The absorption of photons in a three-level atom can be controlled and manipulated by applying a coherent drive at one of the atomic transitions. The situation where the absorption is fully canceled, and the atom thus has been turned completely transparent, has been coined electromagnetically induced transparency (EIT). The characteristics of EIT is a narrow transparency window associated with a fluorescence quench at its center frequency, indicating that inelastic scattering at this particular point is suppressed. The emergence of EIT-like transparency windows is common in waveguide quantum electrodynamics (QED) when multiple closely spaced quantum emitters are coupled to a waveguide. The transparency depends on the separation and energy detuning of the atoms. In this work, we study a number of different setups with two-level atoms in waveguide QED that all exhibit EIT-like transparency windows. Unlike the case of a genuine three-level atom, no drive fields are required in the systems we consider, and the coherent coupling of energy levels is mediated by the waveguide. We specifically distinguish between systems with genuine EIT-like dynamics and those that exhibit a transparency window but lack the fluorescence quench. The systems that we consider consist of both small and giant atoms, which can be experimentally realized with artificial atoms coupled to either photons or phonons. These systems can offer a simpler route to many EIT applications since the need for external driving is eliminated.
The absorption of photons in a three-level atom can be controlled and manipulated by applying a coherent drive at one of the atomic transitions. The situation where the absorption is fully canceled, and the atom thus has been turned completely transparent, has been coined electromagnetically induced transparency (EIT). The characteristics of EIT is a narrow transparency window associated with a fluorescence quench at its center frequency, indicating that inelastic scattering at this particular point is suppressed. The emergence of EIT-like transparency windows is common in waveguide quantum electrodynamics (QED) when multiple closely spaced quantum emitters are coupled to a waveguide. The transparency depends on the separation and energy detuning of the atoms. In this work, we study a number of different setups with two-level atoms in waveguide QED that all exhibit EIT-like transparency windows. Unlike the case of a genuine three-level atom, no drive fields are required in the systems we consider, and the coherent coupling of energy levels is mediated by the waveguide. We specifically distinguish between systems with genuine EIT-like dynamics and those that exhibit a transparency window but lack the fluorescence quench. The systems that we consider consist of both small and giant atoms, which can be experimentally realized with artificial atoms coupled to either photons or phonons. These systems can offer a simpler route to many EIT applications since the need for external driving is eliminated.
The nonlocal emitter-waveguide coupling, which gives birth to the so called giant atom, represents a new paradigm in the field of quantum optics and waveguide QED. In this paper, we investigate the single-photon scattering in a one-dimensional waveguide on a two-level or three-level giant atom. Thanks to the natural interference induced by the back and forth photon transmitted/reflected at the atom-waveguide coupling points, the photon transmission can be dynamically controlled by the periodic phase modulation via adjusting the size of the giant atom. For the two-level giant-atom setup, we demonstrate the energy shift which is dependent on the atomic size. For the driven three-level giant-atom setup, it is of great interest that, the interference effect between different atomic transition paths, can lead to a complete transmission window, analogous to the electromagnetically induced transparency and beyond the two-photon resonance mechanism, and the width of the transmission valleys (reflection range) is tunable in terms of the atomic size. Our investigation will be beneficial to the photon or phonon control in quantum network based on mesoscopical or even macroscopical quantum nodes involving the giant atom.
Abstract Electromagnetically induced transparency (EIT) in five-level atomic systems is theoretically investigated for three representative configurations: M-, inverted-Y, and K-type systems driven by a weak probe field and three control laser fields. The different coupling schemes produce different quantum interference pathways and two-photon resonance conditions, leading to markedly different EIT spectra. The M-type configuration exhibits one, two, and three well-resolved transparency windows as successive control fields are introduced. In contrast, the inverted-Y configuration produces broader transparency windows because of the overlap of multiple interference channels, whereas the K-type configuration exhibits only a single EIT window when all control fields are resonant. Multiple transparency windows in the K-type system appear after introducing appropriate coupling-field detunings. Doppler broadening at room temperature significantly broadens the absorption spectrum and reduces the transparency depth, while preserving the number and positions of the EIT windows. These results demonstrate that the coupling scheme plays an important role in determining the formation and evolution of multi-window EIT spectra and identify the characteristics of the three five-level configurations for multi-channel quantum-optical applications, as well as for the experimental observation of EIT spectra in five-level configurations.
