Garett Leskowitz | California Institute of Technology (original) (raw)
Papers by Garett Leskowitz
Solid State Nuclear Magnetic Resonance, Mar 1, 1998
Ž. A novel method of nuclear magnetic resonance NMR is described which promises to be preferable ... more Ž. A novel method of nuclear magnetic resonance NMR is described which promises to be preferable to known general methods at sample length scales below ; 100 mm. Its advantages stem from the seemingly paradoxical combination of a homogeneous static magnetic field and detection of a mechanical force between a spin-bearing sample and a magnet Ž. assembly. In contrast to other methods of force-detected nuclear magnetic resonance FDNMR , the method is characterized Ž. by better observation of magnetization, enhanced resolution, and no g radient BOOMERANG , and it is generally applicable with respect to sample composition, pulse sequence, and magnetic field strength. Further advantages of portability and low cost stem from the small instrument volume and mass and promise to extend the use of NMR to new applications and environments. A sensitivity analysis, relevant to spectroscopy or imaging, quantifies the advantage of BOOMERANG relative to magnetic induction using microcoils and to FDNMR methods that rely on large gradients of the magnetic field at the sample. q 1998 Elsevier Science B.V.
Journal of Magnetic Resonance, Jun 1, 2004
We detail the uniform-sign cross-peak double-quantum-filtered correlation spectroscopy (UC2QF COS... more We detail the uniform-sign cross-peak double-quantum-filtered correlation spectroscopy (UC2QF COSY) experiment, a new through-bond correlation method for disordered solids. This experiment is a refocused version of the popular double-quantumfiltered correlation spectroscopy experiment in liquids. Its key feature is that it provides in-phase and doubly absorptive line shapes, which renders it robust for chemical shift correlation in solids. Both theory and experiment point to distinct advantages of this protocol, which are illustrated by several experiments under challenging conditions, including fast magic-angle spinning (30 kHz), anisotropic molecular motion, and 13 C correlation spectroscopy at the natural abundance isotope level.
LPI, Mar 1, 1999
Nuclear magnetic resonance (NMR) is the premier spectroscopic method for studying molecular struc... more Nuclear magnetic resonance (NMR) is the premier spectroscopic method for studying molecular structure and dynamics in condensed phases. Mineralogical1 and astrobiological applications of NMR are of interest to NASA, especially for in-situ planetary exploration. Detection and ...
Proceedings of SPIE, Feb 5, 1990
Real-time in situ monitoring of the chemical states of epoxy resins was investigated during cure ... more Real-time in situ monitoring of the chemical states of epoxy resins was investigated during cure in an autoclave using infrared evanescent spectroscopy. Fiber evanescent sensors were developed which may be sandwiched between the plies of the prepreg sample. A short length of sapphire fiber was used as the sensor cell portion of the fiber probe. Heavy metal fluoride glass optical
Journal of Chemical Physics, Jul 15, 2003
We report the first implementation of NMR quantum information processing in a static single-cryst... more We report the first implementation of NMR quantum information processing in a static single-crystal solid, illustrating pseudopure state preparation and gate manipulations on a three-qubit system, U–13C2, N15-glycine (H215N13CH213COOH). We consider issues important to single-crystal NMR implementations of quantum information processing and introduce several innovations specific to such implementations. In particular, concurrent cross-polarization of both the C13 and N15 spins from proton magnetization enhances and equalizes populations on these nuclei in a single step. This multiple cross-polarization step simplifies preparation of pseudopure spin states relative to previously described multiple-pulse sequences. Also, proton decoupling, which prolongs coherence during spin-evolution and detection periods, is switched off to dephase unwanted coherences during preparation of pseudopure spin states. Such “relaxation averaging” (or T2 averaging) is an alternative to spatial averaging, which requires special hardware and large gradient strengths for small crystals.
