Ac Stark Effect Research Articles

Study of coherent population trapping and AC Stark effect in ensembles of NV-centers in diamond at room temperature in microwave range

We study coherent population trapping and AC Stark effect using microwave transitions between the sublevels of the ground state of the NV-center. Sublevels with different projections of the nuclear spin of the nitrogen atom are used to implement the -scheme. Dependence of the characteristics of the coherent population trapping dip on the control field frequency and intensity is studied. Various schemes for observing the AC Stark effect are considered. Keywords: NV-center, coherent population trapping, AC Stark.

Исследование когерентного пленения населенности и динамического эффекта Штарка в ансамблях NV-центров в алмазе при комнатной температуре в микроволновом диапазоне

We study coherent population trapping and AC Stark effect using microwave transitions between the sublevels of the ground state of the NV-center. Sublevels with different projections of the nuclear spin of the nitrogen atom are used to implement the Lambda-scheme. Dependence of the characteristics of the coherent population trapping dip on the control field frequency and intensity is studied. Various schemes for observing the AC Stark effect are considered.

Measurement of microwave electric field based on electromagnetically induced transparency by using cold Rydberg atoms

Microwave electric fields are measured by using cold Rydberg atoms. We obtain spindle-shaped cold atomic clouds in a magneto-optical trap and then pump the cold atoms to quantum state 5S<sub>1/2</sub>, <i>F</i> = 2, <i>m</i><sub>F</sub> = 2 by using an optical-pump laser. We obtain the Rydberg electromagnetic induction transparency (EIT) spectrum peak with narrow linewidth by the low temperature and small residual Doppler broadening. The results show that the typical EIT linewidth with 16 μK cold atoms is about 460 kHz which is 15 times narrower than that of 7 MHz obtained in the thermal vapor cell. The microwave electric field amplitude is measured by Autler-Townes splitting (EIT-AT splitting) in the cold atoms at frequencies of 9.2, 14.2 and 22.1 GHz, receptively. The results show that there is a good linear relationship between the EIT-AT splitting interval and the microwave electric field amplitude. The lower limit of the microwave electric field amplitude that can be measured in the linear region can reach as low as 222 μV/cm, which is about 22 times larger than the lower limit in the traditional thermal vapor cell about of 5 mV/cm. The improvement of the lower limit by EIT-AT splitting method is roughly proportional to the narrowing EIT line width by cold atom samples. This demonstrates that benefiting from the smaller residual Doppler effect and the narrower EIT linewidth in cold atoms, the cold atom system is more advantageous in the experimental measuring of the weak microwave electric field amplitude by using the EIT-AT splitting method. This is of great benefit to the absolute calibration of very weak microwave electric fields. Furthermore, the lower limit of the microwave electric field amplitude that can be measured is smaller than 1 μV/cm by using the change of transmittance of the prober laser at the EIT resonance, and the corresponding sensitivity can reach 1 μV·cm<sup>–1</sup>·Hz<sup>–1/2</sup>. These results demonstrate the advantages of cold atomic sample in microwave electric field measurement and its absolute calibration.

Observation of Aulter–Townes splitting in subwavelength grating metamaterial ring resonators

Subwavelength grating metamaterial (SGM) waveguide is typically treated as a homogeneous medium without considering intra-waveguide reflection. However, this approximation is not always valid, especially in resonators. In this paper, we show that the reflection-induced mutual coupling between the clock-wise and counter-clock-wise resonant modes in a subwavelength grating metamaterial waveguide ring resonator (SGMRR) breaks the degeneracy of the two modes, leading to the formation of Autler–Townes splitting. This phenomenon could be leveraged to improve the detection limit of SGMRR-based sensors.

Discerning the transition from electromagnetically induced transparency to Autler–Townes splitting using the decaying dressed state formalism

We use biorthogonal basis consisting of the ‘right’ and ‘left’ eigenvectors of the effective non-Hermitian Hamiltonian of a three-level system driven by a bi-chromatic field, and resolve the probe absorption spectrum into components corresponding to the decaying dressed states of the system. It is observed that the spectrum primarily consists of three components and two of them undergo dramatic changes when the control field Rabi frequency is changed from the low to high field regime. Based on the symmetry properties of a combination of these components, a parameter internal to the dynamics of the system is defined and is used to distinguish between electromagnetically induced transparency (EIT) and Autler–Townes (AT) splitting, and the threshold for transition between them in an objective manner. The formulation is further extended to the resonance fluorescence spectrum on the probe transition in the EIT and AT regimes.

