Electromagnetically Induced Transparency Research Articles

All-optical quantum information processing via a single-step Rydberg blockade gate.

One of the critical elements in the realization of the quantum internet are deterministic two-photon gates. This CZ photonic gate also completes a set of universal gates for all-optical quantum information processing. This article discusses an approach to realize a high fidelity CZ photonic gate by storing both control and target photons within an atomic ensemble using non-Rydberg electromagnetically induced transparency (EIT) followed by a fast, single-step Rydberg excitation with global lasers. The proposed scheme operates by relative intensity modulation of two lasers used in Rydberg excitation. Circumventing the conventional π-gap-π schemes, the proposed operation features continuous laser protection of the Rydberg atoms from the environment noise. The complete spatial overlap of stored photons inside the blockade radius optimizes the optical depth and simplifies the experiment. The coherent operation here is performed in the region that was dissipative in the previous Rydberg EIT schemes. Encountering the main imperfection sources, i.e., the spontaneous emission of the Rydberg and intermediate levels, population rotation errors, Doppler broadening of the transition lines, storage/retrieval efficiency, and atomic thermal motion induced decoherence, this article concludes that with realistic experimental parameters 99.7% fidelity is achievable.

Generation and Controllability of High-Dimensional Rogue Waves in an Electromagnetically Induced Transparent Medium

We propose a scheme to generate and control high-dimensional rogue waves in a coherent three-level Λ-type atomic system via electromagnetically induced transparency (EIT). Under EIT conditions, the probe field envelopes obey the non-integrable nonlinear Schrödinger equations (NLSE) with or without the external potential, which result from the stark (Zeeman) effect contributed by an electric (magnetic) field. By adjusting the amplitude and width of the initial pulse, we can generate the high-dimensional rogue waves and obtain the phase-transition curves of high-dimensional rogue waves. In the system, the far-detuned electric field, the random weak magnetic field, and the Gauss weak magnetic field are not conducive to the excitation of high-dimensional rogue waves. The results not only provide a theoretical basis for the experimental realization or prevention of the high-dimensional rogue waves, but also prove the possibility of generating and controlling the rogue waves in other high-dimensional non-integrable systems.

High quality factor infrared notch filter with compact electromagnetically induced transparency metamaterial structure

A high quality factor infrared notch filter with compact electromagnetically induced transparency (EIT) structure is demonstrated theoretically and experimentally. The design process is carried out by using flowchart and finite-difference time-domain numerical method. The numerical quality factors of the notch filter are 2634 and 2462 at incident angles of 0° and 5° respectively. Heat power density distributions of the filter are also calculated to interpret the physical mechanism. A filter sample is fabricated and measured to verify the theoretical results.

Extending bandwidth sensitivity of Rydberg-atom-based microwave electrometry using an auxiliary microwave field

We demonstrate the use of an auxiliary microwave field to extend the bandwidth sensitivity of Rydberg-atom-based microwave electrometry. Electromagnetically induced transparency (EIT) and Autler-Townes (AT) splitting in Rydberg atom microwave electrometry provide advantageous sensitivity for the resonant detection of microwave (MW) fields because the Stark shift of the target Rydberg state takes the linear form of AT splitting. However, the sensitivity is reduced by several orders of magnitude for detuned MW fields because the Stark shift of the target Rydberg state depends on a weak nonlinear effect. We show that the auxiliary microwave field with appropriate Rabi frequency or detuning could shift the atomic energy levels to bring a particular Rydberg-Rydberg transition of interest for microwave sensing into resonance with the target microwave field. Using the atomic superheterodyne method, we verified the general method that regulates Rydberg energy levels using an auxiliary microwave field. The experimental results of this study confirm that this technique works efficiently for detecting microwave fields detuned by up to 100 MHz from resonance with the field-free Rydberg-Rydberg transition used for sensing. The measurement sensitivity of the detuned target field is increased by a factor of 10 compared with that achieved without the application of the auxiliary dressing field.

