Abstract We examine the quantum steering and coherence for two qubits that are immersed in an isotropic (I) and anisotropic (A) photonic band-gab (PBG) crystal. We show how the steerability and coherence of the qubits’ state depends on the essential parameters of the model and initial state setting of the qubits. We find that the prevention of the amount of quantum steering and coherence can be achieved in the presence of PBG materials by a considerable choice of the system parameters. Furthermore, we show that the quantum steering and coherence can resist the degradation during the dynamics in IPBG more than in APBG according to the same physical conditions. Finally, we illustrate the relationship between the quantum steering and coherence with respect to the system parameters under the decoherence effect. These obtained results reveal that quantum systems in PBG materials are very useful to implement diverse applications of quantum technology with optimal performance.
Abstract We examine the quantum steering and coherence for two qubits that are immersed in an isotropic (I) and anisotropic (A) photonic band-gab (PBG) crystal. We show how the steerability and coherence of the qubits’ state depends on the essential parameters of the model and initial state setting of the qubits. We find that the prevention of the amount of quantum steering and coherence can be achieved in the presence of PBG materials by a considerable choice of the system parameters. Furthermore, we show that the quantum steering and coherence can resist the degradation during the dynamics in IPBG more than in APBG according to the same physical conditions. Finally, we illustrate the relationship between the quantum steering and coherence with respect to the system parameters under the decoherence effect. These obtained results reveal that quantum systems in PBG materials are very useful to implement diverse applications of quantum technology with optimal performance.
By considering two kinds of non-Markovian (NM) environments, the dynamical behavior of quantum steering, Bell nonlocality and coherence of a system of two atoms initially immersed in a vacuum has been studied. In this context, the cases of a cavity little off-resonance with the atomic transition frequency and non-perfect photonic band-gap (NPPBG) has been considered. The control and preservation of the quantumness measures is discussed in terms of the physical parameters. Furthermore, the situations for which the atoms state is steerable with the presence of Bell nonlocality and coherence has been illustrated. Finally, the monotonic dependence among the quantumness measures is displayed with respect to the model parameters.
The quantum Fisher information (QFI) of a two-level atom in an anisotropic and isotropic photonic band-gap (PBG) crystal has been studied without Born or Markovian approximation. We show that the precision of the parameter estimation for the two-level atom in the photonic crystal is greatly different from that of a two-level atom in vacuum or that subjected to the usual non-Markovian reservoir. The phenomenon shows that the QFI, namely, the precision of estimation, changes dramatically with the environment structure. The results also show that, for PBG materials, environmentally high values of QFI trapping can be achieved and thus prevention of QFI sudden drop occurs, which greatly enhances the coherence and increases the precision of estimation. Moreover, the QFI in the isotropic PBG is more easily preserved than that of the anisotropic PBG under the same condition. These features make the atom system in PBG materials a good candidate for implementation of different schemes of quantum optics and information with high precision.
By using the Born Markovian master equation, we study the relationship among the Einstein-Podolsky-Rosen (EPR) steering, Bell nonlocality, and quantum entanglement of entangled coherent states (ECSs) under decoherence. We illustrate the dynamical behavior of the three types of correlations for various optical field strength regimes. In general, we find that correlation measurements begin at their maximum and decline over time. We find that quantum steering and nonlocality behave similarly in terms of photon number during dynamics. Furthermore, we discover that ECSs with steerability can violate the Bell inequality, and that not every ECS with Bell nonlocality is steerable. In the current work, without the memory stored in the environment, some of the initial states with maximal values of quantum steering, Bell nonlocality, and entanglement can provide a delayed loss of that value during temporal evolution, which is of interest to the current study.
A comparative study of a qutrit (three-level atomic system) coupled to a classical field in a typical Markovian reservoir (free space) and in a photonic-band-gap (PBG) crystal is carried out. The aim of the study is to assess the collective impact of a structured environment and classical control of the system on the dynamics of quantum coherence, non-Markovianity, and estimation of parameters that are initially encoded in the atomic state. We show that the constructive interplay of PBG material as a medium and a classical driving field as a part of the system results in a significant enhancement of all the quantum traits of interest, compared to the case when the driven qutrit is in a Markovian environment. Our results supply insights for preserving and enhancing quantum features in qutrit systems, which are promising alternative candidates to be used in quantum processors instead of qubits.
Collective Einstein-Podolsky-Rosen (EPR) steering is a unique multipartite resource that enables the realization of more secure communication protocols. However, due to the lack of suitable experimental criteria, research on collective EPR steering has so far been limited to continuous variable systems. Here, we employ the coherence-based collective EPR steering criteria proposed by Mondal et al. [Phys. Rev. A 99, 012312 (2019)] and develop a semidefinite programming method to find the optimal measurement settings. Experimentally, we take the three-qubit generalized Greenberger-Horne-Zeilinger states and generalized W states as examples, demonstrating that collective EPR steering can be observed by detecting the average l1 norm of coherence of the steered subsystem. We also explored the effect of measurement settings on complementarity relations between different collective steering criteria, and established a connection between collective steering and coherence complementarity. Our paper fills a gap in the verification of collective steerability in discrete variable systems and reveals a profound connection between EPR steering and quantum coherence.
Occupying a position between entanglement and Bell nonlocality, Einstein-Podolsky-Rosen (EPR) steering has attracted increasing attention in recent years. Many criteria have been proposed and experimentally implemented to characterize EPR-steering. Nevertheless, only a few results are available to quantify steerability using analytical results. In this work, we propose a method for quantifying the steerability in two-qubit quantum states in the two-setting EPR-steering scenario, using the connection between joint measurability and steerability. We derive an analytical formula for the steerability of a class of X-states. The sufficient and necessary conditions for two-setting EPR-steering are presented. Based on these results, a class of asymmetric states, namely, one-way steerable states, are obtained.