New cross-coupled resonator induced shifted absorption (CRISA) in double microring resonators using a cross-coupling-structure technique

We report, for the first time to the best of our knowledge, a technique that employs ′cross-coupling structure’ in the cascaded microring resonators (MRRs) to bring new optical analogues of quantum coherence phenomena. The new configuration resembles a standard double resonator (SDR) but uses cross-coupled–based directional couplers (DCs) instead of the typical direct-coupled–based DCs. One of its unique features is that it does not exhibit the typical SDR’s signature quantum coherence analogue effects like coupled-resonator induced transparency (CRIT) or coupled-resonator induced absorption (CRIA). On the contrary, it produces a new very narrow reflection dip positioned at single-pass phase shift θ = − π/2 which we refer to as cross-coupled resonator induced shifted absorption (CRISA). We compare extensively CRISA’s characteristics with the CRIT, CRIA, and Autler-Townes splitting (ATS) found in SDR. The technique opens up new configurations with richer optical behaviours that could find potentially still unexplored applications.

Analytical investigation on the Autler–Townes splittings and the two-photon effects in a Doppler free signal lineshape of a double-$$\varvec{\lambda }$$ type four-level system

Analytical investigation on the Autler–Townes splittings and the two-photon effects in a Doppler free signal lineshape of a double-$$\varvec{\lambda }$$ type four-level system

Transfer of Orbital Angular Momentum of Light Using Autler-Townes Splitting

We propose a scheme to exchange optical vortices beyond electromagnetically induced transparency (EIT) but based on four-wave mixing (FWM) in a five-level atomic system consisting of two Λ subsystems linked via a weak driving field. When the laser fields are strong enough, the quantum interference responsible for the EIT in each Λ subsystem is washed out, giving rise to the Autler-Townes splitting (ATS). When only one of the control fields carries an optical vortex, it is shown that the generated FWM field obtains the vorticity of the vortex control. We distinguish between three different regimes, i.e., a pure EIT, a joint EIT-ATS, and a dual-ATS, where the optical angular momentum (OAM) translation can take place. Elaborating on the distinction between three regimes through numerical analysis, we find that the maximum energy conversion efficiency is obtained in the joint EIT-ATS and dual-ATS regimes. The latter is more favorable as the absorption losses vanish as the beam propagates into the atomic cloud. The results may find applications in the implementation of high-efficient frequency and OAM conversion devices for quantum information processing.

Parity-pair-mixing effects in nonlinear spectroscopy of HDO.

A non-linear spectroscopic study of the HDO molecule is performed in the wavelength range of 1.36-1.42 μm using noise-immune cavity-enhanced optical-heterodyne molecular spectroscopy (NICE-OHMS). More than 100 rovibrational Lamb dips are recorded, with an experimental precision of 2-20 kHz, related to the first overtone of the O-H stretch fundamental of HD16O and HD18O. Significant perturbations, including distortions, shifts, and splittings, have been observed for a number of Lamb dips. These spectral perturbations are traced back to an AC-Stark effect, arising due to the strong laser field applied in all saturation-spectroscopy experiments. The AC-Stark effect mixes parity pairs, that is pairs of rovibrational states whose assignment differs solely in the Kc quantum number, where Kc is part of the standard J K a,K c asymmetric-top rotational label. Parity-pair mixing seems to be especially large for parity pairs with Ka ≥ 3, whereby their energy splittings become as small as a few MHz, resulting in multi-component asymmetric Lamb-dip profiles of gradually increasing complexity. These complex profiles often include crossover resonances. This effect is well known in saturation spectroscopy, but has not been reported in combination with parity-pair mixing. Parity-pair mixing is not seen in H2 16O and H2 18O, because their parity pairs correspond to ortho and para nuclear-spin isomers, whose interaction is prohibited. Despite the frequency shifts observed for HD16O and HD18O, the absolute accuracy of the detected transitions still exceeds that achievable by Doppler-limited techniques.

Dynamics of superconducting qubit relaxation times

Superconducting qubits are a leading candidate for quantum computing but display temporal fluctuations in their energy relaxation times T1. This introduces instabilities in multi-qubit device performance. Furthermore, autocorrelation in these time fluctuations introduces challenges for obtaining representative measures of T1 for process optimization and device screening. These T1 fluctuations are often attributed to time varying coupling of the qubit to defects, putative two level systems (TLSs). In this work, we develop a technique to probe the spectral and temporal dynamics of T1 in single junction transmons by repeated T1 measurements in the frequency vicinity of the bare qubit transition, via the AC-Stark effect. Across 10 qubits, we observe strong correlations between the mean T1 averaged over approximately nine months and a snapshot of an equally weighted T1 average over the Stark shifted frequency range. These observations are suggestive of an ergodic-like spectral diffusion of TLSs dominating T1, and offer a promising path to more rapid T1 characterization for device screening and process optimization.