Tailoring Electromagnetic Responses in Terahertz Metasurface by Breaking the Structural Symmetry in T‐Shaped Resonators

Herein, the design of terahertz metasurface with symmetric T‐shaped resonators and the corresponding bright and dark modes are reported on. It is demonstrated that the dark mode evoked by breaking the structural symmetry is insensitive to the X‐polarized electric field and a typical electromagnetically induced transparency (EIT) effect is also observed in the numerical simulation when introducing a relatively low structural asymmetry where the dark and bright modes are modified to the same frequency. To explain the underlying mechanism, theoretical calculations based on the coupled Lorentz oscillator model are performed. In terms of the desirable fittings with the simulation results, it is confirmed that there exists the dark mode in the symmetric T‐shaped resonators and the coupling between the bright and dark modes enhanced by the structural–symmetry breaking is responsible for the observed EIT effect. It is shown in the results further that the structural asymmetry degree has close relation with the coupling strength resonance and can thereby greatly affect the oscillation resonance splitting in frequency that it is reflected by the change of the bandwidth of the transparency window. In addition, the experimental spectra showing the characteristic of broadband transparency window are explained by the excitation of the dark mode whose frequency deviates from the bright mode.

Metamaterials With Analogous Electromagnetically Induced Transparency and Related Sensor Designs—A Review

Electromagnetically induced transparency (EIT) originates from quantum physics, where a narrow transparent peak appears in the opaque band due to the destructive interference between quantum states of atoms and molecules. Similar phenomena can be realized based on strong-coupling resonators with a similar spectrum of transmission peaks and abrupt dispersion variations. These classical systems, ranging from elastic to optical, are named analogs of EIT. The sharp resonant peaks with high-quality factors in the spectrum exhibit powerful potentials in sensors with ultra-high sensitivity. In order to better understand the development history of EIT-like metamaterials and their specific applications in the field of sensors, this paper makes a brief review of the EIT-like phenomenon in metamaterials. Firstly, we conduct the universal mathematical formulation based on the coupling oscillator model. Then, we classify specific metamaterial designs and practical applications of EIT-like devices in acoustic, electromagnetic, and optical waves, respectively. We also summarize the recent technologies of dynamic modulations of EIT-like metamaterials and discuss future research directions.

Low-light-level spin–orbit splitting via structured light cross-Kerr interaction in coherent atomic media

We explore the spin–orbit coupling (SOC) mechanism for structured light in coherent atomic media with low-light-level cross-Kerr nonlinearity. Using the five-level M-type electromagnetic induced transparency (EIT) system as a prototype, we show that spin–orbit splitting for a weak spinor image can be generated by a weak trigger field carrying orbital angular momentum (OAM) at low-light intensity. By quantum-optical analogy, the paraxial focusing and defocusing of the two pseudo-spin states in the spinor image can be governed by a Pauli-like equation. More importantly, by changing the EIT parameters, especially the topological charge of the weak trigger field, the SOC-induced radial quantization of the spinor image can be rather significant, giving rise to positive or negative OAM-OAM mode separation in free space. This suggests that the separation can be flexibly controlled due to strong image-vortex interaction based on few-photon cross-Kerr modulation. Our findings may have the potential for all-optical OAM multiplexing and demultiplexing of structured light fields toward few-photon quantum control and multimode communication.

Switching of electromagnetic induced transparency in terahertz metasurface

We demonstrate functional switching of electromagnetic induced transparency (EIT) in terahertz (THz) metasurface. We first simulated and fabricated two metasurfaces that have light difference in their unit cell design. THz time domain spectroscopy of fabricated metasurfaces shows that two metasurfaces have almost similar transmission spectra but one of them possesses EIT while the second does not. To implement functional switching of EIT, we show numerically that characteristics of both metasurfaces can be achieved by a single hybrid metasurface containing a phase change material, Ge2Sb2Te5 (GST). GST has a large contrast in THz material properties in its crystalline and amorphous phases and its phase can be rapidly interchanged by external stimuli. We incorporated GST in the unit cell and show that phase change of GST portion in the metasurface unit cell at a specific location modulates the transmission spectra working as an EIT switch. EIT in the metasurface is attributed to coupling of two opposite phases bright resonance modes supported by the unit cell. The group delay of the transmitted THz radiation indicates that THz wave slows down significantly at EIT frequency. The dynamic interplay between two different responses within a single hybrid metasurface can have applications in biosensors, THz buffers, modulators, and other functional THz communication devices.

