Characterization and control of quantum spin chains and rings

Abstract-Propagation of information encoded in spin degrees of freedom through networks of coupled spins enables important applications in spintronics and quantum information processing. We study control of information propagation in networks of spin-1 2 particles with uniform nearest neighbor couplings forming a ring with a single excitation in the network as simple prototype of a router for spin-based information. Specifically optimizing spatially distributed potentials, which remain constant during information transfer, simplifies the implementation of the routing scheme. However, the limited degrees of freedom makes finding a control that maximizes the transfer probability in a short time difficult. We show that the structure of the eigenvalues and eigenvectors must fulfill a specific condition to be able to maximize the transfer fidelity, and demonstrate that a specific choice among the many potential structures that fulfill this condition significantly improves the solutions found by optimal control. I. INTRODUCTIONEncoding information spin degrees of freedom has the potential to revolutionize information technology via the development of novel spintronic devices and possible future quantum information processors [1], [2]. Utilizing information encoded in spin degrees of freedom, however, requires efficient, controlled on-chip transfer of spin-based information. In some types of spintronic devices, spin degrees of freedom are used in addition to motional degrees of freedom of electrons, and information encoded in the spin degrees of freedom can be transferred using conventional currents. In principle, however, information stored in spin states can propagate through a network of coupled spins without charge transport. As propagation of spin-based information is governed by quantum-mechanics and the Schrödinger equation, however, excitations in a spin network propagate, disperse and refocus in a wave-like manner, and controlling information transport is thus a quantum control problem. Without any means to control the propagation of spin-based information in such networks information transport can be slow and inefficient. Control can be utilized to optimize transport in terms of maximizing transfer efficiency and speed [3], [4]. Here, we consider how to control information propagation in a network of spins by optimizing spatially distributed potentials, which remain constant during the evolution, in contrast to dynamic control schemes, which require dynamic modulation or fast switching of the control potentials.

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Characterization and control of quantum spin chains and rings

Cited by 2 publications

References 18 publications

Exploring entropic uncertainty relation in the Heisenberg XX model with inhomogeneous magnetic field

Exploring entropic uncertainty relation in the Heisenberg XX model with inhomogeneous magnetic field

Time optimal information transfer in spintronics networks

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