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Control of Inhomogeneous Spin Ensembles
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Robust Control of Inhomogeneous Spin Ensembles M x y M
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Compensation and Composite Pulses z x y
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Robust Control of Inhomogeneous Spin Ensembles M x y M
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The problem of manipulating quantum systems with uncertainities or inhomogeneities in parameters govering the system dynamics is ubiquitous in spectroscopy and information processing. a) Understanding what aspect of system dynamics makes compensation possible. b) What kind of inhomogeneities or errors can or cannot be corrected. Typical settings include a) Resonance offsets b) Inhomogeneities in the strength of excitation field (systematic errors) c) Time dependent noise (nonsystematic errors) d) Addressing errors or cross talk Widespread use of composite pulse sequences and pulse shaping first to correct for errors or compensate for inhomogeneties
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Broadband Control
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Lie Algebras and Polynomial Approximations
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Choosesuch that it is approx. constant for Using as generators
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Lie Algebras and Polynomial Approximations and Ensemble Controllability Create Unitary Evolution as a function of inhomogeneity to desired level of accuracy
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Basic Mathematical Structure: Non commutativity of generators and an underlying semi-simple Lie-algebra Repeated Lie brackets (commutators) will raise the dispersion parameter to higher powers. The various powers of can be combined to form polynomials that approximate any desired evolution with continuous dependency on
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Ensemble Controllability of Bloch Equations
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Larmor Dispersion and Strong Fields
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Larmor Dispersion and Bounded Controls Adiabatic Passage Adiabatic Passage is Robust to rf-inhomogeneity
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Ensemble Controllability of Bloch Equations
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Some Negative Results Nil-Potent Systems Cannot be Compensated x y
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Some Negative Results Linear systems cannot be compensated for field inhomogeneities
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Some Negative Results Phase Dispersions Cannot be Compensated
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Ensemble Controllability of Coupled Spins with Inhomogeneous Couplings
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I S NOE M x y M H
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One dimensional spectrum
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Relaxation Optimized Coherent Spectroscopy Singular Optimal Control Problems Anisotropy Compensated Experiments in Solid state NMR Theory of Broadband Control
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Inhomogeneous Broadening due to Dipolar Coupling Dispersion B0B0 S
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Broadband control in biological solid- state NMR DCP OC DCP OC HORROR HORROR J. Am. Chem. Soc., 126 (2005) Chem. Phys. Letter (2005)
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Time Optimal control of inhomogeneous quantum ensembles Find the shortest pulse sequence (shape) that produces a coherent excitation over
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Optimal control of inhomogeneous quantum ensembles Create desired excitation profile as a function of
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Minimum energy pulses for desired excitations (SLR algorithm)
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Constructive Controllability
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Applications in NMR and MRI Time optimal selective excitation, inversion and saturation pulses. Imaging and Spectroscopy in inhomogeneous fields.
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Phase correcting pulses for NMR in Inhomogeneous Static Fields X Y
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NMR in Inhomogeneous Static Fields
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Relaxation Specific Excitation
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Collaborators Steffen Glaser Burkhard Luy Frank Kramer Timo Reiss Kyryl Kobzar Andreas Spoerl Bjoern Heitmann Gerhard Wagner Dominique Frueh Takuhiro Ito Niels Nielsen Astrid Sivertsen Cindie Kehlet Morten Bjerring Technische Universitaet Muenchen Harvard Medical School University of Aarhus
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NSF Career, NSF Qubic, Sloan, DARPA, AFRL, ONR, AFOSR, Humboldt Haidong Yuan Dionisis Stefanatos Brent Pryor Dan Iancu Andrew Johnson Navin Khaneja Jr-Shin Li
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