In this paper, we investigate the effects of incoherent pumping on quantum correlations in a Λ -type atomic system driven by coherent and incoherent fields simultaneously. With the adiabatic elimination treatment, we show that the stable “one-way” Einstein–Podolsky–Rosen (EPR) steering is generated without the requirement of good cavity limitation. More interestingly, the asymmetrical EPR steering is simply controlled by the polarized angle of the incoherent field. The internal mechanisms can be understood based on dressed-state representation, in which the population differences are strongly modified by the quantum interference from incoherent pumping. The phase-sensitive quantum correlations in the present scheme may find potential applications in quantum information processing.
In this paper, we investigate the effects of incoherent pumping on quantum correlations in a Λ -type atomic system driven by coherent and incoherent fields simultaneously. With the adiabatic elimination treatment, we show that the stable “one-way” Einstein–Podolsky–Rosen (EPR) steering is generated without the requirement of good cavity limitation. More interestingly, the asymmetrical EPR steering is simply controlled by the polarized angle of the incoherent field. The internal mechanisms can be understood based on dressed-state representation, in which the population differences are strongly modified by the quantum interference from incoherent pumping. The phase-sensitive quantum correlations in the present scheme may find potential applications in quantum information processing.
Abstract We investigate the Einstein–Podolsky–Rosen (EPR) steering of two cavity modes generated via four-wave mixing processes. For a three-level V-type configuration, a strong coherent field as a dressing field couples the atoms, and a weak coherent field as a control filed resonantly couples one dressed state to the auxiliary state. By using the approach of dressed states and Bogoliubov modes, we find that only one Bogoliubov mode is mediated into the interaction with the dressed atoms, and the other one is decoupled. Due to the presence of the coherent control filed, the channel for dressed state population transfer is established, which plays a key role in the generation of the asymmetric EPR steering of two cavity fields. It is shown that the one-way EPR steering can be manipulated by the Rabi frequencies of the control field and the cooperativity parameters.
We explore the asymmetric Einstein-Podolsky-Rosen (EPR) steering of field modes via atomic coherent effects. A resonant four-level system in double-cascade configuration is under our consideration, where the atoms are excited by the applied fields from one cascade channel and two cavity modes are generated from the other cascade transition. The results show two cavity modes are suitable for achieving the steady-state one-way EPR steering. We analyze the physics in terms of the dressed-atom Bogoliubov-field-mode approach. It is found that one of two Bogoliubov modes is mediated by the resonant coupling of the dressed atoms and the other is decoupled from them. This leads to the so-called one-channel dissipation, by which the dressed atoms absorb the average excitations from one transformed mode and then two original modes are pulled into the asymmetric correlation. Remarkably, the present scheme is focused on the full-resonant interaction not only between the classical fields, the cavity modes and the bare atoms, but also between the Bogoliubov modes and dressed atoms, which will induce the one-way steering simply via adjusting the intensity of an external field. Furthermore, the EPR steering could occur between the field modes with the large frequency difference, such as optical and microwave fields, which is more useful for the practical quantum communication. Based on the one-channel dissipation, the obtainable one-way EPR steering is rather against the dynamic fluctuations and is regardless of the initial state.
It is shown that the dephasing rates are usually harmful for quantum correlations in various systems. Nevertheless, we explore that the dephasing rates in the coupled quantum wells (QWs), as a major contribution of the decay processes, can assist to generate one-way Einstein-Podolsky-Rosen (EPR) steering. By applying two strong fields to drive two dipole-allowed transitions while the other transitions are coupled with two quantized modes, the asymmetric EPR steering is possible to obtain at steady state through a single-pathway dissipation in the three-well system. According to dressed-state and Bogoliubov mode transformation, we find that the dephasing rates play a role in modifying the dressed-state populations and the dissipation rate through multiple quantum interference mechanisms. The positive effect of the dephasing rates from a nanostructure on quantum correlation is expected to find potential applications in quantum information processing.
Abstract We show that thermal noise could play a positive role in generating one-way Einstein–Podolsky–Rosen (EPR) steering of two cavity fields dispersively interacting with a single four-level atom, each of which is independently coupled to a thermal reservoir. In the low- Q and weak Raman transition regimes, two output fields exhibit asymmetric EPR steering and the steering direction could be easily controlled by adjusting the mean photon numbers of the thermal reservoirs and the decay rates of cavities. Striking features are present in our scheme. First, one-way EPR steering is achieved by using the couplings of the cavities with the heat baths, which sheds light on the quantum state manipulation in the presence of decoherence. Second, the obtainable EPR steering occurs between the cavity fields in the low- Q regime, which relaxes the constraints on the use of good cavities and so makes our scheme more practical. Third, the correlation properties of the output modes are considered, which can be measured more conveniently and will be more applicable to implement a range of quantum information processing.
Abstract We show that thermal noise could play a positive role in generating one-way Einstein–Podolsky–Rosen (EPR) steering of two cavity fields dispersively interacting with a single four-level atom, each of which is independently coupled to a thermal reservoir. In the low- Q and weak Raman transition regimes, two output fields exhibit asymmetric EPR steering and the steering direction could be easily controlled by adjusting the mean photon numbers of the thermal reservoirs and the decay rates of cavities. Striking features are present in our scheme. First, one-way EPR steering is achieved by using the couplings of the cavities with the heat baths, which sheds light on the quantum state manipulation in the presence of decoherence. Second, the obtainable EPR steering occurs between the cavity fields in the low- Q regime, which relaxes the constraints on the use of good cavities and so makes our scheme more practical. Third, the correlation properties of the output modes are considered, which can be measured more conveniently and will be more applicable to implement a range of quantum information processing.
Einstein-Podolsky-Rosen (EPR) steering, that is, an intermediate form of quantum correlations with asymmetry in between entanglement and Bell nonlocality, plays an essential role in quantum information processing, such as one-sided device-independent quantum cryptography tasks. Here we theoretically study the direct generation of EPR steering in ${\ensuremath{\chi}}^{(2)}$ nonlinear optical processes with cascaded crystals in a self-phase-locked optical parametric oscillator. Based on a standard linearization method, we analyze different conditions for generating EPR steering in Gaussian states with vanishing or nonzero mean fields, and also show bistable regions for different types of EPR steering. In particular, such system can intrinsically generate asymmetry one-way EPR steering, without introducing any postoperation. Our results suggest that the self-phase-locked optical parametric oscillator is a good candidate to generate different types of EPR steering at will by varying the cavity detunings, photon loss, or input pump power.