基于Rydberg原子的高灵敏微波探测与通信

利用Rydberg原子作为微波传感器实现了微弱场的测量与通信.在铯原子蒸气池中,相向传输的探测光(852 nm)和耦合光(510 nm)与铯原子相互作用形成阶梯型三能级电磁感应透明光谱,用于实现Rydberg原子的光学探测.频率约为2.19 GHz的强微波场作为本地场(E_L),共振耦合相邻的两个Rydberg能级|68D_5/2>和|69P_3/2>,与具有一定失谐δf的待测微弱信号场(E_s)同时作用于Rydberg原子.Rydberg原子作为微波混频器可直接读出两束微波的差频信号,实现待测信号场的高灵敏探测,对应的最小测量值为E₀=1.7μV/cm,频率分辨率小于1 Hz.在此基础上,对微弱信号场进行编码,实验上很好地还原了加载到微波弱场上的基带信号,测量的传输带宽达200 MHz,实现了微弱场条件下的通信.     

Rydberg原子nS1/2→(n+1)S1/2双光子激发EIT-AT光谱

主要研究了热原子蒸气池中铯Rydberg原子nS_1/2→(n+1)S_1/2微波耦合的双光子光谱.铯原子基态(6S_1/2)、第一激发态(6P_3/2)、Rydberg态(69S_1/2)形成阶梯型三能级系统,弱探测光作用于基态到激发态6S_1/2→6P_3/2的跃迁,强耦合光则作用于6P_3/2→69S_1/2的Rydberg跃迁形成电磁感应透明(EIT)效应,实现对Rydberg原子的光学探测.频率fMW=11.735 GHz的微波场耦合69S_1/2→70S_1/2的Rydberg跃迁,形成微波双光子光谱.利用EIT-AT分裂光谱研究微波电场强度对双光子光谱的影响.研究表明:在强微波场作用时,EIT-AT分裂与微波场功率成正比,而弱微波场时的EIT-AT分裂与微波场功率成非线性依赖关系,理论计算与实验测量结果相一致.本文的研究对微波电场的精密测量具有一定的指导意义.     

Rydberg原子nS1/2→(n+1)S1/2双光子激发EIT-AT光谱

主要研究了热原子蒸气池中铯Rydberg原子nS_1/2→(n+1)S_1/2微波耦合的双光子光谱.铯原子基态(6S_1/2)、第一激发态(6P_3/2)、Rydberg态(69S_1/2)形成阶梯型三能级系统,弱探测光作用于基态到激发态6S_1/2→6P_3/2的跃迁,强耦合光则作用于6P_3/2→69S_1/2的Rydberg跃迁形成电磁感应透明(EIT)效应,实现对Rydberg原子的光学探测.频率fMW=11.735 GHz的微波场耦合69S_1/2→70S_1/2的Rydberg跃迁,形成微波双光子光谱.利用EIT-AT分裂光谱研究微波电场强度对双光子光谱的影响.研究表明:在强微波场作用时,EIT-AT分裂与微波场功率成正比,而弱微波场时的EIT-AT分裂与微波场功率成非线性依赖关系,理论计算与实验测量结果相一致.本文的研究对微波电场的精密测量具有一定的指导意义.     

49S里德堡态的射频双光子光谱

在室温铯原子蒸气池中, 由铯原子基态、激发态和里德堡态构建了阶梯型三能级系统, 研究了里德堡原子阶梯型三能级系统的电磁感应透明(EIT). 在实现电磁感应透明的基础上, 利用16.9 GHz的射频电场耦合相邻的原子里德堡态, 实现49S_1/2→47D_3/2的双光子跃迁, 测量了里德堡原子的射频双光子光谱, 观察到了电磁感应透明光谱的分裂, 进一步研究了电场强度对射频双光子光谱的影响. 利用里德堡原子的EIT效应可实现对射频电场幅值和极化的精密测量, 具有潜在的应用前景.     

