Non-rotating Wave Approximation Research Articles

Perfect optomechanically induced transparency and slow light in an Rydberg atom-assisted optomechanical system

Rydberg atoms have attracted considerable attention due to their several singular properties, such as strong long-range interactions, extremely long lifetimes, and very large polarizability. These characteristics make Rydberg atoms a good candidates for cavity quantum electrodynamics, quantum information, and many-body physics. Recently, the study of optomechanics has become a rapidly developing field due to its important applications in cooling of mechanical resonators, implementing precision measurements, slowing light, and preparing quantum entanglement. Obviously, optomechanical systems pave the way for quantum information processing and quantum communication. Specially, there is significant interest in quantum optomechanics due to its high compatibility that can be combined, to build hybrid systems for certain purposes, with the ultracold atoms, a superconducting single electron transistor, a magnetostrictive actuation, a charged oscillator resonator, etc. In this work, we investigate the optomechanically induced transparency (OMIT) and the resulting effect of slow light in a hybrid system composed of a Rydberg atomic ensemble embedded inside a simple optomechanical cavity. As a typical effect of destructive quantum interference, OMIT is widely used in quantum optics and quantum information processing. Based on the Rydberg blockade effect, a Rydberg atomic ensemble in the same blockade region embedded inside an optomechanical cavity can be regarded as a superatom that contains only a single Rydberg excitation. Therefore, the problem of exponentially increasing system size with the number of atoms increasing can be circumvented easily. The hybrid system becomes a coupling between a Rydberg superatom and an optomechanical cavity and the coupling strength is enhanced by a factor of square root of the number of atoms in the ensemble. In this system, the perfect OMIT, namely, an ideal OMIT dip with a very narrow window, can be attained when an effect of non-rotating wave approximation (NRWA) is considered. Further, we demonstrate that the term of NRWA plays a key important role in achieving perfect OMIT by comparing the optomechanical spectra obtained with and without NRWA effects. Our results show that in the resolved sideband regime the higher the quality factor of cavity is, the stronger the slow light effect becomes in the window of the perfect OMIT. Particularly, in achieving the ultraslow light, the long lifetime of the Rydberg atom shows its superiority.

Ideal optomechanically induced transparency generation in a cavity optoelectromechanical system* *Project supported by the Natural Science Foundation of Guangxi Province, China (Grant Nos. 2018GXNSFBA281003, 2019GXNSFAA245034, and AD19245180) and Science Fund of Tonghua Normal University (Grant No. 202017ND).

The ideal optomechanically induced transparency effects of an output probe field are investigated in a cavity optoelectromechanical system, which is composed of an optical cavity, a charged mechanical resonator, and a charged object. Although the charged mechanical resonator damping rate is nonzero, the ideal optomechanically induced transparency can still appear due to the non-rotating wave approximation effect in the system. The location of optomechanically induced transparency dip can be controlled via the Coulomb coupling strength. In addition, we find that both the transparency window width and the maximum dispersion curve slope are closely related to the optical cavity decay rate.

Controllable Photon Transport in a Three-Mode Optomechanical System with the Non-Rotating Wave Approximation Effect

We propose a scheme for realizing controllable photon transport in a three-mode optomechanical system comprising one cavity and two mechanical modes. We found that the non-rotating wave approximation effect can cause the ideal optomechanically induced transparency of the output field. The effects of the cavity mode decay rate on the width of the optomechanically induced transparency window, the dispersion curve slope are discussed in the resolved sideband regime and the unresolved sideband regime.

Optomechanically induced optical responses with non-rotating wave approximation

Slow light propagation is an important phenomenon in quantum optics. Here, we theoretically study the properties of slow light in a simple optomechanical system considering an effect of non-rotating wave approximation (NRWA) that was ignored in previous related works. With the NRWA effect, the ultraslow light can be easily achieved at the window of optomechanically induced transparency, especially in unresolved sideband regime. From the theoretical results, we find the upper bound of the time delay is exactly the mechanical ringdown time which can last for several minutes (mHz linewidth) in recent experiments. Additionally, the interesting phenomena of the perfect optomechanically induced transmission and absorption are studied in the system with the NRWA effect. We believe the results can be used to control optical transmission in modern optical networks.

基于非旋转波近似效应的完美光力诱导透明和放大

基于非旋转波近似效应的完美光力诱导透明和放大

Signal transmission and parameter measurement in quantum bits interacting with a single-mode radiation field

Quantum systems can display the quantum chaos characteristics under non-rotating wave approximation. Because of the complex multi-body effect, the inevitability of coupling with the environment and the existence of uncertainty relation, some parameters in quantum system are often uncertain. In order to determine the properties of quantum system, we need to accurately measure any parameters in the system. In this work, we first analyse the characteristics of quantum bits interacting with a single-mode radiation field. On this basis, we design a unique technique to accurately measure the uncertain parameter in the quantum bits. Finally, we complete the synchronization transmission of signal in quantum bits based on the sliding mode control technology.

