Cascade Three-level Atom Research Articles

Injected coherence and phase control in the tunneling of ultra slow three-level atoms

Our research aims to investigate the impact of injecting atomic coherence on the phase tunneling time of ultra slow cascade three-level atoms traversing through high-quality cavities. Prior to interacting with the cavity in the Fock state, the atoms are initially prepared in a superposition of the two upper levels. Our study has demonstrated that the coherence of the injected atoms can be tuned to control the phase time. Specifically, we have observed that the injected coherence can regulate the peak values and sub-superclassical nature of the traversal time. Moreover, we have investigated how the number of superclassical peaks and resonances in the tunneling time curve can be influenced by the cavity length and de Broglie waves of the atom. Additionally, we have discovered that the phase time behavior is not only affected by the center-of-mass (CM) motion but also by the atom–field detuning and the final internal state of the transmitted atoms. These findings have potential implications for developing and controlling ultracold atom-based technologies, such as quantum sensors, quantum information processing, and quantum simulation.

Dephasing of ultracold cesium 80D5/2-Rydberg electromagnetically induced transparency.

We study Rydberg electromagnetically induced transparency (EIT) of a cascade three-level atom involving 80D5/2 state in a strong interaction regime employing a cesium ultracold cloud. In our experiment, a strong coupling laser couples 6P3/2 to 80D5/2 transition, while a weak probe, driving 6S1/2 to 6P3/2 transition, probes the coupling induced EIT signal. At the two-photon resonance, we observe that the EIT transmission decreases slowly with time, which is a signature of interaction induced metastability. The dephasing rate γOD is extracted with optical depth OD = γODt. We find that the optical depth linearly increases with time at onset for a fixed probe incident photon number Rin before saturation. The dephasing rate shows a nonlinear dependence on Rin. The dephasing mechanism is mainly attributed to the strong dipole-dipole interactions, which leads to state transfer from nD5/2 to other Rydberg states. We demonstrate that the typical transfer time τ0(80D) obtained by the state selective field ionization technique is comparable with the decay time of EIT transmission τ0(EIT). The presented experiment provides a useful tool for investigating the strong nonlinear optical effects and metastable state in Rydberg many-body systems.

Precise measurement of a weak radio frequency electric field using a resonant atomic probe**Project supported by the National Key R&D Program of China (Grant No. 2017YFA0304203), the National Natural Science Foundation of China (Grant Nos. 61475090, 61675123, 61775124, and 11804202), the State Key Program of National Natural Science of China (Grant Nos. 11434007 and 61835007), and Changjiang Scholars and Innovative

We present a precise measurement of a weak radio frequency electric field with a frequency of ≲ 3 GHz employing a resonant atomic probe that is constituted with a Rydberg cascade three-level atom, including a cesium ground state |6S1/2⟩, an excited state |6P3/2⟩, and Rydberg state |nD5/2⟩. Two radio frequency (RF) electric fields, noted as local and signal fields, couple the nearby Rydberg transition. The two-photon resonant Rydberg electromagnetically induced transparency (Rydberg-EIT) is employed to directly read out the weak signal field having hundreds of kHz difference between the local and signal fields that is encoded in the resonant microwave-dressed Rydberg atoms. The minimum detectable signal fields of ESmin = 1.36 ± 0.04 mV/m for 2.18 GHz coupling |68D5/2⟩ → |69P3/2⟩ transition and 1.33 ± 0.02 mV/m for 1.32 GHz coupling |80D5/2⟩ → |81P3/2⟩ transition are obtained, respectively. The bandwidth dependence is also investigated by varying the signal field frequency and corresponding −3 dB bandwidth of 3 MHz is attained. This method can be employed to perform a rapid and precise measurement of the weak electric field, which is important for the atom-based microwave metrology.

Precise Measurement of Hyperfine Structure of Cesium 7S1/2 Excited State

We present a precise measurement of the hyperfine structure of cesium 7 S 1 / 2 excited state by employing electromagnetically induced spectroscopy (EIS) with a cesium three-level cascade ( 6 S 1 / 2 − 6 P 3 / 2 − 7 S 1 / 2 ) atom in a room temperature vapor cell. A probe laser, λ p = 852 nm, was coupled to a transition | 6 S 1 / 2 ⟩ → | 6 P 3 / 2 ⟩ , related frequency locked to the resonance hyperfine transition of | 6 S 1 / 2 ⟩ → | 6 P 3 / 2 ⟩ with a Fabry–Perot (FP) cavity and an electro-optic modulator (EOM). A coupling laser, λ c = 1470 nm, drove the | 6 P 3 / 2 ⟩ → | 7 S 1 / 2 ⟩ transition with the frequency scanned over the | 6 P 3 / 2 ⟩ → | 7 S 1 / 2 ⟩ transition line. The hyperfine level interval was extracted to be 2183.61 ± 0.50 MHz by analyzing EIS spectroscopy. The optical–optical double-resonance (OODR) spectroscopy is also presented for comparison, with the corresponding value of the hyperfine level interval being 2183.48 MHz ± 0.04 MHz, and the measured hyperfine splitting of excited 7 S 1 / 2 state is shown to be in excellent agreement with the previous work.

