit at coverages lower than the threshold coverage at which the desorption rate began to increase. Moreover, the average magnetic quantum number of the desorbed atoms was smaller than that of electrons at the Fermi level of the Fe_3O_4(001) surface. These indicate that the light-induced desorption of Rb from an Fe_3O_4(001) surface occurs only in the high-coverage region in which the desorbing atoms are not in contact with the Fe_3O_4 surface, and that the desorption does not involve spin transfer.

Accurate and fast measurement of alkali-metal and noble-gas atoms spin polarizability based on frequency response in SERF co-magnetometer

Accurate and fast measurement of the spin polarizability of alkali-metal and noble-gas atoms in co-magnetometer is essential to improve the sensitivity of ultra-sensitive inertial measurements. We establish a frequency response model of K-Rb-21Ne spin strongly coupled ensembles, based on this we present a method for simultaneously measuring the spin polarization of 21Ne and Rb atoms. By applying magnetic field in y-direction oscillating at a fixed frequency, the z-axis main magnetic field value is changed linearly at the same time, the polarizability of Rb and 21Ne spins can be simultaneously obtained. The experimental results were highly consistent with analytical results. By applying a gradient magnetic field to amplify the effect of atomics depolarization, the self-compensating magnetic field points and atomic ensemble polarizability were measured three times continuously using our method and another method. The results proved that this method has fast measurement speed, high accuracy, and low influence on spin polarisation.

Effects of neighboring transitions on electromagnetically induced absorption and transparency in 87Rb atoms with respect to varying hyperfine spacings

Effects of neighboring transitions through Doppler broadening on electromagnetically induced absorption (EIA) and electromagnetically induced transparency (EIT) of the degenerate two-level system at the F g =2→F e =1,2, and 3 transitions of the 87Rb D2 line have been investigated. Two different polarization configurations, such as linear parallel and linear perpendicular polarizations of coupling and probe lasers, have been studied. We study the significant variation of EIT and EIA due to the effect of the neighboring transitions via artificial variation of the hyperfine spacings of the 5P3/2 state. We have a new observation such as EIT instead of EIA due to the neighboring effect, even in the case of closed systems such as F g =2→F e =3 of 87Rb for the linear parallel configuration, for the first time to our best knowledge. The observed spectra match well with theoretically calculated spectra. EIAs for the open F g =2→F e =1 and 2 transitions at the linear perpendicular polarization are observed due to neighboring effects. This system may be applied to optical switching systems for future quantum processing application.

Steering photoassociation of cold 85Rb atoms by two-color slowly-turned-on and rapidly-turned-off laser pulses

Photoassociation (PA) of 85Rb atoms from the ground state to the excited and states by two-color laser pulses at 100 is investigated by using quantum wavepacket method. Two pulses with detunings δ 1 and δ 2 varying from −1.0 to 1. cm−1 are taken into account. The specific case is generalized to the condition of arbitrary combination of δ 1 and δ 2 for both the Gaussian-pulse field and the slowly-turned-on and rapidly-turned-off (STRT) field. It is found that the introduce of the detunings in the two pluses can enhance the asymmetry of the time profile and broaden the linewidth of the laser field. The two factors can further enhance the PA probability for both resonant and nonresonant regions. Compared to the Gaussian field, the STRT field which is even more asymmetric in time profile and more broaden in linewidth can significantly enhance the PA probability, with the nonresonant transition dominating the PA process. It can be expected that once the two detunings are both positive, which is a relatively loose restriction for coherent control, a considerable PA probability can be obtained in a two-color STRT field.

Research on the noise characteristics of a closed-loop 87Rb atom comagnetometer

Spin-based comagnetometers have essential applications in studying new physical effects such as the fifth force, Lorentz violations, and spin-gravity interactions. In this paper, a transfer function model of the spin precession phase (frequency) is derived to analyze the comagnetometer's noise mechanism. The theory combined with experiments reveals that the output frequency noise of the spin oscillator above 5 Hz is mainly phase noise from the phase-locked loop. The noise below 5 Hz is mainly from the biased magnetic field noise. When building a comagnetometer using two spin oscillators, the symmetry of the spin oscillator is significant. When the intrinsic physical parameters cannot be symmetrical, the comagnetometer's common-mode suppression capability to magnetic field fluctuations can be enhanced by optimizing the control parameters. In addition, the closed-loop control of Bz can significantly weaken the effect of system asymmetry in the low-frequency band. Finally, when considering the comagnetometer system in nuclear magnetic resonance gyroscopes, a trade-off between the bandwidth and sensitivity can be achieved using theory. This paper is an excellent reference for both the research and application of comagnetometers.

