QMHP:: Decoherence, dissipation, entanglement and control in nanostructures.

Purdue University, West Lafayette IN

Investigators

Abstract

QMHP: Decoherence, dissipation, entanglement and control in nanostructures. Over the past decade, electronic devices have been getting smaller and smaller, driving the progress of technology. Smaller devices are desirable for improving computer speed and the complexity of computer chips. The possibility of continuing this trend is limited because technology is already close to reaching the atomic level. Remarkably, in this limit, different rules of electron behavior, particularly quantum phenomena, become important. Tapping the laws of quantum mechanics presents the opportunity of using quantum-mechanical coherence, interference of electronic waves, and entanglement ? linking of quantum mechanical objects so that one object cannot be described without knowledge of its counterpart - for developing a new generation of nanodevices. A fundamental challenge is the understanding and realization of quantum phenomena in devices which function under voltage, i.e., in non-equilibrium conditions, and in the presence of disorder and fluctuations due to impurity atoms that play an important role in supplying charge carriers and defining electric and magnetic properties. Quantum phenomena are limited by loss of coherence (decoherence), and it is necessary to identify mechanisms of losses and to find the means to control them. Decoherence will define dissipation per bit of information in future information technology systems. Scientific efforts directed at a theoretical understanding of decoherence and dissipation will be focused on three interconnected projects: 1) absorption of power and Rabi oscillations (cyclic quantum behavior) in artificial nanoscale atoms - quantum dots, 2) loss of coherence by spin (intrinsic quantum angular momentum) and charge in silicon quantum dots, 3) theory of coherence and transport in magnetic semiconductor nanostructures, which may combine magnetic memory and electronic functionalities in single devices. Intellectual merit: The proposed research holds a promise to elucidate specific mechanisms of decoherence in quantum devices and to devise methods to control decoherence and dissipation. Though not the sole focus of the work the results may benefit quantum computing research. The proposed approach promises to overcome formal challenges of treating time-dependent quantum behavior in the presence of voltage, taking into account strong correlations and entanglement effects. The expected analytical results will have a potential to affect the future modeling of quantum devices. Broader impacts: The proposed research has a potential benefit for society because it is aimed at developing a fundamental understanding of how to decrease power dissipation for bit of information, a trend as important as miniaturization of devices. The impact for education will include curriculum development in a nanoscience course for graduate students and advanced undergraduates, which aims at training of future quantum engineers, fulfilling an important societal need. Both the PI and a postdoctoral researcher funded via the proposed program will actively engage in discussions of the program projects with the diverse group of graduate students of the PI research group. A topical website on dissipation and decoherence linked to the Purdue Department of Physics and the Birck Nanotechnology Center websites will be focused on broad dissemination of the expected research results in order to enhance scientific and technological understanding.