Constructive interference between disordered couplings enhances multiparty entanglement in quantum Heisenberg spin glass models. (24th August 2016)

• Record Type: Journal Article
• Authors: Mishra, Utkarsh; Rakshit, Debraj; Prabhu, R; Sen(De), Aditi; Sen, Ujjwal
• Is Part Of: New journal of physics. Volume 18:Number 8(2016:Aug.)
• Publication Date: 2016-08-24
• Subjects: multiparty entanglement -- quantum spin models -- disordered systems -- constructive interference -- disorder induced enhancement -- heisenberg spin model; Physics -- Periodicals; Physics; Periodicals; 530.05
• DOI: 10.1088/1367-2630/18/8/083044
• Languages: English
• ISSNs: 1367-2630

Abstract

Abstract: Disordered systems form one of the centrestages of research in many body sciences and lead to a plethora of interesting phenomena and applications. A paradigmatic disordered system consists of a one-dimensional array of quantum spin-1/2 particles, governed by the Heisenberg spin glass Hamiltonian with natural or engineered quenched disordered couplings in an external magnetic field. These systems allow disorder-induced enhancement for bipartite and multipartite observables. Here we show that simultaneous application of independent quenched disorders results in disorder-induced enhancement, while the same is absent with individual application of the same disorders. We term the phenomenon as constructive interference and the corresponding parameter stretches as the Venus regions. Interestingly, it has only been observed for multiparty entanglement and is absent for the single- and two-party physical quantities. General Scientific Summary for 'Constructive Interference Between Disordered Couplings Enhances Multiparty Entanglement in Quantum Heisenberg Spin Glass Models': Introduction and background Disordered systems form one of the center-stages of research in many body sciences and lead to a plethora of interesting phenomena and applications. Presence of disorder may lead to nontrivial and counterintuitive properties as compared to their homogeneous counterparts. Prominent examples are novel quantum phases, localization, high-Tc superconductivity and disorder-induced ordering. In this work, we consider paradigmatic disordered systems consisting of a one-dimensional array of quantum spin-1/2 particles, governed by quenched disordered quantum Heisenberg Hamiltonians in external magnetic fields. The primary goal of this work is to understand the bi- and multi-partite quantum entanglement due the interplay of planer and azimuthal couplings when disorder is present in either one of them or both of them. Main results We have examined the behavior of magnetization, two-party classical as well as quantum correlations, and multipartite entanglement for the ground states of quenched disordered quantum Heisenberg spin systems for sizes ranging from five to twenty quantum spin-1/2 particles. The quenched disorder is present in the planar, or the azimuthal couplings, or in both. Our main results are the following. Firstly, in presence of the impurities in the couplings, there exist different parameter regions for different physical quantities, which show disorder-induced enhancement. We identify the parameter stretches where the phenomenon of disorder-induced enhancement corresponding to the quantities under investigation occurs for different possible cases, viz., when disorder is present in either of the interaction terms or disorder is present in both the interaction terms. Secondly, we ask a rather radical question: Is it possible to have disorder-induced enhancement of a physical quantity by the insertion of two types of disorder in a single system, while the disorders when present in the individual interaction terms do not provide any increment? We answer the question in the affirmative provided the external field strength is greater than a cut-off value. We term the phenomenon as "constructive interference" and the corresponding parameter stretches as the "Venus" regions. Interestingly, it has only been observed for multiparty entanglement and is absent for the single- and two-party physical quantities. Wider implications Firstly, the seemingly counterintuitive nature of constructive interference for a physical quantity leads us to believe that it can have implications in fundamental and application regimes. Moreover, multiparty quantum information processing tasks typically have origins in the bipartite domain. Instances where the converse occurs are few and far between, and indicate important diversions from the usual track. Secondly, a detailed knowledge on the effect of disorder on quantum correlations is highly desirable in order to assume perfect control over quantum technologies based on quantum spin magnetic systems. Thirdly, it is interesting to think about possible connections of disorder-induced enhancement with other interesting quantum phenomena such as many-body localization.