Two-dimensional atom localization via quantum interference in a coherently driven inverted-Y system

A scheme for two-dimensional (2D) subwavelength atom localization is proposed, in which the atom is in an inverted-Y configuration and driven by two orthogonal standing-wave lasers. Due to the spatial dependence of atom-field interaction, the quantities of system, including the frequency of spontaneously emitted photon, the population in the excited state, and the probe absorption, carry information about the position of atom in standing-wave fields. We exploit this fact to 2D atom localization, and obtain a high precision and resolution in the position probability distribution.     

Atom Localization Using a Rydberg State

A theoretical study is presented for two-dimensional (2D) and three-dimensional (3D) atom localization in a four-level atomic system involving a Rydberg state. The scheme is based on a mixture of two well-known V- and ladder-type systems illuminated by a weak probe field as well as control and switching laser beams of larger intensity, which could be standing waves. As a result of space-dependent atom? light interaction and due to the effect of Rydberg electromagnetically induced transparency or Rydberg electromagnetically induced absorption, various 2D and 3D localization structures appear. Specifically, the detecting probability and precision of 2D and 3D atom localization can be remarkably enhanced through suitable adjusting the controlling parameters of the system. The proposed scheme may provide a promising approach to achieve high precision and perfect resolution 2D and 3D atom localization.     

Two-dimensional atom localization via probe absorption in a four-level atomic system

We have investigated the two-dimensional (2D) atom localization via probe absorption in a coherently driven four-level atomic system by means of a radio-frequency field driving a hyperfine transition. It is found that the detecting probability and precision of 2D atom localization can be significantly improved via adjusting the system parameters. As a result, our scheme may be helpful in laser cooling or the atom nano-lithography via atom localization.     

Atom localization via controlled spontaneous emission in a five-level atomic system

We investigate the one- and two-dimensional atom localization behaviors via spontaneous emission in a coherently driven five-level atomic system by means of a radio-frequency field driving a hyperfine transition. It is found that the detecting probability and precision of atom localization behaviors can be significantly improved via adjusting the system parameters. More importantly, the two-dimensional atom localization patterns reveal that the maximal probability of finding an atom within the sub-wavelength domain of the standing waves can reach unity when the corresponding conditions are satisfied. As a result, our scheme may be helpful in laser cooling or the atom nano-lithography via atom localization.     

Efficient two-dimensional atom localization via spontaneous emission in a single decay channel

We investigate the two-dimensional atom localization behaviors in a four-level atomic system via controlled spontaneous emission in a single decay channel. It is found that the detecting probability and precision of atom localization behaviors can be significantly improved via adjusting the system parameters. More importantly, the two-dimensional atom localization patterns reveal that the maximal probability of finding an atom within the sub-half-wavelength domain of the standing waves can reach unity when the corresponding conditions are satisfied. As a result, our scheme may be helpful in laser cooling or the atom nano-lithography via atom localization.     

High-precision two-dimensional atom localization via probe absorption in an M-scheme atomic system

In the present paper, we investigate the behavior of two-dimensional atom localization in a five-level M-scheme atomic system driven by two orthogonal standing-wave fields. We find that the precision and resolution of the atom localization depends on the probe field detuning significantly. And because of the effect of the microwave field, an atom can be located at a particular position via adjusting the system parameters.     

Atom localization in a four-level atomic system with an assisting radio-frequency driven field

We propose a scheme for atom localization in a four-level atomic system by means of a radio-frequency field driving a hyperfine transition within the two ground states. It is found that, due to the quantum disturbed effect induced by the radio-frequency field, the property of atom localization can be significantly controlled. This scheme shows some characteristics that other schemes of atom localization do not have, which may provide some possibilities for the technological applications in atom nano-lithography.     

基于里德堡原子的电场测量

里德堡原子具有大的极化率、低的场电离阈值和大的电偶极矩,对外部电磁场十分敏感,可以用来测量电场强度特别是微波电场的强度. 利用里德堡原子的量子干涉效应(电磁诱导透明和Autler-Townes效应)测量微波电场强度的灵敏度远高于传统采用偶极天线测量微波电场的灵敏度. 此外,里德堡原子电场计 可以溯源到标准物理量,不需要额外校准; 采用玻璃探头,对待测电场干扰少; 灵敏度也不依赖于探头的物理尺寸. 同时,该电场计还可以实现对微波电场的偏振方向的测量, 实现亚波长和近场区域电场成像与测量. 通过选择不同的里德堡能级,可以实现1-500 GHz超宽频段范围内微波电场强度的测量. 主要综述基于里德堡原子的电场精密测量研究, 详细介绍了里德堡原子电场计的原理与实验进展, 并简单讨论了其发展方向.     

