Abstract Einstein–Podolsky–Rosen (EPR) steering as a form of quantum correlation lies between entanglement and Bell nonlocality and exhibits an inherent asymmetry between two observers. We study EPR steering of two fields, which are generated via four-wave mixing processes and are entangled with each other due to the dissipation of the atomic reservoir. It is shown that the one-way steering happens from one mode to the other for different cavity decay rates and not too small cooperation parameters. Depending on the adiabatic and nonadiabatic conditions, the one-way steering occurs in a different detuning region when the cooperation parameters are relatively small. An increase in the cooperation parameters leads to an increase both in the parameter region and in the degree for the one-way steering. Finally we generalize the present scheme to the cases of the bright and/or collective fields.
Abstract Einstein–Podolsky–Rosen (EPR) steering as a form of quantum correlation lies between entanglement and Bell nonlocality and exhibits an inherent asymmetry between two observers. We study EPR steering of two fields, which are generated via four-wave mixing processes and are entangled with each other due to the dissipation of the atomic reservoir. It is shown that the one-way steering happens from one mode to the other for different cavity decay rates and not too small cooperation parameters. Depending on the adiabatic and nonadiabatic conditions, the one-way steering occurs in a different detuning region when the cooperation parameters are relatively small. An increase in the cooperation parameters leads to an increase both in the parameter region and in the degree for the one-way steering. Finally we generalize the present scheme to the cases of the bright and/or collective fields.
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.
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.
Einstein-Podolsky-Rosen (EPR) steering exhibits an inherent asymmetric feature that differs from both entanglement and Bell nonlocality, which leads to one-way EPR steering. Although this one-way EPR steering phenomenon has been experimentally observed, the schemes to manipulate the direction of EPR steering have not been investigated thoroughly. In this paper, we propose and experimentally demonstrate three schemes to manipulate the direction of EPR steering, either by varying the noise on one party of a two-mode squeezed state (TMSS) or transmitting the TMSS in a noisy channel. The dependence of the direction of EPR steering on the noise and transmission efficiency in the quantum channel is analyzed. The experimental results show that the direction of EPR steering of the TMSS can be changed in the presented schemes. Our work is helpful in understanding the fundamental asymmetry of quantum nonlocality and has potential applications in future asymmetric 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.
Einstein-Podolsky-Rosen (EPR) steering is a form of quantum correlation and its intrinsic asymmetry makes it distinct from entanglement and Bell nonlocality. We propose here a scheme for realizing one-way Gaussian steering of two electromagnetic fields mediated by a mechanical oscillator. We reveal that the steady-state one-way steering of the intracavity and output fields is obtainable with different cavity losses or strong mechanical damping. The conditions for achieving this asymmetric steering are found, and it shows that the steering is robust against thermal mechanical fluctuations. The present scheme can realize hybrid microwave-optical asymmetric steering by optoelectromechanics. In addition, our results are generic and can also be applied to other three-mode parametrically coupled bosonic systems.