Optomechanically induced transparency and gain

Optomechanically induced transparency is an important quantum phenomenon in cavity optomechanics. Here, we study the properties of optomechanically induced transparency in the simplest optomechanical system (consisting of one cavity and one mechanical resonator) considering the effect of non-rotating wave approximation (NRWA) that was ignored in previous works. With the NRWA effect, we find the ideal optomechanically induced transparency dip can be easily achieved, and the width of optomechanically induced transparency dip can become very narrow especially in unresolved sideband regime. Finally, we study the properties of optomechanically induced gain, and give the analytic expression about the maximum value of gain.

Fano-Agarwal couplings and non-rotating wave approximation in single-photon timed Dicke subradiance

Recently a new class of single-photon timed Dicke (TD) subradiant states has been introduced with possible applications in single-photon–based quantum information storage and on demand ultrafast retrieval (Scully M. O., Phys. Rev. Lett., 115 (2015) 243602). However, the influence of any kind of virtual processes on the decay of these new kind of subradiant states has been left as an open question. In the present paper, we focus on this problem in detail. In particular, we investigate how pure Fano-Agarwal couplings and other virtual processes arising from non-rotating wave approximation impact the decay of otherwise sub- and superradiant states. In addition to the overall virtual couplings among all TD states, we also focus on the dominant role played by the couplings between specific TD states.

Dynamical Casimir Effect and Collective Excitation Effect at Finite Temperature Without the Rotating-Wave Approximation

The dynamical Casimir effect and the collective excitation effect are investigated in a resonantly vibrating cavity filled with a gas of two-level atoms without the rotating-wave approximation at finite temperature. Compared with the condition of the rotating-wave approximation, the created photons and the created excitons are more under the non-rotating wave approximation at different temperatures and different total coupling strengths. The numerical results show that the counter-rotating wave terms enhance the dynamical Casimir effect and the collective excitation effect at finite temperature.

Quantum Fisher information and spin squeezing in the interaction system of light and matter

Fisher information is an important concept in estimation theory, which has recently been found closely related with the criteria of the entanglement in quantum information. Under the condition of non-rotating wave approximation, the classical phase space of the Dicke model displays chaotic dynamic properties. This paper studies the quantum Fisher information and the dynamic properties of spin squeezing in the interaction system of light and matter described in the Dicke model. Results reveal that, in the short-time instant state, wherever the initial state is, in a regular region or a chaotic region, the system displays entanglement; but in the long-time stable state, when the initial state is in the regular region, the system entanglement disappears, however, when the initial state is in the chaotic region, the system is always entangled. Compared with the spin-squeezing dynamic properties of the system, Fisher information is found to be able to effectively characterize quantum chaos. On further examination on the dynamic evolvement properties of the density matrix and purity of the system when in the regular and chaotic regions, we find that chaos gives rise to decoherence of the system, showing that quantum information become more sensitive to chaos.

Entanglement of a two-particle Gaussian state interacting with a heat bath

The effect of a thermal reservoir is investigated on a bipartite Gaussian state. We derive a pre-Lindblad master equation in the non-rotating wave approximation for the system. We then solve the master equation for a bipartite harmonic oscillator Hamiltonian with entangled initial state. We show that for strong damping the loss of entanglement is the same as for freely evolving particles. However, if the damping is small, the entanglement is shown to oscillate and eventually tend to a constant non-zero value. • We derive and solve a pre-Lindblad master equation. • We examine the dynamics of the entanglement in a two-particle system. • We find that if the two particles are interacting, the entanglement does not vanish.

Level crossing in a two-photon Jaynes—Cummings model

In this paper, the energy spectrum of the two-photon Jaynes—Cummings model (TPJCM) is calculated exactly in the non-rotating wave approximation (non-RWA), and we study the level-crossing problem by means of fidelity. A narrow peak of the fidelity is observed at the level-crossing point, which does not appear at the avoided-crossing point. Therefore fidelity is perfectly suited for detecting the level-crossing point in the energy spectrum.

Short-time quantum detection: Probing quantum fluctuations

In this work we study the information provided by a detector click on the state of an initially excited two level system. By computing the time evolution of the corresponding conditioned probability beyond the rotating wave approximation, as needed for short time analysis, we show that a click in the detector is related with the decay of the source only for long times of interaction. For short times, non-rotating wave approximation effects, like self-excitations of the detector, forbid a na\"{i}ve interpretation of the detector readings. These effects might appear in circuit QED experiments.