Slowing down light in a qubit metamaterial

The rapid progress in quantum information processing leads to a rising demand for devices to control the propagation of electromagnetic wave pulses and to ultimately realize universal and efficient quantum memory. While in recent years, significant progress has been made to realize slow light and quantum memories with atoms at optical frequencies, superconducting circuits in the microwave domain still lack such devices. Here, we demonstrate slowing down electromagnetic waves in a superconducting metamaterial composed of eight qubits coupled to a common waveguide, forming a waveguide quantum electrodynamics system. We analyze two complementary approaches, one relying on dressed states of the Autler–Townes splitting and the other based on a tailored dispersion profile using the qubits tunability. Our time-resolved experiments show reduced group velocities of down to a factor of about 1500 smaller than in vacuum. Depending on the method used, the speed of light can be controlled with an additional microwave tone or an effective qubit detuning. Our findings demonstrate high flexibility of superconducting circuits to realize custom band structures and open the door to microwave dispersion engineering in the quantum regime.

Observation of oscillatory Raman gain associated with two-photon Rabi oscillations of nanofiber-coupled atoms

Quantum emitters with a Λ-type level structure enable numerous protocols and applications in quantum science and technology. Understanding and controlling their dynamics is, therefore, one of the central research topics in quantum optics. Here, we drive two-photon Rabi oscillations between the two ground states of cesium atoms and observe the associated oscillatory Raman gain and absorption that stems from the atom-mediated coherent photon exchange between the two drive fields. The atoms are efficiently and homogeneously coupled with the probe field by means of a nanofiber-based optical interface. We study the dependence of the two-photon Rabi frequency on the system parameters and observe Autler–Townes splitting in the probe transmission spectrum. Beyond shedding light on the fundamental processes underlying two-photon Rabi oscillations, our method could also be used to investigate (quantum) correlations between the two drive fields as well as the dynamical establishment of electromagnetically induced transparency.

High-fidelity quantum control via Autler-Townes splitting

We propose quantum control protocols for the high-fidelity preparation of target states in systems with Autler-Townes splitting. We investigate an approximated three-level system obtained from a four-level one by adiabatically eliminating a state that does not participate in the evolution. In our work we use linear, arctan, and Roland-Cerf functions for transferring population between two eigenstates of the system obtaining a high fidelity for long evolution times. Additionally, in order to overcome the restriction given by the lifetimes of the experimental setup, we propose an accelerated adiabatic evolution with a shortcut to adiabaticity protocol, which allows us to reach fidelities close to one but much faster.

Friedrich-Wintgen bound states in the continuum and induced resonances in a loop laterally coupled to a waveguide

The concept of bound states in the continuum (BICs) in a simple cavity attracts much interest in recent works in wave physics. The BICs are perfectly confined modes with an infinite lifetime that reside inside the continuous spectrum of radiative modes, but they remain totally decoupled from it. There exist several types of BICs based on their physical origin: one of the most interesting types is Friedrich-Wintgen (FW) BICs which result from the destructive interference of two resonant modes belonging to the same cavity. Here, we investigate theoretically and experimentally the existence of FW BICs in a side-coupled loop. The cavity is made of a loop of length $2d={d}_{2}+{d}_{3}$ connected to a stub of length ${d}_{4}$. The whole cavity is attached vertically to two semi-infinite waveguides by a wire of length ${d}_{1}$. We demonstrate that the BICs can be induced either by the loop-stub system or by the two arms of lengths ${d}_{2}$ and ${d}_{3}$ of the loop for specific geometrical parameters. When a perturbation in the system produces a deviation from the BIC condition, the latter transforms to either electromagnetically induced transparency (EIT) or reflection (EIR) or Autler-Townes splitting (ATS) resonances. Both EIT and ATS exhibit similar features in the transmission spectrum, namely, a transparency window; however, they have different physical origins. Therefore, EIT and ATS resonances are fitted with corresponding analytical model expressions, revealing good agreements. The Akaike's information criterion is then used to quantitatively discern EIT from ATS and the transition from ATS to EIT is also carried out. Our theoretical results are obtained by means of the Green's function method which enables us to obtain the transmission and reflection coefficients, dispersion relations, as well as density of states and scattering matrix. An experimental validation of all these results is performed in the radio-frequency domain using coaxial cables.

Generation of tripartite squeezed state by cascaded four-wave mixing in single hot rubidium atomic system

We report the quantum correlated triple beams via cascaded four-wave mixing (CFWM) amplified in single hot atomic vapor. Experimentally, we show that strong quantum correlation of three light beams, among them any two’s quantum correlation is characterized by the maximum value of intensity-difference squeezing (IDS) about −7.8 ± 0.3 dB. We found there is IDS between two idler beams, because two pairs of Einstein–Podolsky–Rosen injections potentially exist in our system. Besides, CFWM can emit three-mode beams at three different frequencies, in which these beams can be well separated in the spatial domain. Moreover, much difference with other methods, the injecting probe field can manipulate the gain and IDS of output three-mode light beams, which is resulting from competition relationship between cascaded two four-wave mixing processes. More interestingly, Autler–Townes splitting of gain peaks of output signals due to dressing effect of pumping fields, will lead to the evolution of measured two- and three-mode IDS from single-mode to multi-mode at frequency domain. This result will provide a multimode quantum resource which can potentially realize multimode entanglement and quantum networks.

