The Rydberg atom-based microwave electric field sensor has high sensitivity for weak RF-field detection. Selection of Rydberg states with larger electric dipole moment is beneficial to enhance the sensitivity, and we choose Rydberg states with its principal quantum number up to n ∼ 80. We study the probe laser transmission response to a microwave field for these chosen high Rydberg states at room temperature. It agrees well with theoretical simulation based on an optical Bloch equation with considered microwave-atom interaction and Doppler broadening effect. In our experiment, the microwave sensing sensitivity based on 85 Rb transition | 78 S 1 / 2 ⟩ → | 78 P 3 / 2 ⟩ arrives at 5.102(49) nV cm − 1 Hz − 1 / 2 at 1 kHz.
The Rydberg atom-based microwave electric field sensor has high sensitivity for weak RF-field detection. Selection of Rydberg states with larger electric dipole moment is beneficial to enhance the sensitivity, and we choose Rydberg states with its principal quantum number up to n ∼ 80. We study the probe laser transmission response to a microwave field for these chosen high Rydberg states at room temperature. It agrees well with theoretical simulation based on an optical Bloch equation with considered microwave-atom interaction and Doppler broadening effect. In our experiment, the microwave sensing sensitivity based on 85 Rb transition | 78 S 1 / 2 ⟩ → | 78 P 3 / 2 ⟩ arrives at 5.102(49) nV cm − 1 Hz − 1 / 2 at 1 kHz.
High-sensitivity amplitude and frequency detection of microwave electric fields is of significant importance in various fields, including communications, microwave quantum technology, aerospace, medicine, and meteorology. Rydberg atom-based sensors promise traceable standards and high sensitivity for detecting weak electric fields and enhancing sensing sensitivity, mainly by using superheterodyne technology and resonant structures. Detecting high-frequency (HF) band fields with high sensitivity using Rydberg atom sensors is a significant challenge due to the requirement of exciting atoms to extremely high energy states for resonant detection. We demonstrate the off-resonant Rydberg atomic superheterodyne architecture with additional resonators for greatly enhancing the sensing sensitivity to HF band fields. In this approach, we propose a miniaturized square spiral resonator with an electrical size of$0.011~\lambda $at 15.54 MHz. To reduce the electric-field-screening effect of the adsorption of alkali metal atoms, we use a monocrystalline sapphire cesium (Cs) vapor cell. By utilizing the off-resonant alternating current (ac) Stark effect, the initial sensitivity of the Rydberg atom sensor without the resonator is measured to be10.39μV/cmHzat room temperature. With the addition of the miniaturized square spiral resonator, the sensitivity significantly improved to2.60nV/cmHz, which has been inaccessible so far with atomic sensors. Here, we provide an enhancement of 72 dB, which is three orders of magnitude improvement in sensitivity than when the resonator is not used. This enhancement resonator extends Rydberg atomic high-sensitivity sensing to the HF band and shows great potential, especially in shortwave radio reception.
We have shown that Rydberg atoms can be used for high-sensitivity, absolute sensing of radio frequency (RF) electric fields. We achieved a sensitivity of 3 μVcm-1Hz-1/2 for two read-out strategies. Results using a Mach-Zehnder interferometer2 and frequency modulated spectroscopy both achieve similar photon shot noise limited sensitivity. Fundamental limits to the sensitivity of the Rydberg atom-based RF electric field sensing have been addressed. Depending on the spectral resolution of the read-out, either the RF induced transmission line frequency splitting, the Autler-Townes regime, or a change in the on-resonant absorption, the amplitude regime, can be used to determine the RF electric field. Here, we present theoretical results of a 3-photon read-out scheme which enables the Autler-Townes regime of Rydberg atom-based RF electrometry to be extended to lower RF electric field strengths. We show that the residual Doppler shifts can, in principle, be reduced to ~11.8 kHz, on the order of the Rydberg atom natural lindewidths, using the approach.
We present a theoretical and experimental investigation of the improvement and determination of the sensitivity of Rydberg atom-based microwave RF sensor. An optical Bloch equation has been set up based on the configuration that two-color cascading lasers exciting atom to highly Rydberg state and a microwave RF coupling this Rydberg state to its adjacent neighbor. The numerical simulation shows that the sensitivity of the atomic RF sensor is correlated with the amplitude strengths of the applied two lasers and the RF itself. It also depends on the frequency detuning of the coupling laser, which induces an asymmetrically optical splitting. The coupling laser frequency fixing at the shoulder of the stronger one is more favorable for a higher sensitivity. Accordingly, we perform an experimental demonstration for the optimization of all these parameters and the sensitivity is improved to 12.50(04) nVcm−1·Hz−1/2.