Manipulation and improvement of multiphoton blockade in a cavity-QED system with two cascade three-level atoms

We present a study of manipulating the multiphoton blockade phenomenon in a single mode cavity with two ladder-type three-level atoms. Combining the cavity QED with electromagnetically induced transparency technique, we show that it is possible to actively manipulate the photon blockade when two atoms are in phase radiations. As a result, the two-photon blockade can be changed to three-photon blockade by changing the control field Rabi frequency. In the case of out-phase radiations, we show that the three-photon blockade can be improved with enhanced mean photon number. In addition, we show that the nonclassical field with sub-Poissonian distribution can be changed to the classical field with super-Poissonian distribution by tuning the Rabi frequency of the control field. The results presented in this work open up the possibility for achieving a two-photon gateway operation, which could be used in network of atom-cavity systems to control the quantum property of photons leaking from the cavity.

Entropy squeezing for three-level atom interacting with a single-mode field**Project supported by the National Natural Science Foundation of China (Grant No. 11374096).

The entropy squeezing for a three-level atom interacting with a single-model field is studied. A general definition of entropy squeezing for three-level atom is given according to entropic uncertainty relation of three-level system, and the calculation formalism of entropy is derived for a cascade three-level atom. By using numerical calculation, the entropy squeezing properties of a cascade three-level atom are examined. Our results show that, three-level atom can generate obvious entropy squeezing effect via choosing appropriate superposition state of three-level atom. Our results are meaningful for preparing three-level system information resources with ultra-low quantum noise.

Entanglement formulation in the framework of electrically pumped laser cavity

We analyze electrically pumped atomic cavity coupled to a two-mode vacuum reservoirs via a single-port mirror whose open cavity contains N nondegenerate three-level cascade atoms. We carry out our analysis by putting the noise operators associated with a vacuum reservoir in normal order. It is found that unlike the mean photon number, the quadrature squeezing and the degree of entanglement do not depend on the number of atoms. This implies that the quadrature squeezing and the degree of entanglement of the cavity light do not depend on the number of photons. We have also shown that the light generated by the three-level laser is in a squeezed and entangled state, with maximum quadrature squeezing and degree of entanglement being 50%. Moreover, the mean photon number of the system in which the laser operating at threshold and above threshold does not depend on the spontaneous decay constant.

Entanglement of Optical and Mechanical Modes Enhanced in Distant Optomechanical Systems by Atomic Coherence

We present a scheme for three-level cascade atoms to entangle various optical and mechanical modes of two coupled cavity optomechanical system. With the existence of atomic mediums, our study shows that the larger stationary macroscopic entanglement of distant optomechanical systems can be obtained and reaches the maximum at the same effective detuning. Furthermore, we find that it is insensitive to the cavity decay rate for the entanglement between the two distant movable mirrors, and between the mirror and the adjacent or the distant cavity mode, which compensates for the effects of the cavity dissipation.

双模光场与级联三能级原子在非旋波近似下的量子纠缠

双模光场与级联三能级原子在非旋波近似下的量子纠缠

Quantum coherence and population transfer in a driven cascade three-level artificial atom

We present an experimental investigation on the spectral characteristics of an artificial atom "transmon qubit" constituting a three-level cascade system ({\Xi}-system) in the presence of a pair of external driving fields. We observe two different types of Autler-Townes (AT) splitting: type I, where the phenomenon of two-photon resonance tends to diminish as the coupling field strength increases, and type II, where this phenomenon mostly stays constant. We find that the types are determined by the cooperative effect of the decay rates and the field strengths. Theoretically analyzing the density-matrix elements in the weak-field limit where the AT effect is suppressed, we single out events of pure two-photon coherence occurring owing to constructive quantum interference.

Enhanced cooling of micromechanical oscillator in the atom-assisted optomechanical cavity

We investigate the two-mode optomechanical cavity coupled with the three-level cascade atom. We propose a scheme to enhance the cooling of optomechanical oscillator by introducing atomic medium. Our results show that the existence of the atom can lead to a lower effective temperature of mechanical oscillator comparing to the case without atom. The coherence of the injected atomic affects the population of the photon, which can lead to the change in the radiation pressure on the movable mirror. We also show that the cooling of the mechanical oscillator is affected by initial state of inserting atom.