Abstract We investigate the single-photon transport properties in a hybrid waveguide quantum electrodynamics system, in which a one-dimensional waveguide is simultaneously coupled to a cavity and a driven Λ-type three-level atom. The cavity and the atom are also coupled to each other. We show that when the waveguide is coupled to the cavity and the atom at the same point, double electromagnetically induced transparency (EIT) can be observed from the system. The physical mechanism of the double EIT effect has been given by setting up the eigenstate structure for the whole system. When the waveguide is coupled to the cavity and the atom at different points, we demonstrate that the single-photon transmission spectra can be effectively controlled by adjusting the relative separation between the cavity and the atom. Moreover, this non-zero relative separation can lead to the occurrence of the controllable nonreciprocal scattering effect. These results have potential applications in realization of photonic coherent control.
Engineering light-matter interactions at the quantum level has been central to the pursuit of quantum optics for decades. Traditionally, this has been done by coupling emitters, typically natural atoms and ions, to quantized electromagnetic fields in optical and microwave cavities. In these systems, the emitter is approximated as an idealized dipole, as its physical size is orders of magnitude smaller than the wavelength of light. Recently, artificial atoms made from superconducting circuits have enabled new frontiers in light-matter coupling, including the study of ``giant'' atoms which cannot be approximated as simple dipoles. Here, we explore an implementation of a giant artificial atom, formed from a transmon qubit coupled to propagating microwaves at multiple points along an open transmission line. The nature of this coupling allows the qubit radiation field to interfere with itself, leading to some striking giant-atom effects. For instance, we observe strong frequency-dependent couplings of the qubit energy levels to the electromagnetic modes of the transmission line. Combined with the ability to in situ tune the qubit energy levels, we show that we can modify the relative coupling rates of multiple qubit transitions by more than an order of magnitude. By doing so, we engineer a metastable excited state, allowing us to operate the giant transmon as an effective lambda system where we clearly demonstrate electromagnetically induced transparency.
Using density matrix eqution, the absorption and dispersion properties of a A-type four-level system driven by coherent fields are investigated. The result obtained by means of numerical method indicates that by adjusting the intensity of Rabi frequencies of the coherent field in the steady state, three, double or single electromagnetically induced transparency (EIT) can appear explicitly in this system. And the explanations of these phenomena are given by using the dressed states. In the three EIT, the location of transparent windows can be manipulated by controlling the detuning of the driving field. What's more, it is also found that the medium shows a large refractive index at each transparency window, and the group velocity of the probe laser can be enhanced.
Abstract We study the reflected and transmitted output properties of a weak probe field incident upon an optomechanical cavity separated by a membrane oscillator and filled with two-level cold atoms. We find that electromagnetically induced transparency (EIT) and optomechanically induced transparency (OMIT) may simultaneously exist owing to separate cavity–atom coupling and cavity-oscillator coupling, respectively. It is more interesting that the hybrid EIT and OMIT phenomena can be manipulated on demand to exhibit various spectral features on dispersion, transmission, and reflection. In particular, we discover the new hybrid double transparency window (a narrow OMIT dip appearing inside the wide EIT window), analogous to double EIT for a four-level atomic system in inverted-Y configuration. Meanwhile, we can reduce the hybrid EIT–OMIT to a single EIT or OMIT shape by changing the magnitude of the driving field power or the atomic number as desired. Furthermore, by changing the system’s detuning it is possible to change the location and the profile of the EIT, therefore switching the shape of the hybrid EIT–OMIT from symmetric to asymmetric, as well as for the profile to change from a absorption dip-like EIT to dispersion-like EIT in both real and imaginary parts of the output probe field. Also, by modifying system’s detuning we have control over the distribution of the output energy, something difficult to achieve with only one of the sub-systems available.