High-precision three-dimensional Rydberg atom localization in a four-level atomic system

Rydberg atoms have been widely investigated due to their large size, long radiative lifetime, huge polarizability and strong dipole-dipole interactions. The position information of Rydberg atoms provides more possibilities for quantum optics research, which can be obtained under the localization method. We study the behavior of three-dimensional(3 D)Rydberg atom localization in a four-level configuration with the measurement of the spatial optical absorption. The atomic localization precision depends strongly on the detuning and Rabi frequency of the involved laser fields. A 100% probability of finding the Rydberg atom at a specific 3 D position is achieved with precision of ～0.031λ. This work demonstrates the possibility for achieving the 3 D atom localization of the Rydberg atom in the experiment.     

Two-dimensional atom localization via Raman-driven coherence

A scheme for two-dimensional (2D) atom localization via Raman-driven coherence in a four-level diamond-configuration system is suggested. The atom interacts with two orthogonal standing-wave fields where each standing-wave field is constructed from the superposition of the two-standing wave fields along the corresponding directions. Due to the position-dependent atom–field interaction, the frequency of the spontaneously emitted photon carries the position information about the atom. We investigate the effect of the detunings and phase shifts associated with standing-wave fields. Unique position information of the single atom is obtained by properly adjusting the system parameters. This is an extension of our previous proposal for one-dimensional atom localization via Raman-driven coherence [1].     

Efficient two-dimensional atom localization via phase-sensitive absorption spectrum in a radio-frequency-driven four-level atomic system

A scheme of two-dimensional (2D) atom localization based on the phase-sensitive probe absorption is proposed in a four-level Λ-type atomic system with an assisting radio-frequency (rf)-driven field. The obtained 2D atom localization patterns reveal that the maximal probability of finding an atom within the sub-wavelength domain of the standing waves can arrive at unity by appropriate choice of the system parameters.     

Atom localization of a two-level pump-probe system via the absorption spectrum

We propose a scheme to localize a two-level atom inside a classical standing wave field conditioned upon the measurement of the frequency of a weak probe field at resonance excitation of a two-level atomic system. Inside the classical standing wave field, the interaction between the atom and the field is position-dependent due to the Rabi frequency of the driving field; hence, as the absorption frequency of the probe field is measured, the position of an atom inside the classical standing wave field will be determined. The effects of atomic parameters on atom localization are then discussed.     

Absorption properties of a driven Doppler—broadened ladder system with hyperfine structure

We have studied the absorption spectrum of a Doppler-broadened ladder system,where the highest level is coupled into two middle hyperfine sublevels by a strong coherent field.We find that,when the system is considered as homogeneous,either two or three spectral components are observed,depending on the detuning of the coherent field.but when the velocity distribution of atoms is considered,we can always observe one electromagnetically induced transparency (EIT) window with high dispersion.So the atomic hyperfine structure cannot be an impediment for obtaining EIT.     

Rydberg原子的微波电磁感应透明-Autler-Townes光谱

主要研究了室温下微波场缀饰的铯Rydberg原子的电磁感应透明-Autler-Townes(EIT-AT)光谱.首先,以铯原子6S_(1/2)→6P_(3/2)→50S_(1/2)形成阶梯型三能级系统,利用强耦合光作用于6P_(3/2)→50S_(1/2)的Rydberg跃迁,弱探测光耦合基态跃迁6S_(1/2)→6P_(3/2)并探测由耦合光形成的电磁感应透明(EIT)效应.然后,以频率为30.582 GHz的微波电场耦合相邻的Rydberg能级50S_(1/2)→50P_(1/2)产生微波AT分裂.利用Rydberg EIT探测微波耦合相邻Rydberg能级产生的AT分裂,形成EIT-AT光谱,进而实现微波电场的测量.当微波场的强度增加到一定值时,EIT-AT光谱表现为多峰光谱结构.分析EIT-AT多峰光谱的成因,发现这主要是由场的不均匀性导致的,一定的EIT-AT光谱特征对应于特定的非均匀场分布.研究表明,利用Rydberg EIT-AT光谱可以实现微波电场的测量,利用其光谱特征可实现微波场的实时监测,进而提出了一种提高微波场空间分辨率的测量方法.     