弱射频场中Rydberg原子的电磁感应透明

在铯原子室温蒸气池中研究了弱射频场中Rydberg原子阶梯型三能级系统的电磁感应透明(EIT)效应.铯原子基态6S_(1/2)、第一激发态6P_(3/2)和Rydberg 48D_(5/2)态形成阶梯型三能级系统,探测光共振作用于6S_(1/2)(F=4)→6P_(3/2)(F′=5)的跃迁,耦合光在Rydberg跃迁线6P_(3/2)(F′=5)→48D_(5/2)附近扫描,形成Rydberg原子EIT.当对铯原子施加一个80 MHz的弱射频电场时,48D_(5/2)Rydberg原子的EIT光谱发生Stark频移和分裂,同时产生由射频场调制Rydberg能级的偶数级边带,测量结果与Floquet理论模拟的结果相符合.同时,改变弱射频电场的频率研究了铯Rydberg能级的自电离效应对Rydberg原子Stark谱的影响,据此,我们提出将电极板置于铯原子蒸气池内的方案以减少自电离效应的影响.在弱射频Stark谱中,mj=5/2的Stark谱与mj=1/2,3/2的二级边带形成多个能级交叉,这些能级交叉点提供了一种基于原子的精确校准射频电场的新方法.     

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.     

基于Rydberg原子的超宽频带射频传感器

Rydberg原子具有极大的极化率和微波跃迁偶极矩,对外界电磁场非常敏感,可实现基于Rydberg原子的超宽频带射频电场的高分辨高灵敏测量.通过Rydberg原子的全光学无损的电磁感应透明探测手段,可以实现基于原子的快速免校准宽频带(0.01-1000 GHz)外电场的精密测量.对于频率大于1 GHz的微波场,由微波场耦合相邻Rydberg能级形成的Autler-Townes分裂进行测量;而对于频率小于1 GHz的长波射频场,由Rydberg能级的射频边带能级进行测量.这种方法是基于原子能级参数,可溯源到基本物理常量,不依赖于外界参考;且对电场无干扰,易于实现微型化和集成化,具有广泛的应用前景.本文主要综述了基于Rydberg原子的外电场测量的最新研究进展,重点介绍长波长射频场的测量,包括电场强度、频率以及极化方向的测量,详细介绍了其测量原理和探测灵敏度,并讨论了其应用前景及未来发展方向.     

Resonant enhancement of dielectronic recombination by a microwave field

We have observed dielectronic recombination of Ba+ and e(-) from a continuum of finite bandwidth in the presence of microwave fields of frequencies 8.08 and 12.05 GHz and amplitudes of up to 2 V/cm. There are sharp resonant enhancements when the microwave frequency matches the Deltan = 1, 2, and 3 resonances of the intermediate autoionizing Rydberg states, and we attribute the enhancements to resonant microwave Stark l mixing. The microwave field provides a simple and powerful way to enhance the recombination rate for incident electrons of a specific energy.     

基于量子相干效应的无芯射频识别标签的空间散射场测量

基于原子蒸汽池中铯里德伯原子的电磁感应透明光谱在微波场作用下的Aulter-Towns效应,测量了无芯射频识别标签线形散射单元的近场散射微波电场二维空间分布,空间分辨率可达到亚微波波长.实现了射频电场极化方向与线形散射体标签夹角的有效分辨.电磁仿真软件的仿真结果与实验测量符合得很好.本研究提供了一种测量微波电场近场测量的新方法,对无芯射频识别标签的散射单元设计和标定以及电子电路的电磁辐射测量具有重要的意义.     

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。     

微波驱动精细结构能级跃迁引起的电磁诱导负折射效应

本文通过建立Λ形四能级原子系统, 研究了微波驱动精细结构能级跃迁引起的电磁诱导负折射效应. 微波场作用于基态精细结构能级之间, 与不同精细结构能级之间的电偶极矩或磁偶极矩发生耦合, 使系统在某些频率处呈现负折射特性.同时, 两个耦合场各自激励一对基态和激发态之间的光学跃迁. 通过改变两个耦合场的频率失谐量控制负折射区域的频带宽度.结果表明, 耦合场失谐时出现负折射特性的频率范围比耦合场共振时迅速缩小, 而且耦合场负失谐和正失谐时的变化规律不同.     