MRS Proceedings, 1989
The authors will review the methods used to characterize infrared transmitting optical fibers. Th... more The authors will review the methods used to characterize infrared transmitting optical fibers. The use of FTIR spectroscopic techniques for the measurement of fiber loss will be discussed. Fiber end preparation and fiber cleaving techniques will be reviewed. Data will be presented on silica fiber in the extended IR region, heavy metal fluoride, chalcogenide, silver halide fibers and sapphire crystalline fiber.
Trends in Analytical Chemistry, Oct 1, 2016
Cost and workflow considerations can render high-field NMR spectrometers a poor match for hands-o... more Cost and workflow considerations can render high-field NMR spectrometers a poor match for hands-on learning in an undergraduate teaching laboratory curriculum. Recent developments in permanent magnet technology have enabled a new class of NMR instrumentation: the benchtop spectrometer. These small, affordable, low-field NMR spectrometers (40-80 MHz) can easily be incorporated into undergraduate teaching laboratory courses. This review details the current state of benchtop NMR spectrometer use in academia, highlighting both existing benchtop and selected low-field NMR undergraduate laboratory exercises. This suite of experiments is supplemented with some high-field NMR experiments that are conducive to translation to the benchtop.
Physical Review A, May 6, 2004
Reconstruction of a reduced density operator for weakly coupled systems of spins 1 2 from fits to... more Reconstruction of a reduced density operator for weakly coupled systems of spins 1 2 from fits to nuclear magnetic resonance spectra is described in detail. Particular emphasis is placed on data treatment procedures that specify fewer than the 3 n complete spectra that are implicitly prescribed in published references to state tomography on n-spin systems. It is shown that if the density operator is expanded in the so-called productoperator basis, it is always possible to estimate a desired coefficient in the expansion by measuring a single spectral multiplet. This simple observation can substantially reduce the experimental effort required for either complete density-matrix reconstruction or estimation of subsets of the coefficients in the product-operator expansion. A simple iterative algorithm can be used to produce reduced measurement procedures for experiments involving small numbers of qubits.
APS March Meeting Abstracts, Mar 1, 1998
We present the magnetic and mechanical principles underlying a novel device for measuring low-fre... more We present the magnetic and mechanical principles underlying a novel device for measuring low-frequency changes in the magnetization of a sample. Developed primarily as a high-sensitivity method for force-detected magnetic resonance (FDMR) in homogeneous fields, it also appears that it will be competitive in other situations where the alternating coupling to the instrument is provided by nonresonant methods, such as
APS, Mar 1, 1998
The BOOMERANG (better observation of magnetization, enhanced resolution, and no gradient) approac... more The BOOMERANG (better observation of magnetization, enhanced resolution, and no gradient) approach to force-detected nuclear magnetic resonance (FDNMR) shares, with inductive detection, generality with respect to the field gradient (if any) across the sample, the usable pulse sequences, and the sample composition. We review the scaling relationships which determine which of these methods has better sensitivity in various situations and
APS, Mar 1, 1998
Spin noise is the intrinsic quantum-statistical uncertainty in a measurement of spin angular mome... more Spin noise is the intrinsic quantum-statistical uncertainty in a measurement of spin angular momentum. It poses a long-standing bound on the sensitivity of nuclear magnetic resonance (NMR). This problem is brought to the forefront by proposed force-detected NMR spectroscopy experiments, for which spin noise is anticipated to be the dominant source of noise. For N spins 1/2 with ensemble polarization
Smart Sensors, Actuators, and MEMS II, 2005
NASA's planetary exploration strategy is primarily targeted to the detection of extant or extinct... more NASA's planetary exploration strategy is primarily targeted to the detection of extant or extinct signs of life. Thus, the agency is moving towards more in-situ landed missions as evidenced by the recent, successful demonstration of twin Mars Exploration Rovers. Also, future robotic exploration platforms are expected to evolve towards sophisticated analytical laboratories composed of multi-instrument suites. MEMS technology is very attractive for in-situ planetary exploration because of the promise of a diverse and capable set of advanced, low mass and low-power devices and instruments. At JPL, we are exploiting this diversity of MEMS for the development of a new class of miniaturized instruments for planetary exploration. In particular, two examples of this approach are the development of an Electron Luminescence X-ray Spectrometer (ELXS), and a Force-Detected Nuclear Magnetic Resonance (FDNMR)-Spectrometer. The ELXS is a compact (< 1 kg) electron-beam based microinstrument that can determine the chemical composition of samples in air via electron-excited x-ray fluorescence and cathodoluminescence. The enabling technology is a 200-nm-thick, MEMS-fabricated silicon nitride membrane that encapsulates the evacuated electron column while yet being thin enough to allow electron transmission into the ambient atmosphere. At a 2-mm diameter, the MEMS FDNMR spectrometer will be the smallest NMR spectrometer in the world. The significant innovation in this technology is the ability to immerse the sample in a homogenous, uniform magnetic field required for high-resolution NMR spectroscopy. The NMR signal is detected using the principle of modulated dipole-dipole interaction between the sample's nuclear magnetic moment and a 60-micron-diameter detector magnet. Finally, the future development path for both of these technologies, culminating ultimately in infusion into space missions, is discussed.