Atoms form the basis of precise measurement for many quantities (time, acceleration, rotation, magnetic field, etc.). Measurements of microwave frequency electric fields by traditional methods (i.e. engineered antennas) have limited sensitivity and can be difficult to calibrate properly. Highly-excited (Rydberg) neutral atoms have very large electric-dipole moments and many dipole allowed transitions in the range of 1 - 500 GHz. It is possible to sensitively probe the electric field in this range using the combination of two quantum interference phenomena: electromagnetically induced transparency and the Autler-Townes effect. This technique allows for very sensitive field amplitude, polarization, and sub-wavelength imaging measurements. These quantities can be extracted by measuring properties of a probe laser beam as it passes through a warm rubidium vapor cell. Thus far, Rydberg microwave electrometry has relied upon the absorption of the probe laser. We report on our use of polarization rotation, which corresponds to the real part of the susceptibility, for measuring the properties of microwave frequency electric fields. Our simulations show that when a magnetic field is present and directed along the optical propagation direction a polarization rotation signal exists and can be used for microwave electrometry. One central advantage in using the polarization rotation signal rather than the absorption signal is that common mode laser noise is naturally eliminated leading to a potentially dramatic increase in signal-to-noise ratio.
Significant progress has been made in atom-based measurements of length, time, gravity and electromagnetic fields in recently years. Rydberg atom-based microwave electric field measurement, using electromagnetically induced transparency (EIT) in room temperature alkali-metal vapors, has been extensively investigated and aroused the broad interest. This approach may establish a new standard for the measurements of microwave (MW) and radio frequency (RF) electric fields.In this review, we describe the work on a new method of measuring electric fields based on quantum interference by using either cesium or rubidium atoms contained in a dielectric vapor cell. Rydberg atoms with principal quantum number n >>1 have large direct current (DC) polarizabilities and microwave transition dipole moments, thereby making them extremely sensitive to external electric fields. Using the Rydberg three-level EIT to detect the level splitting and shift that is induced by the external field, we can realize a rapid and robust self-calibration method of measuring the electric field in a frequency range from 0.01 GHz to 1000 GHz. For the MW electric field (frequency range > 1 GHz), the MW field causes the Rydberg states to split, known as an Autler-Townes splitting (A-T) effect when the applied microwave can resonate with adjacent Rydberg states. The MW coupled A-T splitting is proportional to the applied electric field strength, from which the field strength is measured. Using the EIT window, a high sensitivity of 3 μV·cm-1·Hz-1/2 and small electric field of 1 μV/cm are expected to be achieved with a modest setup, and the limitations of the sensitivity are also addressed in the review. For the RF field at frequency mj EIT lines, and avoided crossings formed with the fine-structure levels of equal mj and different J's, which is used to calibrate and measure the RF field amplitude. On the other hand, the dependence of the EIT-line strength on the RF field polarization provides a fast and robust polarization measurement of RF fields based on matching experimental data with a theoretical simulation. The measurements of minimum strengths and sensitivity of RF fields based on Rydberg atoms are one order magnitude below the values obtained by traditional antenna methods. The atom-based field measurement paves the way for determining fields through calibration-free, invariable atomic properties and miniaturization. We also propose its various potential applications in the future.
A highly excited Rydberg atom via electromagnetically induced transparency with two color cascading lasers has extreme sensitivity to electric fields of microwave ranging from 100 MHz to over 1 THz. It can be used as susceptible atom-based microwave communication antennas where the carrier wave usually works exactly resonant to the transition between a pair of adjacent Rydberg states with large electric dipole moment. A technique of superheterodyne with a strong on-resonant local microwave oscillator is employed to induce considerable Autler-Townes splitting where the antennas has a highest dynamic response to another weak target signal microwave carrier. To further improve the sensitivity of atomic antenna in communication, we detune the carrier microwave frequency off resonance forming an asymmetrically optical splitting and fix the coupling laser frequency at the shoulder of the stronger one, and optimize the local field strength simultaneously. It gives a sensitivity of 12.50(04) nVcm−1⋅Hz−1/2. Its enhancement mechanism of sensitivity is also proved by a theoretical simulation.