Weak-light solitons and their active control in Rydberg-dressed parity-time symmetry moiré optical lattices

We propose a physical setup to realize parity-time (PT) symmetric moiré optical lattices (ML) and nonlocal optical solitons in a cold Rydberg atomic system with electromagnetically induced transparency (EIT). We also show that based on the PT symmetry lattice strength and giant nonlocal Kerr nonlinearity originated from the strong, long-range atom–atom interaction, the system supports two-dimension (2D) nonlocal solitons with very low light intensity. By using numerical simulation method, we uncover the formation, properties, and dynamics of higher-order solitons and vortical ones. Our study opens a route for developing non-Hermitian nonlinear optics, especially for realizing and controlling high-dimensional weak-light optical solitons through adjustable PT-symmetric moiré lattice parameters and giant nonlocal optical nonlinearity.

Controllable electromagnetically induced transparency in an electrically tunable terahertz hybrid metasurface

Dynamic tuning of metasurfaces with active components is a prospective solution to improve their operation bandwidth. Here, we propose and experimentally demonstrate controllable electromagnetically induced transparency (EIT)-like response in a terahertz hybrid metasurface, where the classical EIT metallic pattern is coupled to the electrical biasing silicon carrier layer. Both the conductivity and thickness of the biased silicon layer can change significantly with increasing the external current. The electrically controllable hybrid metasurface shows complete electrical switching on the EIT-like response. The hybrid metasurface employing the state transition of the biased silicon layer between insulating and conductive states yields a substitute method to solve the narrowband operation bandwidth of photonic devices, which may inspire novel innovations on high-performance active terahertz applications.

Dressed Airy Vortex Beam in a Hot Atomic Medium

AbstractIntroducing vortices into an Airy beam by the interference between the lobes of the Airy beam for the first time, the modulation of Airy vortices is experimentally and theoretically investigated by electromagnetically induced transparency (EIT) effect and changing the number of side lobes of the Airy beam. The formation and disappearance of vortices in Airy beams can be caused by changing the number of side lobes. The EIT effect can induce the movement of vortex phase singularity by regulating the intensities of lobes in Airy beams. However, changing the number of side lobes can change the energy distribution of the lobes through the energy flow due to the self‐healing of Airy beams, thus causing the displacement of vortex phase singularity. In addition, the simulation of the Poynting vector shows that the less the side lobes are blocked, the more energy can be retained in the main lobe and the unblocked side lobes, so that the overall shape of the Airy beam can be better maintained. Such studies provide a new method to acquire and adjust Airy vortex beams and can be applied in the realm of optical micromanipulation.

Light shift induced modification of electromagnetically induced resonances in atomic vapor

We investigate the effects of a third laser on the electromagnetically induced transparency (EIT) spectrum obtained for the D2 line of 87Rb. The third laser converts a typical bi-chromatic laser-induced Λ type system into a four-level N type system. Our work considers two different configurations of N type system depending on whether the third laser is co-propagating or counter-propagating with respect to the other two. The effects of detuning on the EIT spectrum for both cases of N type systems have been experimentally studied. Our results demonstrate that for the counter-propagating case variation of detuning induces a switch from absorption to transmission. We interpret the experimental observations in terms of modification of light shifts by Doppler averaging within a dressed state formalism. Numerical results obtained using the density matrix formulation, which is in good agreement with the experimental results are also included to substantiate the experimental findings. We also find that in the presence of a magnetic field, due to the formation of certain subsystems that involves Zeeman sublevels, neither absorption nor transmission is observed in the probe transmission spectrum. We define these as the “missing resonance” peaks. We propose methods for recovering these peaks in the probe transmission spectrum.

