Atom Based Vector Microwave Electrometry Using Rubidium Rydberg Atoms in a Vapor Cell

Abstract

It is clearly important to pursue atomic standards for quantities like electromagnetic fields, time, length and gravity. We have recently shown, using Rydberg states, that Rb atoms in a vapor cell can serve as a practical, compact standard for microwave electric field strength. Here, we demonstrate, for the first time, that Rb atoms excited in a vapor cell can also be used for vector microwave electrometry by using Rydberg atom electromagnetically induced transparency. We describe the measurements necessary to obtain an arbitrary microwave electric field polarization at a resolution of 0.5• . The experiments are compared to theory and found to be in excellent agreement.PACS numbers: 32.80. Rm, 42.62.Fi, 03.50.De, 07.50.Ls Quantum systems, such as atoms, have already been adopted as time and length standards because they offer significant advantages for making stable and uniform measurements of these quantities [1,2]. Atoms have also been successfully used for magnetometry, reaching impressive sensitivity and spatial resolutions [3][4][5][6][7][8]. Despite these successes, it is only recently that atoms have been used for practical microwave (MW) electrometry and achieved sensitivities below current standards by exploiting the properties of Rydberg atoms [9]. Rydberg atoms have been used for electrometry for some time, but almost exclusively in elaborate laboratory setups [10][11][12][13][14][15][16][17][18][19][20][21].The relative lag of atom based electrometry compared to magnetometry is not simply due to a lack of importance. The accurate measurement of MW electric field strength and polarization offers interesting possibilities for antenna calibration and MW electronics development, as well as for realizing an atomic candle for MW electric field stabilization [22,23], to name a few important examples. Atom based MW electrometry, therefore, has the potential to lead to revolutionary advances in the development of MW electronics, advanced radar applications, and materials used in MW systems. So far, only the magnetic field has been accessible in the near-field MW regime [24,25] and our method can be valuable for measuring MW electric fields in the near-field. Recall, there is not generally a straightforward relation between the MW magnetic and electric fields in the near-field.In this paper, we demonstrate a scheme for vector MW electrometry using Rydberg atom electromagnetically induced transparency (EIT) [26,27] in Rb atomic vapor cells. We achieve an angular resolution of 0.5• and show the method can be realized by comparing experimental data to theory. The agreement between theory and experiment is shown to be excellent. The vector measurements here are compatible with our prior work where we attained a minimum detectable electric field amplitude of ∼ 8 µV cm [9]. To date, EIT has been principly used for vector magnetometry [28,29]. To measure the strength and polarization of a MW electric field, we use the Rb level system shown in Figure 1a. In the 3-level system, 5S 1/2 − 5P 3/2 − 53D 5/2 , quantum in...