Response of entanglement to annealed vis-à-vis quenched disorder in quantum spin models

¹ Department of Applied Mathematics, University of Calcutta - 92 A.P.C. Road, Kolkata 700 009, India
² Harish-Chandra Research Institute, HBNI - Chhatnag Road, Jhunsi, Allahabad 211 019, India
³ Racah Institute of Physics, The Hebrew University of Jerusalem - Jerusalem 91 904, Givat Ram, Israel
⁴ Instytut Fizyki im. Mariana Smoluchowskiego, Uniwersytet Jagielloński - łojasiewicza 11, 30-348 Kraków, Poland
⁵ Institute of Physics, Polish Academy of Sciences - Aleja Lotników 32/46, PL-02668 Warsaw, Poland
⁶ ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology - Av. Carl Friedrich Gauss 3, 08860 Castelldefels (Barcelona), Spain

Received: 23 December 2018
Accepted: 24 July 2019

Abstract

We investigate bipartite entanglement in random quantum XY models at equilibrium. Depending on the intrinsic time scales associated with equilibration of the random parameters and measurements associated with observation of the system, we consider two distinct kinds of disorder, namely annealed and quenched. We conduct a comparative study of the effects of disorder on nearest-neighbor entanglement, when the nature of randomness changes from being annealed to quenched. We find that entanglement properties of the annealed and quenched systems are drastically different from each other. This is realized by identifying the regions of parameter space in which the nearest-neighbor state is entangled, and the regions where a disorder-induced enhancement of entanglement —order-from-disorder— is obtained. We also analyze the response of the quantum phase transition point of the ordered system with the infusion of disorder.