Resonance fluorescence engineering in hybrid systems consist of biexciton quantum dots and anisotropic metasurfaces.

The resonance fluorescence properties in the steady-state regime are investigated for a driven cascaded exciton-biexciton quantum dot coupled to the two-dimensional black phosphorus metasurfaces. It is shown that for the material parameters under consideration, both the elliptic and hyperbolic dispersion patterns of the surface plasmon modes are achievable according to the variation of the carrier concentration. Further study on the Purcell factor indicates unequal enhancements in the spontaneous decay of the orthogonal in-plane dipoles. Motivated by this intriguing phenomenon, we then investigate the steady-state properties of the driven quantum dot, where the populations of the dressed levels are highly tunable by engineering the anisotropy of the surfaces. As a result, the manipulation of the carrier concentration will lead to strong modifications in the resonance fluorescence. Under certain conditions, one can observe the squeezing of two-mode noise spectra with different resonances and polarizations. Although at the expense of declines in the photon-sideband detunings, it is feasible to enhance the two-mode squeezing by gate doping. Our proposal can be easily extended to other hybrid systems containing anisotropic metasurfaces, which are important for the development of quantum information science.

Self-Adaptive Image Thresholding within Nonextensive Entropy and the Variance of the Gray-Level Distribution.

In order to automatically recognize different kinds of objects from their backgrounds, a self-adaptive segmentation algorithm that can effectively extract the targets from various surroundings is of great importance. Image thresholding is widely adopted in this field because of its simplicity and high efficiency. The entropy-based and variance-based algorithms are two main kinds of image thresholding methods, and have been independently developed for different kinds of images over the years. In this paper, their advantages are combined and a new algorithm is proposed to deal with a more general scope of images, including the long-range correlations among the pixels that can be determined by a nonextensive parameter. In comparison with the other famous entropy-based and variance-based image thresholding algorithms, the new algorithm performs better in terms of correctness and robustness, as quantitatively demonstrated by four quality indices, ME, RAE, MHD, and PSNR. Furthermore, the whole process of the new algorithm has potential application in self-adaptive object recognition.

Spin Isoenergetic Process and the Lindblad Equation.

A general comment is made on the existence of various baths in quantum thermodynamics, and a brief explanation is presented about the concept of weak invariants. Then, the isoenergetic process is studied for a spin in a magnetic field that slowly varies in time. In the Markovian approximation, the corresponding Lindbladian operators are constructed without recourse to detailed information about the coupling of the subsystem with the environment called the energy bath. The entropy production rate under the resulting Lindblad equation is shown to be positive. The leading-order expressions of the power output and work done along the isoenergetic process are obtained.

Comment on "Route from discreteness to the continuum for the Tsallis q-entropy".

Several years ago, it had been discussed that nonlogarithmic entropies, such as the Tsallis q-entropy cannot be applied to systems with continuous variables. Now, in their recent paper [Phys. Rev. E 97, 012104 (2018)10.1103/PhysRevE.97.012104], Oikonomou and Bagci have modified the form of the q-entropy for discrete variables in such a way that its continuum limit exists. Here, it is shown that this modification violates the expandability property of entropy, and their work is actually supporting evidence for the absence of the q-entropy for systems with continuous variables.

Thermostatistic properties of a q-generalized Bose system trapped in an n-dimensional harmonic oscillator potential.

The thermostatistic properties of a q-generalized boson system trapped in an n-dimensional harmonic oscillator potential are studied, based on the generalized statistic distribution derived from Tsallis' entropy. The density of states, total number of particles, critical temperature at which Bose-Einstein condensation occurs, internal energy, and heat capacity at constant volume are derived. The characteristics of Bose-Einstein condensation of the system are discussed in detail. It is found from the results obtained here that the thermostatistic properties of such a system depend closely on parameter q, dimensional number of the space, and frequency of the harmonic oscillator; and the external potential has a great influence on the thermostatistic properties of the system.