Spatial Four Wave Mixing, Probe Images, and Fluorescence Signals in Dressed Three-Level System

We investigate the spatial images of the probe, generated four wave mixing (FWM) signal and the accompanying fluorescence spectrum signal simultaneously in FWM process in a cascade three-level atom...

Quantum entanglement of the binomial field interacting with a cascade three-level atom beyond the rotating wave approximation

In this paper, the quantum entanglement between a single mode binomial field and a cascade three-level atom is calculated mechanically without the rotating wave approximation. The numerical results indicate that the quantum entanglement at the first few periods is reduced notably due to the fact that the atom is initially in the superposition state. With increasing field parameter η, the period of the entanglement evolution becomes obvious and the quantum decoherence phenomenon emerges in a short time.

Entanglement of nanomechanical oscillators and two-mode fields induced by atomic coherence

We propose a scheme via three-level cascade atoms to entangle two optomechanical oscillators as well as two-mode fields. We show that two movable mirrors and two-mode fields can be entangled even for bad cavity limit. We also study entanglement of the output two-mode fields in frequency domain. The results show that the frequency of the mirror oscillation and the injected atomic coherence affect the output entanglement of the two-mode fields.

Interference between competing pathways in the interaction of three-level ladder atoms and radiation

In this paper we explore the physical origin of the transparency induced in absorbing three-level cascade atoms by the simultaneous interplay of two coherent beams of light. By utilizing the scattering technique we offer what we believe is a very convincing physical evidence for the existence, or for the absence, of quantum interference effects in the two considered ladder systems. Bare and dressed states pictures are adopted in two different field regimes when applicable. The conclusions are drawn based on the existence of different excitation pathways and their relative orders of magnitudes. The presented study includes a distinction between the Autler–Townes (AT) and electromagnetically induced transparency (EIT) phenomena.

ENTANGLEMENT CONTROLLING OF A THREE-LEVEL CASCADE ATOM INTERACTING WITH A TIME-DEPENDENT COHERENT FIELD

The interaction between a three-level cascade atom and an initial coherent field with a time-varying frequency has been investigated, including the dynamic behavior of the atomic level occupation probabilities and the entanglement between the atom and the field. The frequency of the field is modulated in the forms of sine and rectangle. It is found that the field-frequency variation has a great influence on the properties of the generalized Jaynes-Cummings model. Appropriate frequency modulation can enhance and stabilize the degree of entanglement between the atom and the field.

Enhanced entanglement by collective interactions of three-level atoms in a cavity

In this paper, we investigate the generation of entangled light via collectively interacting three-level cascade atoms in a two-mode cavity. It is found that the atomic collectivity can effectively increase the strength of the frequency down-conversion process in the system and lead to the significant enhancement of the entanglement between the two cavity modes, in comparison to the case of independent atoms.

Evolution of atom entropy in a moving cascade three-level atom in a two-photon process

The entropy evolution properties of field (atom) in a moving cascade three-level atom interacting with a single-mode field are studied through two photon transitions. When the atom is initially in coherent state, the influences of the atomic motion, the field-mode structure parameter and the initial average photon number on the evolution of the entropy are discussed. The results show that the entropy evolution period of the field is dependent of the atomic motion and the field-mode structure parameter. However, the parameter of the initial average photon number will neither lengthen nor shorten the entropy evolution period of the field, but the numerical values of maximum and sub-minimum of entropy will be affected by it.

Teleportation of a bipartite entangled coherent state via cavity QED

Based on the atom-cavity-field interaction, this paper proposes a scheme for the teleportation of a bipartite entangled coherent state (ECS) with high fidelity as long as |α| is not too small. In this proposal, only four cavities and a three-level cascade atom are needed. The fidelity of the ECS is calculated and analysed in detail.

Localization of a Three-Level Cascade Atom via ResonantAbsorption

We show that it is possible to localize a three-level cascade atom under theresonance condition when it passes through a standing-wave field. Thelocalization peaks appear at the nodes of the standing-wave field, thedetecting probability is 50% in the subwavelength domain, and the peaksare narrower on the resonance than the off-resonance. The absorption isthe same as that in the usual two-level medium at the nodes and isgreatly suppressed outside the nodes due to the Autler–Townessplitting. This is in sharp contrast to the lambda scheme, in which thelocalization is impossible under the same resonance condition due to thedepletion of population of the initial state by the probe field at thenodes and the electromagnetically induced transparency outside thenodes.