We present an electrically-small Rydberg atom electric field sensor with the ability to extract the three-dimensional $k$-vector of an elliptically polarized radio frequency (rf) field. In most mediums, the $k$-vector (or wave vector) provides the direction of propagation of an electromagnetic wave. Our method uses a field vector measurement at a single point in space and is thus compatible with a sensor volume that is arbitrarily small compared to the carrier wavelength. We measure the $k$-vector of a circularly polarized signal field with average absolute errors in the polar and azimuthal angles of $33~\text{mrad}$ and $43~\text{mrad}$ respectively, and statistical noise of $1.3~\text{mrad}/\sqrt{\text{Hz}}$ and $1.5~\text{mrad}/\sqrt{\text{Hz}}$. Additionally, we characterize the performance of the sensor as a function of the ellipticity of the input field and the size of the sensing region. We find that the sensor works over a broad range of ellipticities and validate that an electrically-small sensing region is optimal.
Determination of quantum defect for the Rydberg P series of Ca II
在射频离子阱中对激光冷却的$^{40}$ Ca $^+$离子的里德堡23 P $_{1/2}$态进行了实验研究。使用微动边带光谱上的一个狭窄的四极跃迁，振荡电场在离子位置的精确特征，和调制的里德伯跃迁由于这个字段被最小化。通过对这条P线和先前测量的Ca II的P和F能级能量的相关拟合，我们确定了95 751.916（32）$\rm {cm}^{-1}$的电离能，与公认的值一致，以及$n$ P $_{1/2}$态的量子亏损。
Proposal for the determination of nuclear masses by high-precision spectroscopy of Rydberg states
单电子离子里德伯态的理论处理由于实际上没有核尺寸修正而变得容易，而像里德伯常量这样的基本常数可能在计划中的高精度光谱实验的范围内。因此，在里德伯态之间转移跃迁能量的主要核效应是由于核质量。因此，里德伯跃迁的光谱测量可以用来精确地推断核质量。详细探讨了这种方法在氢和氘以及类氢锂和碳中的可能应用。为了完成主量子数n=5，..态的量子电动力学（QED）自能余项函数的分析、数值和解析计算，8和角动量L=n-1和L=n-2（j = L +/- 1/2）。
Angle-of-Arrival Determination of Radio-Frequency Fields Using Stark-Shifted Rydberg-EIT Spectra
National Institute of Standards and Technology（美国国家标准与技术研究院）；Department of Electrical, Computer, and Energy Engineering, University of Colorado, Boulder（科罗拉多大学博尔德分校电气、计算机与能源工程系）
Three-dimensional three-photon Stark spectroscopy of a single Rb Rydberg atom in an ultrahigh-vacuum glass cell with eight electrodes
Rzhanov Institute of Semiconductor Physics SB RAS（列扎诺夫半导体物理研究所西伯利亚分院）；Novosibirsk State University（新西伯利亚国立大学）；Institute of Laser Physics SB RAS（激光物理研究所西伯利亚分院）
Measurement of the $\text{1}^\text{3}\text{S}_\text{1} \to \text{2}^\text{3}\text{S}_\text{1}$ interval in positronium using field-ionization of Rydberg states