APS March Meeting Abstracts, Mar 1, 2000
The BOOMERANG (better observation of magnetization, enhanced resolution, and no gradient) method ... more The BOOMERANG (better observation of magnetization, enhanced resolution, and no gradient) method [1] provides force detection of NMR independent of the magnetic field gradient at the sample, enabling the many spectroscopic and high-throughput imaging methods developed with inductive NMR to scale favorably to small sample size. Experiments at millimeter scale on both solids and liquids quantitatively confirm the predictions for spin-dependent force amplitude, Brownian motion noise, and oscillator softening by negative magnetic spring constant that motivate scaling to smaller size. A novel phase-cycling scheme improves the adiabaticity of cyclic spin inversion. Simulations of signal and instrument noise quantify prospects for sub-monolayer sensitivity at the scale of tens of microns with known methods for surface polarization enhancement. For nanoscale and single-molecule studies, an essential additional ingredient is the CONQUEST measurement paradigm [2] for mitigating spin noise. With unpolarized spins, this enables coherent time-domain spectroscopy, as well as imaging with arbitrary numbers of spins in each pixel. 1. Leskowitz, Madsen, and Weitekamp, Sol. St. NMR 11, 73 (1998). 2. Carson, Madsen, Leskowitz, and Weitekamp, BAPS 44(1), Part 1, 541 (1999).
Journal of Magnetic Resonance, 2004
We detail the uniform-sign cross-peak double-quantum-filtered correlation spectroscopy (UC2QF COS... more We detail the uniform-sign cross-peak double-quantum-filtered correlation spectroscopy (UC2QF COSY) experiment, a new through-bond correlation method for disordered solids. This experiment is a refocused version of the popular double-quantumfiltered correlation spectroscopy experiment in liquids. Its key feature is that it provides in-phase and doubly absorptive line shapes, which renders it robust for chemical shift correlation in solids. Both theory and experiment point to distinct advantages of this protocol, which are illustrated by several experiments under challenging conditions, including fast magic-angle spinning (30 kHz), anisotropic molecular motion, and 13 C correlation spectroscopy at the natural abundance isotope level.
Research in liquid- and solid-state nuclear magnetic resonance. Electric field effects, pulse mod... more Research in liquid- and solid-state nuclear magnetic resonance. Electric field effects, pulse modeling and design. Demonstrated first implementation of quantum information processing in a single crystal. • Graduate Research California Institute of Technology Invented a new force-detection method and apparatus for observing nuclear magnetic resonance with increased sensitivity and resolution relative to prior-art methods for microscopic samples. Analyzed method of suppressing quantumstatistical noise in measurements using time-correlated observables.
