PACS. 03.65.Ud -Entanglement and quantum nonlocality. PACS. 73.43.Nq -Quantum phase transitions. PACS. 75.10.-b -General theory and models of magnetic ordering.Abstract. -We show that the quantum phase transition arising in a standard radiationmatter model (Dicke model) belongs to the same universality class as the infinitely-coordinated, transverse field XY model. The effective qubit-qubit exchange interaction is shown to be proportional to the square of the qubit-radiation coupling. A universal finite-size scaling is derived for the corresponding two-qubit entanglement (concurrence) and a size-consistent effective Hamiltonian is proposed for the qubit subsystem.Quantum phase transitions (QPTs) are associated with a dramatic change in the physical properties of a system at zero temperature when a parameter varies around its critical value. It is well-known that very different systems can exhibit similar behavior in this critical regime, giving rise to the concept of universality. Enlarging a given universality class by the addition of systems from very different areas of physics, is a very important step toward unifying our understanding of the basic physics underlying apparently disconnected complex phenomena. Recently there have been studies of light-controlled condensed matter systems displaying QPTs with atoms in extreme one-dimensional confinements [1], ions driven by properly tuned and pulsed light [2] and fermionic atoms in optical superlattices [3]. Fully quantum mechanical models of radiation-matter systems are also being considered, and are important for several reasons: Scalable and distributed quantum information processing (QIP) devices will demand the integration of matter quantum bits (qubits) such as atoms, trapped ions, semiconductor quantum dots or SQUIDs with photons. In addition, the capability of photons to control and modify the coupling between physically distant qubits makes them appropriate for manipulating and transferring quantum information.
Bose-Einstein condensates subject to short pulses ͑"kicks"͒ from standing waves of light represent a nonlinear analog of the well-known chaos paradigm, the quantum kicked rotor. Previous studies of the onset of dynamical instability ͑i.e., exponential proliferation of noncondensate particles͒ suggested that the transition to instability might be associated with a transition to chaos. Here we conclude instead that instability is due to resonant driving of Bogoliubov modes. We investigate the Bogoliubov spectrum for both the quantum kicked rotor ͑QKR͒ and a variant, the double kicked rotor ͑QKR-2͒. We present an analytical model, valid in the limit of weak impulses which correctly gives the scaling properties of the resonances and yields good agreement with mean-field numerics.
We present an analysis of the entangling quantum kicked top focusing on the few qubit case and the initial condition dependence of the time-averaged entanglement SQ for spin-coherent states. We show a very strong connection between the classical phase space and the initial condition dependence of SQ even for the extreme case of two spin-1/2 qubits. This correlation is not related directly to chaos in the classical dynamics. We introduce a measure of the behavior of a classical trajectory which correlates far better with the entanglement and show that the maps of classical and quantum initial-condition dependence are both organized around the symmetry points of the Hamiltonian. We also show clear (quasi-)periodicity in entanglement as a function of number of kicks and of kick strength.
The interdependence between long range correlations and topological signatures in fermionic arrays is examined. End-to-end correlations, in particular those accounting for the hopping between the chain edges, maintain a characteristic pattern in the presence of delocalized excitations. This feature can be used as an operational criterion to identify Majorana fermions in one-dimensional systems. The study discusses how to obtain the chain eigenstates in tensor-state representation as well as the correlations. Outstandingly, the final result can be written as a simple analytical expression that underlines the link with the system's topological phases.
We study the ground state as well as the dynamics of chains of bosons with local repulsive interactions and nearest-neighbour exchange using numerical techniques based on density matrix decimation. We explore the development of entanglement between the terminal sites of such chains as mechanisms are invoked to concentrate population in these sites. We find that long-range entanglement in the ground state emerges as a result of transfer taking place across the length of the whole chain in systems with appropriate hopping coefficients. Additionally, we find appropriate perturbations to increase the entanglement between the end sites above their ground state values.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.