Faraday polarization rotation control of 1529 nm wavelength between excited states of Rb atoms

Faraday polarization rotation control of 1529 nm wavelength has been obtained using the 5S1/2→5P3/2→4D5/2 transition of rubidium. The traditional off-resonant polarization rotation method commonly used in the Faraday effect for direct transitions of atoms is not applicable to the transitions between excited states. In this study, we proposed a near-resonant polarization rotation method using the Faraday effect between excited states of atoms, by which the polarization rotation of the rubidium 5P3/2→4D5/2 transition can be controlled from 0° to 90° with low distortion. The 780 nm pump light corresponding to the 5S1/2→5P3/2 transition can also be used simultaneously as a control source to manipulate the polarization state of the 1529 nm optical signal.

Non-adiabatic dynamical studies of the Rb(52P) + H2(X1[formula omitted]) → RbH(X1Σ+) + H(2s) reaction based on new diabatic potential energy surfaces

The reaction of Rb(52P) atom with H2 molecule is studied using time-dependent wave packet method based on the newly reported diabatic potential energy surfaces. The dynamics properties such as reaction probabilities, integral cross sections, differential cross sections (DCSs) and so on are calculated at state-to-state level of theory. In addition, the effect of vibrational excitation of reactant is considered in the calculations. The results indicate that the vibrational excitation of reactant can significantly increase the reaction probability and the RbH molecule is hardly formed when the reactant H2 molecule is in the ground state. The vibrational excitation of H2 molecule promotes the reaction more effectively than translational energy. The forward biased DCSs indicate that the stripping mechanism dominates the reaction.

Violation of Bell Inequality by Four‐Photon Greenberger‐Horne‐Zeilinger State with a Phase from a Warm Atomic Ensemble

AbstractA Greenberger–Horne–Zeilinger (GHZ) entangled state with a phase is crucial for realizing desired multipartite quantum states for practical applications. Here, it is reported that the violations of the general Bell inequality (GBI) introduced in using the four‐photon polarization‐entangled phase‐GHZ state realized via intrinsic polarization correlation and collective two‐photon coherence in the 5S1/2–5P3/2–5D5/2 transition of 87Rb atoms. The phase‐GHZ state can be achieved by the unitary transformation of only one local phase of the four photons. Theoretically, the GHZ state with the π/4 phase affords maximal violation of the GBI of 2√2 at the local measurement settings of the Pauli operators σx and σy. Strong violations of the GBI of the phase‐GHZ state by 47 standard deviations are experimentally demonstrated. In addition to the entanglement witness for the phase‐GHZ state, the results represent a genuine four‐photon entanglement of the phase‐GHZ state, thereby providing a novel resource for realizing photonic quantum computation, magic‐state distillation from entangled states, and quantum networks based on atom–photon interactions.

Detection of Entangled States Supported by Reinforcement Learning.

Discrimination of entangled states is an important element of quantum-enhanced metrology. This typically requires low-noise detection technology. Such a challenge can be circumvented by introducing nonlinear readout process. Traditionally, this is realized by reversing the very dynamics that generates the entangled state, which requires a full control over the system evolution. In this Letter, we present nonlinear readout of highly entangled states by employing reinforcement learning to manipulate the spin-mixing dynamics in a spin-1 atomic condensate. The reinforcement learning found results in driving the system toward an unstable fixed point, whereby the (to be sensed) phase perturbation is amplified by the subsequent spin-mixing dynamics. Working with a condensate of 10 900 ^{87}Rb atoms, we achieve a metrological gain of 6.97_{-1.38}^{+1.30} dB beyond the classical precision limit. Our work will open up new possibilities in unlocking the full potential of entanglement caused quantum enhancement in experiments.

Flying characterization of colliding partners by hyperfine splitting frequency of neutral paramagnetic atoms.

The pseudopotentials and dispersion potentials are applied to a theoretical study of the hyperfine splitting frequencies of the ground-state paramagnetic hydrogen (H) and alkali-metal (Li, Na, K, Rb, and Cs) atoms in noble gases (He, Ne, Ar, Kr, and Xe). Using classical turning points for statistical averages, we find that numerical calculations based on second-order perturbation theory fit the measured frequency shifts well over a wide temperature range. The characteristic energy, pseudopotential height, and electric-dipole polarizability allow us to consistently determine the van der Waals radii and electron scattering lengths of noble-gas atoms. This study shows that the hyperfine splitting frequency of alkali-metal atoms is a good measure for investigating colliding partners.

Potential Energy Surfaces and Arrangement Effects of RbNa2 Complex.