Interaction-enhanced double resonance in cold gases

A new type of double-resonance spectroscopy of a quantum gas based on interaction-induced frequency modulation of a probe transition has been considered. Interstate interaction of multilevel atoms causes a coherence-dependent collisional shift of the transition between the atomic states |1〉 and |2〉 due to a nonzero population of the state |3〉. Thus, the frequency of the probe transition |1〉?|2〉 experiences oscillations associated with the Rabi oscillations between the states |1〉 and |3〉 under continuous excitation of the drive resonance |1〉?|3〉. Such a dynamic frequency shift leads to a change in the electromagnetic absorption at the probe frequency and, consequently, greatly enhances the sensitivity of double-resonance spectroscopy as compared to traditional “hole burning”, which is solely due to a decrease in the population of the initial state |1〉. In particular, it has been shown that the resonance linewidth is determined by the magnitude of the contact shift and the amplitude of the drive field and does not depend on the static field gradient. The calculated line shape and width agree with the low-temperature electron-nuclear double-resonance spectra of two-dimensional atomic hydrogen.     

Rydberg quantum computation with nuclear spins in two-electron neutral atoms

Alkaline-earth-like (AEL) atoms with two valence electrons and a nonzero nuclear spin can be excited to Rydberg state for quantum computing. Typical AEL ground states possess no hyperfine splitting, but unfortunately a GHz-scale splitting seems necessary for Rydberg excitation. Though strong magnetic fields can induce a GHz-scale splitting, weak fields are desirable to avoid noise in experiments. Here, we provide two solutions to this outstanding challenge with realistic data of well-studied AEL isotopes. In the first theory, the two nuclear spin qubit states |0〉 and |1〉 are excited to Rydberg states |r〉 with detuning Δ and 0, respectively, where a MHz-scale detuning Δ arises from a weak magnetic field on the order of 1 G. With a proper ratio between Δ and Ω, the qubit state |1〉 can be fully excited to the Rydberg state while |0〉 remains there. In the second theory, we show that by choosing appropriate intermediate states a two-photon Rydberg excitation can proceed with only one nuclear spin qubit state. The second theory is applicable whatever the magnitude of the magnetic field is. These theories bring a versatile means for quantum computation by combining the broad applicability of Rydberg blockade and the incomparable advantages of nuclear-spin quantum memory in two-electron neutral atoms.     

Dynamics mechanism of optical-optical double-resonant multiphoton ionization of nitrogen dioxide

The optical-optical double-resonant multiphoton ionization (OODR-MPI) spectrum of NO2 molecule in the 460-605-nm wavelength region of the probe photon is presented. The mechanism of the OODR-MPI of NO2 molecule is analyzed. The results show that the resonant features can be assigned to the transitions from the first 3sσg Rydberg intermediate resonant state to the final npσu Rydberg series. The ionization pathway is NO2 (X2A1) 3hv1→ 3sσghv2→npσu hv2 or autoionization→NO2+ + e. It is found that the converging potential of the npσu Rydberg series and the quantum defect of np orbit about NO2 are (78803 ± 14) cm-1 and 0.652 ± 0.014, respectively. The bending vibration frequency of 5pσu state is determined also.     

锶原子互组跃迁荧光探测系统的研制

锶原子单态和三重态间的互组跃迁(5s2)1S0-(5s5p)3P1辐射率远小于一般的电偶极跃迁,共振跃迁荧光信号微弱。介绍了一种应用于探测该互组跃迁荧光谱的直流偏置探测器。该探测器选用极低输入偏置电流运算放大器作为前置放大,具有信噪比高、增益高、偏置可调等优点。此探测器探测增益为106 V/W量级,-3dB带宽为1MHz。实验中利用该探测器对锶原子互组跃迁(5s2)1S0-(5s5p)3P1微弱共振荧光进行探测,获得信噪比很好的共振荧光谱,且无直流偏置,并由此获得高信噪比的鉴频曲线。应用该探测器观测到了饱和荧光谱线以及对应的鉴频曲线,可用于689nm激光锁频,应用于锶光钟系统。     