Distinguishing electromagnetically induced transparency and Autler–Townes splitting effects in photonic crystal nanobeam-waveguide coupled system by AIC

In this paper, we quantitatively distinguish electromagnetically induced transparency (EIT) and Autler–Townes splitting (ATS) in a photonic crystal nanobeam cavity (PCNC)-waveguide coupled system. Akaike’s information criterion (AIC) is applied to calculate the two effects’ respective weights in the simulated transmission spectra. EIT and ATS are two phenomena that both have a transparent window in the transmission caused by different mechanisms in the atomic system. It’s difficult to distinguish these two phenomena directly from the spectrum. AIC provides a measurement distinguishing the two effects in the atomic, plasmonic, optomechanical system, etc. Based on the temporal coupled-mode theory, the theoretical model of the structure is established, and the transmission formula is deduced. Distance between the PCNC and the waveguide is varied to further explore the factors affecting the weights. The study shows great potential in precisely and quantitatively evaluating the interference of fields in future optical on-chip integration design.

Phase dependent of electromagnetically induced grating in a quantum system

In this letter, we theoretical investigated electromagnetically induced phase grating in a three-level quantum system. The quantum system interacts with two weak probe and signal lights and a strong coupling light. We show that in two different parametric conditions i.e. in electromagnetically induced transparency (EIT) and Autler–Townes splitting (ATS) regimes, the probe and signal beams can be diffracted into the high-order directions. We realized that in the EIT regime, some of probe energy transfer from zero order to the high orders, while in ATS regime most of probe energy transfers to the high orders and small portion remain in the zero order.

Improvement of microwave detection sensitivity with atoms based on cavity enhancement effect

A high-precision microwave detection technology using atoms is an essential foundation in future communication technologies. In this study, improvement of microwave detection sensitivity by atoms is realized. First, an open-loop resonator is designed based on finite element simulation and subsequently fabricated; then, the microwave electric field intensity is measured with and without the resonator, based on the electromagnetically induced transparency Autler–Townes effect. The microwave electric field with different input power is measured, and the improvement achieved with the resonator is verified. The optimal detection sensitivity is improved from 2.14(5) to 0.73(4)V m−1, and the sensitivity is improved by a factor of approximately 2.9. These results provide a practical reference for the application of high-precision detection of microwave electric fields with atoms and atomic microwave communication in the future.

Measurements of Dipole Moments for the 5s5p 3 P 1–5sns 3 S 1 Transitions via Autler-Townes Spectroscopy

We report on experimental measurements of the transition dipole moments (TDMs) between the intermediate state 5s5p 3 P 1 and the triplet Rydberg series 5sns 3 S 1 in an ultracold strontium gas. Here n is the principal quantum number ranging from 19 to 40. The transition 5s5p 3 P 1–5sns 3 S 1 is coupled via an ultraviolet (UV) beam, inducing Autler–Townes splitting of both states. Such a splitting of the intermediate state is spectroscopically measured by using absorption imaging on a narrow transition 5s 2 1 S 0–5s5p 3 P 1 in an ultracold gas of strontium atoms. The power and size of the UV beam are carefully determined, with which the TDMs are extracted from the measured Autler–Townes splitting. The experimentally obtained TDMs are compared to the calculations based on a parametric core potential, on a Coulomb potential with quantum defect, and on the open-source library Alkali Ryderg calculator, finding good agreement with the former two models and significant deviation with the latter.

Measurement of dc and ac Electric Fields inside an Atomic Vapor Cell with Wall-Integrated Electrodes

We present and characterize a Rb atomic vapor cell with silicon-ring electrodes embedded between borosilicate glass tubes. The ring electrodes can be externally connectorized for application of electric fields to the inside of the cell. An atom-based, all-optical, laser-spectroscopic field-sensing method is employed to measure electric fields in the cell. Here, the Stark effect of electric-field-sensitive rubidium Rydberg atoms is exploited to measure dc electric fields in the cell of approximately $5$ V/cm, with a relative uncertainty of 10%. Measurement results are compared with dc field calculations, allowing us to quantify electric field attenuation due to free surface charges inside the cell. We further measure the propagation of microwave fields into the cell, using Autler-Townes splitting of Rydberg levels as a field probe. Results are obtained for a range of microwave powers and polarization angles relative to the cell's ring electrodes. We compare the results with microwave-field calculations.