Studies of quantum spin chain dynamics and their potential applications in quantum information

Abstract

Quantum information processing has been the subject of intense research due to its potential applications in computation, communication, and fundamental science. In this regard, numerous physical systems like superconducting circuits, quantum dots etc., have been proposed for realizing quantum processors. In spite of the wide variety of the proposals, there exist a few classes of models that may describe the relevant properties of most such devices. One dimensional quantum spin systems called spin chains is one such class. In this thesis, we investigate the dynamics of spin chains from the perspective of quantum information processing. In particular, we consider three specific applications: quantum state transfer, quantum state amplification and quantum state engineering. First, we study the feasibility of using spin chain as a quantum wire. We propose an adiabatic scheme for robust high fidelity quantum transport. The scheme is studied both numerically and theoretically with a detailed discussion of its advantages. Next, by extending the ideas of this transport scheme, we propose a scheme for controlled measurement of a single spin state. We investigate the scheme in detail both in idealistic and realistic models. In addition, using the correspondence between spin chain and a well studied quantum dynamical system, we have come up with a scheme to engineer arbitrary quasimomentum states of spin chains. The scheme can also be used to efficiently generate entangled W states in spin chains. In addition to these applications, we have investigated the dynamics of spin chains for gaining insights into intriguing properties of quantum many-body systems. Along this line, we introduce a phase space based complexity measure to characterize the complex dynamics of a quantum many-body system. The use of this measure is investigated in a spin chain model. Furthermore, we have investigated the interplay between non-integrability and disorder in the quantum many-body dynamics of spin chains.