调制激光场中Rydberg原子的电磁感应透明

本文主要研究了调制探测激光场中铯Rydberg 原子阶梯型三能级系统的电磁感应透明(EIT) 效应. 铯原子基态6S_1/2, 第一激发态6P_3/2 和Rydberg 态形成阶梯型三能级系统, 探测光作用于6S_1/2 (F = 4)→6P_3/2(F' = 5) 的跃迁, 耦合光在Rydberg 跃迁线6P_3/2→49S_1/2 附近扫描, 形成Rydberg 原子EIT. 当对探测光频率施加一个几kHz 的调制时, 调制解调后的EIT 信号分裂为两个峰, 双峰间距与调制频率无关,而与调制幅度导致的失谐量大小(频率调制幅度) 成正比, 双峰间隔的一半等于探测光频率调制幅度的λ_p/λ_c = 1.67 倍. 实验结果与理论计算相一致. 本文的研究结果可应用于激光线型和频率抖动的实时监测.     

一价镧离子高n里德伯态

基于五步激光共振激发,经由中间态(Xe) 5d6d~3F_2的一价镧离子光谱,分析了该实验谱,确定了一价镧离子一强一弱两个自电离里德伯系列.同时利用多通道量子亏损理论(MQDT)框架下的相对论多通道理论(RMCT)计算,标识了这两个自电离里德伯系列,强的自电离里德伯系列标识为5dnp(5/2,1/2)_3和/或5dnp(5/2,1/2)_2,弱系列标识为为5dnf(5/2,5/2)_3和/或5dnf(5/2,5/2)_2.根据实验谱峰数据,发现有效量子数很高时,里德伯和自电离里德伯能级量子数亏损随激发能量不平滑变化,并分析了可能的原因.     

A multi-band atomic candle with microwave-dressed Rydberg atoms

Stabilizing important physical quantities to atom-based standards lies at the heart of modern atomic, molecular and optical physics, and is widely applied to the field of precision metrology. Of particular importance is the atom-based microwave field amplitude stabilizer, the so-called atomic candle. Previous atomic candles are realized with atoms in their ground state, and hence suffer from the lack of frequency band tunability and small stabilization bandwidth, severely limiting their development and potential applications. To tackle these limitations, we employ microwave-dressed Rydberg atoms to realize a novel atomic candle that features multi-band frequency tunability and large stabilization bandwidth. We demonstrate amplitude stabilization of microwave field from C-band to Ka-band, which could be extended to quasi-DC and terahertz fields by exploring abundant Rydberg levels. Our atomic candle achieves stabilization bandwidth of 100 Hz, outperforming previous ones by more than two orders of magnitude. Our simulation indicates the stabilization bandwidth can be further increased up to 100 kHz. Our work paves a route to develop novel electric field control and applications with a noise-resilient, miniaturized, sensitive and broadband atomic candle.     

Enhancement of Rydberg atom interactions using ac Stark shifts

The ac Stark effect was used to induce resonant energy transfer between translationally cold 85Rb Rydberg atoms. When a 28.5 GHz dressing field was set at specific field strengths, the two-atom dipole-dipole process 43d5/2+43d5/2-->45p3/2+41f was dramatically enhanced, due to induced degeneracy of the initial and final states. This method for enhancing interactions is complementary to dc electric-field-induced resonant energy transfer, but has more flexibility due to the possibility of varying the applied frequency.     

Analysis of a teleportation scheme involving cavity field states in a linear superposition of Fock states

We analyse a teleportation scheme of cavity field states. The experimental sketch discussed makes use of cavity quantum electrodynamics involving the interaction of Rydberg atoms with superconducting (micromaser) cavities as well as with classical microwave (Ramsey) cavities. In our scheme the Ramsey cavities and the atoms play the role of auxiliary systems used to teleport a field state, which is formed by a linear superposition of vacuum |∅〉 and the one-photon state |1〉, from a micromaser cavity to another.