Ab initio calculations of alkaline diatomic molecule interactions with alkaline atoms provide detailed information about their electronic structure, vibrational frequencies, and spectroscopic properties, which are difficult to measure experimentally. This knowledge can aid in designing and interpreting experiments and guide the development of computational models and advanced dynamical calculation. Using the quantum chemistry ab initio methods based on multi-reference configuration interaction with Davidson correction (MCSCF/MRCI + Q), atomic effective core potentials, core-polarization potentials, and the interactions between the sodium atom and the NaRb diatomic molecule are investigated. To describe the potential energy surfaces of the RbNa2 system, we introduce two geometries described in the Z-matrix coordinates (Re, R, θ). Potential energy surfaces of the ground state 12A' and the first excited state 22A' were calculated for different approach directions of the sodium atom to the NaRb molecule and two geometries were considered. The first geometry is where the Na atom approaches the Rb atom of the RbNa dimer, and the second one is when it approaches the Na atom of the RbNa dimer. Global minima of the ground and first excited states and conical intersections between these states are determined for both geometries. The RbNa dimer in interaction with the sodium atom is found to be strongly attractive in its first excited state, which may be important for the experimenters particularly in the field of cold alkali polar dimers. Thereafter, the potential energy curves correlated to the lowest-lying dissociation limits are calculated in the linear form for the two geometrical cases (angle θ at 180°) and the atomic arrangement effect is observed.

First-principles study of electronic properties of two-dimensional metal mixed perovskites solar cell and water resistance performance

Two-Dimensional (2D) layered hybrid organic-inorganic perovskite (HOIP) materials have been considered as potential photoconductive materials for solar cells owing to extraordinary conversion efficiency and easy preparation process. In this study, we perform first-principles design on metal mixed 2D HOIPs (BA2(Cs1-x Rb x )2Sn1.5Pb1.5I10 with different proportions of composition (x = 0, 0.5 and 1)) to investigate their electronic properties and stability against moisture. We find that the band gap and effective mass of BA2(Cs1-x Rb x )2Sn1.5Pb1.5I10 increases as the concentrations of mixed Rb atoms increases. Moreover, the result of calculated adsorption energy indicates that the metal mixed 2D HOIPs with different composition ratios of Rb atom exhibit better capacity on the resistance of water than the pure one (BA2MA2Sn3I10). The metal mixed 2D HOIPs shows great potential to be a new generation of solar cell with low-cost, suitable band gap, high thermal stability, and desirable power conversion efficiency.

Accurate measurement of the loss rate of cold atoms due to background gas collisions for the quantum-based cold atom vacuum standard

We present the measurements of thermalized collisional rate coefficients for ultra-cold 7Li and 87Rb colliding with room-temperature He, Ne, N2, Ar, Kr, and Xe. In our experiments, a combined flowmeter and dynamic expansion system, a vacuum metrology standard, is used to set a known number density for the room-temperature background gas in the vicinity of the magnetically trapped 7Li or 87Rb clouds. Each collision with a background atom or molecule removes a 7Li or 87Rb atom from its trap, and the change in the atom loss rate with background gas density is used to determine the thermalized loss rate coefficients with fractional standard uncertainties better than 1.6% for 7Li and 2.7% for 87Rb. We find consistency—a degree of equivalence of less than one—between the measurements and recent quantum-scattering calculations of the loss rate coefficients [Kłos and Tiesinga, J. Chem. Phys. 158, 014308 (2023)], with the exception of the loss rate coefficient for both 7Li and 87Rb colliding with Ar. Nevertheless, the agreement between theory and experiment for all other studied systems provides validation that a quantum-based measurement of vacuum pressure using cold atoms also serves as a primary standard for vacuum pressure, which we refer to as the cold-atom vacuum standard.

An improved source of spin-polarized electrons based on spin exchange in optically pumped rubidium vapor

We have improved a polarized electron source in which unpolarized electrons undergo collisions with a mixture of buffer gas molecules and optically spin-polarized Rb atoms. With a nitrogen buffer gas, the source reliably provides spin polarization between 15% and 25% with beam currents >4 μA. Vacuum pump upgrades mitigate problems caused by denatured diffusion pump oil, leading to longer run times. A new differential pumping scheme allows the use of higher buffer gas pressures up to 800 mTorr. With a new optics layout, the Rb polarization is continuously monitored by a probe laser and improved pump laser power provides more constant high polarization. We have implemented an einzel lens to better control the energy of the electrons delivered to the target chamber and to preferentially select electron populations of higher polarization. The source is designed for studies of biologically relevant chiral molecule samples, which can poison photoemission-based GaAs polarized electron sources at very low partial pressures. It operates adjacent to a target chamber that rises to pressures as high as 10−4 Torr and has been implemented in a first experiment with chiral cysteine targets.

Magneto-optical trapping in a near-suface borehole.