Dynamic Quantum Erasure Mediated by Electromagnetically Induced Transparency

We propose a scheme on control of the transition from quantum decoherence to coherence of a considered system S provided by the polarization degree of freedom of a probe field coupled to its motional degrees of freedom representing the environment B. A magneto-optically manipulated atomic ensemble with a tripod configuration is used to enhance the coupling between systems S and B. The spatial profile of the external fields induces a spatially varying potential for system B in the gas cell with identical and noninteracting atoms at different transverse points. It is found that the coherence of the system S can be maintained, lost or gained by properly choosing the incident positions of the probe field with respect to the center of the control laser field, and the two photon detuning for each components of the probe laser field.     

1D atom localization via probe absorption spectrum in a four-level cascade-type atomic system

We present a simple scheme of atom localization in a subwavelength domain via manipulation of probe absorption spectrum in a four-level atomic system. Due to the joint quantum interference induced by the standing-wave and radio-frequency driving fields, the localization peak position and number as well as the conditional position probability can be controlled by properly adjusting the system parameters. The proposed scheme may provide a promising way to achieve high-precision and high-resolution 1D atom localization.     

Atom localization via absorption spectrum

We propose a scheme to localize an atom in a three-level A-type configuration inside a classical standing wave field conditioned upon the measurement of frequency of a weak probe field. Inside the classical standing wave field, the interaction between atom and the field is position-dependent due to the Rabi frequency of the driving field; hence, as the absorption frequency of the probe field is measured, the position of an atom inside the classical standing wave field will be determined. Localizing of an atom via absorption spectrum occurs during its motion inside the standing wave field. An investigation of the probe field frequency shows that the degree of localization depends on interaction parameters such as detuning, phase difference between applied fields, and Rabi frequency of the driving field.     

Electromagnetically induced transparency in a Zeeman-sublevels Λ-system of cold ~(87)Rb atoms in free space

We report the experimental investigation of electromagnetically induced transparency(EIT) in a Zeeman-sublevelsΛ-type system of cold ~(87)Rb atoms in free space. We use the Zeeman substates of the hyperfine energy states 5~2S_(1/2), F = 2 and 5~2P_(3/2), F = 2 of ~(87)Rb D_2 line to form a Λ-type EIT scheme. The EIT signal is obtained by scanning the probe light over 1 MHz in 4 ms with an 80 MHz arbitrary waveform generator. More than 97% transparency and 100 k Hz EIT window are observed. This EIT scheme is suited for an application of pulsed coherent storage atom clock(Yan B, et al. 2009 Phys.Rev. A 79 063820).     

基于原子的射频识别标签近场散射场矢量测量

基于原子的时间/频率、长度以及磁场、微波电场等方面的量子精密测量近年来引起广泛关注。里德堡原子作为微波精密测量工具,具有可溯源性好、空间分辨率高以及探测灵敏度高等优势。通过室温铯里德堡原子的电磁诱导透明光谱特征分析实现了微波电场矢量空间高分辨测量。利用铯原子蒸气池中共线的耦合光和探测光形成了6S_1/2-6P_3/2-51D_5/2的阶梯型三能级系统,5.365 GHz微波电场将诱导相邻里德堡态51D_5/2-52P_3/2的共振跃迁,导致阶梯型三能级系统的电磁诱导透明光谱发生Autler-Townes分裂。通过计算光谱的分裂间隔可得到可溯源至普朗克常数的微波电场强度,微波电场测量的空间分辨率达到1/31被测微波波长。特别是提出一种新的微波电场极化方向测量方法,解决了基于里德堡原子进行微波电场极化方向测量时无法分辨互补角的问题。通过对射频识别标签的近场散射场进行矢量测量,实现了标签角度的有效识别,角度分辨率达到1.64°,测量结果与有限元分析方法仿真结果吻合地很好。该研究对于微波电场空间高分辨成像、射频识别标签的设计和识别以及电磁兼容测试等方面具有重要价值。     

Motion of an atom under the effect of femtosecond laser pulses: From chaos to spatial localization

The spatial localization of an atom in a field of periodic femtosecond laser pulses is considered. It has been shown that the atom can be localized with absolute accuracy in the nanometer range. The time interval during which the atom is situated in the laser field is only 10^?7–10^?8 of the total localization time interval.