The BOOMERANG (better observation of magnetization, enhanced resolution, and no gradient) approac... more The BOOMERANG (better observation of magnetization, enhanced resolution, and no gradient) approach to force-detected nuclear magnetic resonance (FDNMR) shares, with inductive detection, generality with respect to the field gradient (if any) across the sample, the usable pulse sequences, and the sample composition. We review the scaling relationships which determine which of these methods has better sensitivity in various situations and
Solid State Nuclear Magnetic Resonance, Mar 1, 1998
Ž. A novel method of nuclear magnetic resonance NMR is described which promises to be preferable ... more Ž. A novel method of nuclear magnetic resonance NMR is described which promises to be preferable to known general methods at sample length scales below ; 100 mm. Its advantages stem from the seemingly paradoxical combination of a homogeneous static magnetic field and detection of a mechanical force between a spin-bearing sample and a magnet Ž. assembly. In contrast to other methods of force-detected nuclear magnetic resonance FDNMR , the method is characterized Ž. by better observation of magnetization, enhanced resolution, and no g radient BOOMERANG , and it is generally applicable with respect to sample composition, pulse sequence, and magnetic field strength. Further advantages of portability and low cost stem from the small instrument volume and mass and promise to extend the use of NMR to new applications and environments. A sensitivity analysis, relevant to spectroscopy or imaging, quantifies the advantage of BOOMERANG relative to magnetic induction using microcoils and to FDNMR methods that rely on large gradients of the magnetic field at the sample. q 1998 Elsevier Science B.V.
Journal of Magnetic Resonance, Jun 1, 2004
We detail the uniform-sign cross-peak double-quantum-filtered correlation spectroscopy (UC2QF COS... more We detail the uniform-sign cross-peak double-quantum-filtered correlation spectroscopy (UC2QF COSY) experiment, a new through-bond correlation method for disordered solids. This experiment is a refocused version of the popular double-quantumfiltered correlation spectroscopy experiment in liquids. Its key feature is that it provides in-phase and doubly absorptive line shapes, which renders it robust for chemical shift correlation in solids. Both theory and experiment point to distinct advantages of this protocol, which are illustrated by several experiments under challenging conditions, including fast magic-angle spinning (30 kHz), anisotropic molecular motion, and 13 C correlation spectroscopy at the natural abundance isotope level.
LPI, Mar 1, 1999
Nuclear magnetic resonance (NMR) is the premier spectroscopic method for studying molecular struc... more Nuclear magnetic resonance (NMR) is the premier spectroscopic method for studying molecular structure and dynamics in condensed phases. Mineralogical1 and astrobiological applications of NMR are of interest to NASA, especially for in-situ planetary exploration. Detection and ...
Proceedings of SPIE, Feb 5, 1990
Real-time in situ monitoring of the chemical states of epoxy resins was investigated during cure ... more Real-time in situ monitoring of the chemical states of epoxy resins was investigated during cure in an autoclave using infrared evanescent spectroscopy. Fiber evanescent sensors were developed which may be sandwiched between the plies of the prepreg sample. A short length of sapphire fiber was used as the sensor cell portion of the fiber probe. Heavy metal fluoride glass optical
Journal of Chemical Physics, Jul 15, 2003
We report the first implementation of NMR quantum information processing in a static single-cryst... more We report the first implementation of NMR quantum information processing in a static single-crystal solid, illustrating pseudopure state preparation and gate manipulations on a three-qubit system, U–13C2, N15-glycine (H215N13CH213COOH). We consider issues important to single-crystal NMR implementations of quantum information processing and introduce several innovations specific to such implementations. In particular, concurrent cross-polarization of both the C13 and N15 spins from proton magnetization enhances and equalizes populations on these nuclei in a single step. This multiple cross-polarization step simplifies preparation of pseudopure spin states relative to previously described multiple-pulse sequences. Also, proton decoupling, which prolongs coherence during spin-evolution and detection periods, is switched off to dephase unwanted coherences during preparation of pseudopure spin states. Such “relaxation averaging” (or T2 averaging) is an alternative to spatial averaging, which requires special hardware and large gradient strengths for small crystals.
MRS Proceedings, 1989
The authors will review the methods used to characterize infrared transmitting optical fibers. Th... more The authors will review the methods used to characterize infrared transmitting optical fibers. The use of FTIR spectroscopic techniques for the measurement of fiber loss will be discussed. Fiber end preparation and fiber cleaving techniques will be reviewed. Data will be presented on silica fiber in the extended IR region, heavy metal fluoride, chalcogenide, silver halide fibers and sapphire crystalline fiber.
