Composite bosons made of two bosonic constituents exhibit deviations from ideal bosonic behavior due to their substructure. This deviation is reflected by the normalization ratio of the quantum state of N composites. We find a set of saturable, efficiently evaluable bounds for this indicator, which quantifies the bosonic behavior of composites via the entanglement of their constituents. We predict an abrupt transition between ordinary and exaggerated bosonic behavior in a condensate of two-boson composites.
Linear media are predicted to exist whose relative permiability is an operator in the space of quantum states of light. Such media are characterized by a photon statistics--dependent refractive index. This indicates a new type of optical dispersion -- the photon statistics dispersion. Interaction of quantum light with such media modifies the photon number distribution and, in particular, the degree of coherence of light. An excitonic composite -- a collection of noninteracting quantum dots -- is considered as a realization of the medium with the photon statistics dispersion. Expressions are derived for generalized plane waves in an excitonic composite and input--output relations for a planar layer of the material. Transformation rules for different photon initial states are analyzed. Utilization of the photon statistics dispersion in potential quantum--optical devices is discussed.
Gaussian boson sampling is a promising scheme for demonstrating a quantum computational advantage using photonic states that are accessible in a laboratory and, thus, offer scalable sources of quantum light. In this contribution, we study two-point photon-number correlation functions to gain insight into the interference of Gaussian states in optical networks. We investigate the characteristic features of statistical signatures which enable us to distinguish classical from quantum interference. In contrast to the typical implementation of boson sampling, we find additional contributions to the correlators under study which stem from the phase dependence of Gaussian states and which are not observable when Fock states interfere. Using the first three moments, we formulate the tools required to experimentally observe signatures of quantum interference of Gaussian states using two outputs only. By considering the current architectural limitations in realistic experiments, we further show that a statistically significant discrimination between quantum and classical interference is possible even in the presence of loss, noise, and a finite photon-number resolution. Therefore, we formulate and apply a theoretical framework to benchmark the quantum features of Gaussian boson sampling under realistic conditions.
We envision that dispersion between two polymeric materials on mesoscales would create new composites with properties that are much more superior to the components alone. Here we elucidate the dispersion between two of most abundant natural polysaccharides, starch and chitosan, which form mesoscale composites that may promise many applications. By using X-ray microscopic imaging, small-angle X-ray scattering, and differential scanning calorimetry, we were able to characterize the interactions of chitosan and starch in the mesoscale composites. The morphology of the composite is far more complex from the simple mixture of starch granules with a nominal size of a few micrometers and chitosan microbundles of tens and hundreds of micrometers. This unique morphology can only be explained by the enhanced miscibility of chitosan in a starch granular matrix. It is evidenced that there is a possible ionic interaction between the amino group in chitosan and the hydroxyl groups in starch granules. Despite the limited solubility of chitosan in water, this ionic interaction allows for the disassembly of chitosan microbundles within the starch suspension. The result is a chemically stronger and more stable granular composite formed by two biocompatible and biodegradable polysaccharide polymers. The mechanism of chitosan to disperse throughout starch granules has implications for the application of chitosan in water and other solvents.
We study the necessary conditions for bosons composed of two distinguishable fermions to exhibit bosonic-like behaviour. We base our analysis on tools of quantum information theory such as entanglement and the majorization criterion for probability distributions. In particular we scrutinize a recent interesting hypothesis by C. K. Law in the Ref. Phys. Rev. A 71, 034306 (2005) that suggests that the amount of entanglement between the constituent fermions is related to the bosonic properties of the composite boson. We show that a large amount of entanglement does not necessarily imply a good boson-like behaviour by constructing an explicit counterexample. Moreover, we identify more precisely the role entanglement may play in this situation.
We introduce the Rydberg Composite, a new class of Rydberg matter where a single Rydberg atom is interfaced with a dense environment of neutral ground state atoms. The properties of the Composite depend on both the Rydberg excitation, which provides the gross energetic and spatial scales, and on the distribution of ground state atoms within the volume of the Rydberg wave function, which sculpt the electronic states. The latter range from the trilobites, for small numbers of scatterers, to delocalized and chaotic eigenstates for disordered scatterer arrays, culminating in the dense scatterer limit in symmetry-dominated wave functions which promise good control in future experiments. We characterize these scenarios with different theoretical methods, enabling us to obtain scaling behavior for the regular spectrum and measures of chaos and delocalization in the disordered regime. Thus, we obtain a systematic description of the Composite states. The 2D monolayer Composite possesses the richest spectrum with an intricate band structure in the limit of homogeneous scatterers.