Quantum evolution of entanglement property in two-qubit and oscillator coupling system

Under the non-rotating wave approximation, the quantum evolution of entanglement property of a two-qubit and oscillator coupling system is accurately investigated by the method of coherent-state orthogonalization expansion. The property of the ground state for qubit-oscillator system and the difference between qubit-oscillator entanglement and qubit-qubit entanglement when resonant vibration occurs are discussed. The calculation results show that when the external field is not taken into consideration, the qubit-qubit entanglement reduces from 1 to 0 rapidly with the increase of coupling strength, indicating the strong sensitivity of the entanglement to the coupling strength. On the contrary, with the increase of the coupling the qubit-oscillator entanglement rises from 0, but does not reach the maximum value 2. At the beginning, when the two qubits do not entangle, the vacuum field does not lead to the entanglement in weak coupling. However, the strong coupling can induce the sudden appearance of the entanglement.

Relations of classical-quantum correspondencein Dicke model

Dicke model displays quantum chaotic dynamic properties in the non-rotating wave approximation. On the basis of properties of the classical phase space of Dicke model, we employ the one-to-many notion, namely, evolution from one point on the classical phase space to two initial coherent states. Then we obtain a good quantum phase space, which corresponds to the classical one, by using the method of averaging the statistical entangled values of two initial states in the evolution. The numerical computation shows that classical chaos can promote the origination of bipartite entanglement, and simultaneously, the average entanglement can be regarded as the signature of quantum chaos. A good classica-quantum correspondence can be obtained by using the average entanglement.

Coherent control of atomic excitation using off-resonant strong few-cycle pulses

We study the dynamics of a two-level system driven by an off-resonant few-cycle pulse which has a phase jump $\phi$ at $t=t_{0}$, in contrast to many cycle pulses, under non rotating-wave approximation (NRWA). We give a closed form analytical solution for the evolution of the probability amplitude $|C_{a} (t)|$ for the upper level. Using the appropriate pulse parameters like phase-jump $\phi$, jump time $t_{0}$, pulse width $\tau$, frequency $\nu$ and Rabi frequency $\Omega_{0}$ the population transfer, after the pulse is gone, can be optimized and for the pulse considered here, enhancement of $10^{6}-10^{8}$ factor was obtained.

Exact calculations of the energy spectra and the dynamical properties of a two-level system

Applying the method of coherent-state orthogonalization expansion，the energy spectra and the dynamical properties of the Jaynes-Cummings model with non-rotating wave approximation are calculated exactly. By comparison with the approximate analytical solutions, it is found that the approximate analytical solutions agree with our numerical exact solutions well both in weak coupling regime and in strong coupling regime, but not so well in intermediate strength coupling regime.

Sideband structure spontaneous spectrum without the rotating wave approximation

The effects of the non-rotating wave approximation (non-RWA) on the spontaneous emission of a V-type three-level atom are studied, where the excited states are coupled to a common ground state by a weak laser field and the upper-level doublet is driven by a strong microwave field. When the non-RWA is applied to the interaction of the atom with the microwave field, for some values of the parameters involved, the spontaneous emission spectrum is comprised of a central peak and a series of sidebands with a constant spacing of the microwave frequency, and the central peak and/or sidebands can be split into two components. The physical interpretation of the spectral characteristics is given in light of the dressed states.

Modified photon-added coherent states: Generation and relatedentangled states

We construct one new type of quantum state that we call the modified photon-added coherent state (MPACS) of the radiation field. These states are created by repeatedly applying the Hermitian operator (a + a+) to the coherent state m times. It turns out that these states are the superpositions of the coherent and the photon-added coherent states, and have highly nonclassical behavior depending on the excitation m and other parameters. The one-mode and two-mode modified entangled coherent states are also studied. MPACS can be generated through the atom-field interaction under the nonrotating wave approximation. PACS Nos.: 42.50.Dv, 03.65.Ca, 03.65.Ud

Ultrasharp lines without the rotating wave approximation

We study the effects of the non-rotating wave approximation (non-RWA) on the spontaneous emission of a Λ-type three-level atom, where the metastable states are coupled to a common excited state by a weak laser field and the lower-level doublet is driven by a strong microwave field. When the non-RWA is applied to the interaction of the atom with the microwave field, the spontaneous emission spectrum is comprised of a series of ultrasharp lines. The physical interpretation of the spectral characteristics is given in light of the dressed states.