Exceptional Points from the Hamiltonian of a hybrid physical system: Squeezing and anti-Squeezing
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THE EUROPEAN PHYSICAL JOURNAL D
Regular Article
Exceptional Points from the Hamiltonian of a hybrid physical system: Squeezing and anti-Squeezing? Romina Ram´ırez1 , Marta Reboiro2,a , and Diego Tielas3 1 2 3
Department of Mathematics, National University of La Plata, La Plata, Argentina IFLP, CONICET-Department of Physics, National University of La Plata, La Plata, Argentina IFLP, CONICET-Faculty of Engineering, National University of La Plata, La Plata, Argentina Received 15 April 2020 / Received in final form 3 July 2020 / Accepted 3 August 2020 Published online 22 September 2020 c EDP Sciences / Societ`
a Italiana di Fisica / Springer-Verlag GmbH Germany, part of Springer Nature, 2020 Abstract. We study the appearance of Exceptional Points in a hybrid system composed of a superconducting flux-qubit and an ensemble of nitrogen-vacancy colour centres in diamond. We discuss the possibility of controlling the generation of Exceptional Points, by the analysis of the model space parameters. One of the characteristic features of the presence of Exceptional Points, is the departure from the exponential decay behaviour of the observables as a function of time. We study the time evolution of different initial states, in the presence of the hybrid system, by computing the reduced density matrix of each subsystem. We present the results we have obtained for the steady behaviour of different observables. We analyse the appearance of Squeezed Spin States and anti-Squeezed Spin States.
1 Introduction Quantum information processing [1,2] can involve the interplay of atoms in optical traps [3,4], superconducting circuits [5,6], nuclear spins [7] and defects in a crystal lattice [8], among other physical components. Usually, quantum coherence of these localized systems is degraded by the interaction with the environment [9,10]. It can be differentiated two to include the interaction with the environment [11,12]. In one case, the environment consists of microscopic degrees of freedom and it is described by an energy continuum [13–15]. While, in the other case, it can be modelled by some macroscopic approximation of these microscopic degrees of freedom [16–22]. In a recent work [12], these two types of interactions were compared and combined to describe the essentials of a tight-binding model, which could be implemented by an optical lattice with a defect scattering centre. The authors of [12] have characterized in detail the spectrum of the system, both the discrete and the scattering states, in terms of the coupling parameters. In the last years, in different pioneering experiments [18–20,23–26], as a result of the coupling of the physical system with its environment, the occurrence of dynamical breaking of symmetry has been observed. As a function of time, the relevant physical observables obey an oscillatory pattern in a region of the space of control parameters and ?
Supplementary Material in the form of one pdf file available from the Journal web page at https://doi.org/10.1140/epjd/e2020-10218-1 a e-mail: reboiro@fisi
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