Application of magnetically induced [formula omitted] atomic transitions of cesium atoms in strong magnetic fields

In this work, magnetically induced (MI) transitions of the Cs atoms in strong magnetic fields up to 6 kG, and their applications in spectroscopy are studied experimentally and theoretically. An attractive feature of these transitions is their large frequency shift slope in a magnetic field (−4 MHz/G). Therefore, in strong magnetic fields the frequency shift of MI transitions reaches several tens of GHz and importantly, these transitions do not overlap with others, which is of practical interest for possible use in new frequency ranges. To implement the process of electromagnetically induced transparency (EIT) in a strong magnetic field (1–2 kG), the MI Fg=4→Fe=2 transitions were first used at the frequency of probe radiation, while the frequency of coupling radiation is resonant the Fg=3→Fe=2 transitions. To form the EIT resonance, a cell of sub-micron thickness filled with Cs atom vapors was used, along with strong permanent magnets.

Inverse design of slow light devices at telecommunication band based on metamaterials using a deep learning attempt

Slow light devices have important applications in many fields such as optical communication, optical storage, optical signal shaping and synchronization. Although a variety of high-performance slow light devices can be purchased in the market, it is still a worthwhile research topic to design slow light devices according to specific wavelengths and requirements. Here we employ machine learning method to inverse design electromagnetically induced transparency (EIT) based slow light devices in communication band using metal–dielectric hybrid metamaterials. Three characteristic points of transmittance as well as the group refractive index and bandwidth are chosen as input parameters. By replacing the complex fully connected layer with a one-dimensional convolutional neural network (1DCNN) layer to optimize the fully connected network, the proposed model can break the limitation of passive modulation and find the best slow light structure parameters. The slow light parameters could reach a bandwidth of 38.71 nm and average group refractive index of 10.51. In addition, the model can predict hybrid metamaterial structure parameters of slow light devices in the communication band from 1400 nm to 1600 nm. By combining active and passive modulation technologies, our proposed method improves the adjustment range of design parameters of slow light devices. The procedure can be potentially applied in the design of other nano optical devices.

Optimal optical Ferris wheel solitons in a nonlocal Rydberg medium.

We propose a scheme for the creation of stable optical Ferris wheel (OFW) solitons in a nonlocal Rydberg electromagnetically induced transparency (EIT) medium. Depending on a careful optimization of both the atomic density and the one-photon detuning, we obtain an appropriate nonlocal potential provided by the strong interatomic interaction in Rydberg states that can perfectly compensate for the diffraction of the probe OFW field. Numerical results show that the fidelity remains larger than 0.96, while the propagation distance has exceeded 160 diffraction lengths. Higher-order OFW solitons with arbitrary winding numbers are also discussed. Our study provides a straightforward route to generate spatial optical solitons in the nonlocal response region of cold Rydberg gases.

Accessing and manipulating dispersive shock waves in a nonlinear and nonlocal Rydberg medium

Dispersive shock waves (DSWs) are fascinating wave phenomena occurring in media when nonlinearity overwhelms dispersion (or diffraction). Creating DSWs with low generation power and realizing their active controls is desirable but remains a longstanding challenge. Here, we propose a scheme to generate weak-light DSWs and realize their manipulations in an atomic gas involving strongly interacting Rydberg states under the condition of electromagnetically induced transparency (EIT). We show that for a two-dimensional (2D) Rydberg gas a weak nonlocality of optical Kerr nonlinearity can significantly change the edge speed of DSWs and induces a singular behavior of the edge speed and hence an instability of the DSWs. However, by increasing the degree of the Kerr nonlocality, the singular behavior of the edge speed and the instability of the DSWs can be suppressed. We also show that in a 3D Rydberg gas, DSWs can be created and propagate stably when the system works in the intermediate nonlocality regime. Due to the EIT effect and the giant nonlocal Kerr nonlinearity contributed by the Rydberg-Rydberg interaction, DSWs found here have extremely low generation power. In addition, an active control of DSWs can be realized; in particular, they can be stored and retrieved with high efficiency and fidelity through switching off and on a control laser field. The results reported here are useful not only for unveiling intriguing physics of DSWs but also for finding promising applications of nonlinear and nonlocal Rydberg media.

