We analyze quantum correlations in four-wave mixing in three-level ⌳ and V atomic systems by using dressed atomic states and squeeze-transformed cavity modes. Two dissipation channels are identified, through which the dressed atoms simultaneously absorb in the excitations from the pair of squeeze-transformed modes. It is in the presence of two channels that the entanglement is greatly enhanced and the best achievable state approaches the original Einstein-Podolsky-Rosen entangled state. This scheme is applicable in the optical regime where atomic spontaneous emission has to be taken into account, unlike the two-step atomic reservoir engineering scheme, which is limited to the microwave regime.

Electromagnetically induced phase grating is theoretically investigated in the driven two-level quantum dot exciton system at the presence of the exciton-phonon interactions. Due to the phonon-induced coherent population oscillation, the dispersion and absorption spectra are sharply changed and the phase modulation is enhanced via the high refractive index with nearly-vanishing absorption, which could effectively diffract a weak probe light into the first-order direction with the help of a standing-wave control field. Moreover, the diffraction efficiency of the grating can be easily manipulated by controlling the Huang-Rhys factor representing the exciton-phonon coupling, the intensity and detuning of the control field, and the detuning of the probe field. The scheme we present has potential applications in the photon devices for optical-switching and optical-imaging in the micro-nano solid-state system.

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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.

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.