Trends in Analytical Chemistry, Oct 1, 2016
Cost and workflow considerations can render high-field NMR spectrometers a poor match for hands-o... more Cost and workflow considerations can render high-field NMR spectrometers a poor match for hands-on learning in an undergraduate teaching laboratory curriculum. Recent developments in permanent magnet technology have enabled a new class of NMR instrumentation: the benchtop spectrometer. These small, affordable, low-field NMR spectrometers (40-80 MHz) can easily be incorporated into undergraduate teaching laboratory courses. This review details the current state of benchtop NMR spectrometer use in academia, highlighting both existing benchtop and selected low-field NMR undergraduate laboratory exercises. This suite of experiments is supplemented with some high-field NMR experiments that are conducive to translation to the benchtop.
Physical Review A, May 6, 2004
Reconstruction of a reduced density operator for weakly coupled systems of spins 1 2 from fits to... more Reconstruction of a reduced density operator for weakly coupled systems of spins 1 2 from fits to nuclear magnetic resonance spectra is described in detail. Particular emphasis is placed on data treatment procedures that specify fewer than the 3 n complete spectra that are implicitly prescribed in published references to state tomography on n-spin systems. It is shown that if the density operator is expanded in the so-called productoperator basis, it is always possible to estimate a desired coefficient in the expansion by measuring a single spectral multiplet. This simple observation can substantially reduce the experimental effort required for either complete density-matrix reconstruction or estimation of subsets of the coefficients in the product-operator expansion. A simple iterative algorithm can be used to produce reduced measurement procedures for experiments involving small numbers of qubits.
APS March Meeting Abstracts, Mar 1, 1998
We present the magnetic and mechanical principles underlying a novel device for measuring low-fre... more We present the magnetic and mechanical principles underlying a novel device for measuring low-frequency changes in the magnetization of a sample. Developed primarily as a high-sensitivity method for force-detected magnetic resonance (FDMR) in homogeneous fields, it also appears that it will be competitive in other situations where the alternating coupling to the instrument is provided by nonresonant methods, such as
APS, Mar 1, 1998
The BOOMERANG (better observation of magnetization, enhanced resolution, and no gradient) approac... more The BOOMERANG (better observation of magnetization, enhanced resolution, and no gradient) approach to force-detected nuclear magnetic resonance (FDNMR) shares, with inductive detection, generality with respect to the field gradient (if any) across the sample, the usable pulse sequences, and the sample composition. We review the scaling relationships which determine which of these methods has better sensitivity in various situations and
APS, Mar 1, 1998
Spin noise is the intrinsic quantum-statistical uncertainty in a measurement of spin angular mome... more Spin noise is the intrinsic quantum-statistical uncertainty in a measurement of spin angular momentum. It poses a long-standing bound on the sensitivity of nuclear magnetic resonance (NMR). This problem is brought to the forefront by proposed force-detected NMR spectroscopy experiments, for which spin noise is anticipated to be the dominant source of noise. For N spins 1/2 with ensemble polarization
Smart Sensors, Actuators, and MEMS II, 2005
NASA's planetary exploration strategy is primarily targeted to the detection of extant or extinct... more NASA's planetary exploration strategy is primarily targeted to the detection of extant or extinct signs of life. Thus, the agency is moving towards more in-situ landed missions as evidenced by the recent, successful demonstration of twin Mars Exploration Rovers. Also, future robotic exploration platforms are expected to evolve towards sophisticated analytical laboratories composed of multi-instrument suites. MEMS technology is very attractive for in-situ planetary exploration because of the promise of a diverse and capable set of advanced, low mass and low-power devices and instruments. At JPL, we are exploiting this diversity of MEMS for the development of a new class of miniaturized instruments for planetary exploration. In particular, two examples of this approach are the development of an Electron Luminescence X-ray Spectrometer (ELXS), and a Force-Detected Nuclear Magnetic Resonance (FDNMR)-Spectrometer. The ELXS is a compact (< 1 kg) electron-beam based microinstrument that can determine the chemical composition of samples in air via electron-excited x-ray fluorescence and cathodoluminescence. The enabling technology is a 200-nm-thick, MEMS-fabricated silicon nitride membrane that encapsulates the evacuated electron column while yet being thin enough to allow electron transmission into the ambient atmosphere. At a 2-mm diameter, the MEMS FDNMR spectrometer will be the smallest NMR spectrometer in the world. The significant innovation in this technology is the ability to immerse the sample in a homogenous, uniform magnetic field required for high-resolution NMR spectroscopy. The NMR signal is detected using the principle of modulated dipole-dipole interaction between the sample's nuclear magnetic moment and a 60-micron-diameter detector magnet. Finally, the future development path for both of these technologies, culminating ultimately in infusion into space missions, is discussed.