Influence of spontaneously generated coherence on absorption, dispersion, and group index in a five-level cascade atomic system

By solving the density matrix equations in the steady state, we have derived analytical expressions for the absorption, dispersion, and group index of a five-level cascade-type atomic system as functions of laser intensity and frequency, spontaneously generated coherence (SGC), and relative phase of applied fields. The influences of SGC and relative phase on absorption, dispersion, and group index of this system under electromagnetically induced transparency (EIT) are studied. It is shown that the three EIT windows of system become deeper and narrower as the strength of SGC increases. These lead to an increase in the slope and the amplitude of the dispersion curves at three EIT windows. As a result, the amplitude of the group index at these three EIT windows also becomes larger when the strength of SGC increases. In particular, the group index can easily be switched between negative and positive values i.e., the light propagation can easily be converted between superluminal to subluminal modes by adjusting the strength of SGC, relative phase or the coupling laser intensity.

Multiple Phase Stepping Generation in Alkali Metal Atoms: A Comparative Theoretical Study

We theoretically demonstrated optical phase switches in light storage-like experiments. Typical light storage (LS) and retrieval experiments consist of the probe field in the probe channel with writing and reading fields across the drive branch, as well as its recovery. The probe and first drive pulses as the standard electromagnetically induced transparency (EIT) effect of storing light are used in the proposed scheme for the atomic excitations. A train of probe pulses is used after a short storage period to induce Raman gain in the drive channel. The proposed scheme was applied to alkali-metal atoms such as 23Na, 87Rb, and 39K vapours. Spatiotemporal phase variations for generated drive pulses were found to shape in the form of discrete phase distributions. The proposed approach in the process of obtaining phase discrete distributions for different irradiation intensities was tested. For weak fields, the discrete distributions were distinct as a result of the differences in the upper hyperfine structure (hf) and the atomic relaxations. However, for moderate fields, the discrete phase distributions are smeared by the atomic relaxations.

Tunable Transparency and Group Delay in Cavity Optomechanical Systems with Degenerate Fermi Gas

We theoretically investigate the optical response and the propagation of an external probe field in a Fabry–Perot cavity, which consists of a mechanical mode of trapped, ultracold, fermionic atoms inside and simultaneously driven by an optical laser field. We investigate the electromagnetically-induced transparency due to coupling of the optical cavity field with the collective density excitations of the ultracold fermionic atoms via radiation pressure force. Moreover, we discuss the variations in the phase and group delay of the transmitted probe field with respect to effective cavity detuning as well as pumping power. It is observed that the transmitted field is lagging in this fermionic cavity optomechanical system. Our study shall provide a method to control the propagation as well as the speed of the transmitted probe field in this kind of fermionic, ultracold, atom-based, optomechanical cavity system, which might have potential applications in optical communications, signal processing and quantum information processing.

A practical guide to electromagnetically induced transparency in atomic vapor

This tutorial introduces the theoretical and experimental basics of electromagnetically induced transparency (EIT) in thermal alkali vapors. We first give a brief phenomenological description of EIT in simple three-level systems of stationary atoms and derive analytical expressions for optical absorption and dispersion under EIT conditions. Then we focus on how the thermal motion of atoms affects various parameters of the EIT system. Specifically, we analyze the Doppler broadening of optical transitions, ballistic versus diffusive atomic motion in a limited-volume interaction region, and collisional depopulation and decoherence. Finally, we discuss the common trade-offs important for optimizing an EIT experiment and give a brief ‘walk-through’ of a typical EIT experimental setup. We conclude with a brief overview of current and potential EIT applications.