Borehole gravity sensing can be used in a number of applications to measure features around a well, including rock-type change mapping and determination of reservoir porosity. Quantum technology gravity sensors, based on atom interferometry, have the ability to offer increased survey speeds and reduced need for calibration. While surface sensors have been demonstrated in real world environments, significant improvements in robustness and reductions to radial size, weight, and power consumption are required for such devices to be deployed in boreholes. To realise the first step towards the deployment of cold atom-based sensors down boreholes, we demonstrate a borehole-deployable magneto-optical trap, the core package of many cold atom-based systems. The enclosure containing the magneto-optical trap itself had an outer radius of (60 ± 0.1) mm at its widest point and a length of (890 ± 5) mm. This system was used to generate atom clouds at 1 m intervals in a 14 cm wide, 50 m deep borehole, to simulate how in-borehole gravity surveys are performed. During the survey, the system generated, on average, clouds of (3.0 ± 0.1) × 105 87Rb atoms with the standard deviation in atom number across the survey observed to be as low as 8.9 × 104.

Observation of Rydberg Blockade Due to the Charge-Dipole Interaction between an Atom and a Polar Molecule.

We demonstrate Rydberg blockade due to the charge-dipole interaction between a single Rb atom and a single RbCs molecule confined in optical tweezers. The molecule is formed by magnetoassociation of a Rb+Cs atom pair and subsequently transferred to the rovibrational ground state with an efficiency of 91(1)%. Species-specific tweezers are used to control the separation between the atom and molecule. The charge-dipole interaction causes blockade of the transition to the Rb(52s) Rydberg state, when the atom-molecule separation is set to 310(40)nm. The observed excitation dynamics are in good agreement with simulations using calculated interaction potentials. Our results open up the prospect of a hybrid platform where quantum information is transferred between individually trapped molecules using Rydberg atoms.

Accuracy Improvement of a Compact 85Rb Atom Gravimeter by Suppressing Laser Crosstalk and Light Shift

We design and implement a compact 85Rb atom gravimeter (AG). The diameter of the sensor head is 35 cm and the height is 65 cm; the optical and electronic systems are installed in four standard 3U cabinets. The measurement accuracy of this AG is improved by suppress laser crosstalk and light shift. In addition, the angle of the Raman laser reflector is adjusted and locked, and the attitude of the sensing head is automatically adjusted, and the vibration noise is also compensated. The comparison measurement results between this AG and the superconducting gravimeter indicate that its long-term stability is 0.65 μGal @50000 s.

Thermal contribution to measured g-factors in alkali atoms

In this paper, we consider a one-loop thermal correction to the g-factors of the ground and low-lying excited states in atomic systems with one valence s electron. As an example, we carried out calculations for Rb and Cs atoms, where optical measurements of transition frequencies set the metrological level of accuracy. With the development of atomic systems as the most accurate tool for spectroscopic experiments, it has become increasingly important to improve the accuracy of measuring the electron g-factor, which is currently at10−12. The rapid progress in this field in recent years requires analysis not only of various relativistic, quantum electrodynamics, and other effects, but also theoretical studies of phenomena stimulated by the external thermal environment. We can expect that the thermal contribution to the g-factor calculated in our work may be of interest in the near future.

420-nm Faraday Optical Filter With 2.7-MHz Ultranarrow Bandwidth Based on Laser Cooled 87Rb Atoms

Using laser cooling technology, we demonstrate an ultranarrow-bandwidth Faraday anomalous dispersion optical filter (FADOF) which operates on the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5^{2}\text{S}_{1/2}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$F = 2$ </tex-math></inline-formula> ) to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$6^{2}\text{P}_{3/2}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$F' = 3$ </tex-math></inline-formula> ) transition at 420 nm based on cold 87Rb atoms. The filter achieves a single 2.7(2) MHz passband at a peak transmission of 3.2%. It is the narrowest bandwidth FADOF known at present, as the influence of Doppler broadening on the bandwidth narrowing of FADOF is effectively overcome by cold atoms. This ultranarrow-bandwidth FADOF has a figure of merit (FOM) value of 11.85 GHz−1, which is seven times larger than the largest FOM achieved by thermal vapor atomic optical filter published to date. Furthermore, the scheme can be extended to almost all kinds of atomic optical filters and may find applications in active Faraday optical frequency standard and self-stabilizing laser.

Formation of Ultracold Molecules by Merging Optical Tweezers.

We demonstrate the formation of a single RbCs molecule during the merging of two optical tweezers, one containing a single Rb atom and the other a single Cs atom. Both atoms are initially predominantly in the motional ground states of their respective tweezers. We confirm molecule formation and establish the state of the molecule formed by measuring its binding energy. We find that the probability of molecule formation can be controlled by tuning the confinement of the traps during the merging process, in good agreement with coupled-channel calculations. We show that the conversion efficiency from atoms to molecules using this technique is comparable to magnetoassociation.