APS March Meeting Abstracts, Mar 1, 2000
The BOOMERANG (better observation of magnetization, enhanced resolution, and no gradient) method ... more The BOOMERANG (better observation of magnetization, enhanced resolution, and no gradient) method [1] provides force detection of NMR independent of the magnetic field gradient at the sample, enabling the many spectroscopic and high-throughput imaging methods developed with inductive NMR to scale favorably to small sample size. Experiments at millimeter scale on both solids and liquids quantitatively confirm the predictions for spin-dependent force amplitude, Brownian motion noise, and oscillator softening by negative magnetic spring constant that motivate scaling to smaller size. A novel phase-cycling scheme improves the adiabaticity of cyclic spin inversion. Simulations of signal and instrument noise quantify prospects for sub-monolayer sensitivity at the scale of tens of microns with known methods for surface polarization enhancement. For nanoscale and single-molecule studies, an essential additional ingredient is the CONQUEST measurement paradigm [2] for mitigating spin noise. With unpolarized spins, this enables coherent time-domain spectroscopy, as well as imaging with arbitrary numbers of spins in each pixel. 1. Leskowitz, Madsen, and Weitekamp, Sol. St. NMR 11, 73 (1998). 2. Carson, Madsen, Leskowitz, and Weitekamp, BAPS 44(1), Part 1, 541 (1999).
Journal of Magnetic Resonance, 2004
We detail the uniform-sign cross-peak double-quantum-filtered correlation spectroscopy (UC2QF COS... more We detail the uniform-sign cross-peak double-quantum-filtered correlation spectroscopy (UC2QF COSY) experiment, a new through-bond correlation method for disordered solids. This experiment is a refocused version of the popular double-quantumfiltered correlation spectroscopy experiment in liquids. Its key feature is that it provides in-phase and doubly absorptive line shapes, which renders it robust for chemical shift correlation in solids. Both theory and experiment point to distinct advantages of this protocol, which are illustrated by several experiments under challenging conditions, including fast magic-angle spinning (30 kHz), anisotropic molecular motion, and 13 C correlation spectroscopy at the natural abundance isotope level.
Research in liquid- and solid-state nuclear magnetic resonance. Electric field effects, pulse mod... more Research in liquid- and solid-state nuclear magnetic resonance. Electric field effects, pulse modeling and design. Demonstrated first implementation of quantum information processing in a single crystal. • Graduate Research California Institute of Technology Invented a new force-detection method and apparatus for observing nuclear magnetic resonance with increased sensitivity and resolution relative to prior-art methods for microscopic samples. Analyzed method of suppressing quantumstatistical noise in measurements using time-correlated observables.
The BOOMERANG (better observation of magnetization, enhanced resolution, and no gradient) approac... more The BOOMERANG (better observation of magnetization, enhanced resolution, and no gradient) approach to force-detected nuclear magnetic resonance (FDNMR) shares, with inductive detection, generality with respect to the field gradient (if any) across the sample, the usable pulse sequences, and the sample composition. We review the scaling relationships which determine which of these methods has better sensitivity in various situations and