NER: Single Molecule Magnets for Quantum Computing

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AbstractProposal No: 304665Title: NER: Single Molecule Magnets for Quantum ComputingWe are proposing a 1-year nanoscale exploratory research (NER) in the technologically and fundamentally important area of single molecule magnets (SMM) whose application in quantum computing has been the subject of intense speculation. The SMM's typically consist of 2 to 15 magnetic ions embedded in non-magnetic ligand groups. The magnetic interaction strengths within each SMM are in the range 1-100K, while that between SMM's is about 10 mK. These exchange interactions maybe ferromagnetic (FM) or antiferromagnetic (AFM). Although the AFM SMM's appear to exhibit more interesting low temperature quantum effects than do the FM SMM's, the latter have attracted a considerable interest, due to the suggestion that their properties might be exploited to construct useful magnetic storage devices and quantum computers. The two SMM's studied most extensively experimentally, Fe8 and Mn12, have multiple spin-spin interactions within a SMM unit, consisting of both FM and AFM signs, and are difficult to model theoretically. However, since a number of smaller SMM's can be made with magnetic cores that consist of as few as 2-4 magnetic ions, we propose to study initially the effects of the magnetic interactions within SMM's consisting of 3-4 magnetis ions in the electron paramagnetic resonance (EPR) configuration. This environment consists of a constant magnetic induction of strength B0 and a transverse oscillatory magnetic induction with frequency ?0 and strength B1, and can be used to investigate if the SMM's have special features that might allow one to read and write information on the scale of 1-2 nm using a static field that contains a large spatial gradient. By comparing these quantum results with the classical results for the dynamics of these systems, as measured by the various time correlation functions, better understanding would be possible for the larger systems. Such exactly solvable systems will also be studied to investigate the severity of the decoherence that can arise after a SMM has been excited by the oscillatory magnetic induction. This can be investigated by analyzing the EPR linewidths. The information obtained in this exploratory research is expected to provide the knowledge base necessary for developing reliable numerical methods to simulate the behavior of larger systems like Fe8 and Mn12 of more practical interest. A significant outcome of the proposed research will be the education and training of junior members of the PI's group in a subject at the forefront of exploratory research for future applications. Because of the simplicity of the systems, results of the research will be used by the PI for general educational purposes and broader dissemination to the educational community.