MIT Reports to the President 1998-99

FRANCIS BITTER MAGNET LABORATORY

The Francis Bitter Magnet Laboratory (FBML) has continued to make notable advances in several areas of science and engineering involving high magnetic fields. The research program in Magnetic Resonance (nuclear magnetic resonance (NMR), and electron paramagnetic resonance (EPR)) has continued to grow and remains the largest effort at the FBML. The program is funded primarily by the NIH and DOE, and involves ~20 NMR and EPR magnets and spectrometers.

Professor Robert G. Griffin, together with Professor Gerhard Wagner of Harvard University, announced The MIT/Harvard Center for Magnetic Resonance, a collaborative research effort between MIT and Harvard University. The Center is supported by a NIH Research Resource grant that was renewed for five years.

Professor Harald Schwalbe will join the Department of Chemistry in the fall of 1999. His offices and laboratories will be located at the FBML. Professor Schwalbe's area of research is solution NMR and he will fill the intellectual niche formerly occupied by Professor Jamie Williamson.

Professor Cory and his colleagues continue to make rapid advances in the theory, practice and implementation of quantum information processing. These include the first demonstrations of quantum error correction and of quantum simulation on a quantum computer.

Dr. Yukikazu Iwasa received funding from NIH to construct a very high field, wide bore 750 MHz NMR system. We expect delivery of the system late this summer or in the early fall.

Dr. Jagadeesh Moodera has continued to strengthen his research efforts in condensed matter physics through collaboration with various universities and industries, as well as the ONR and NSF. In addition, he has continued his mentoring of graduate students, undergraduate and high school students by providing research opportunities within his lab. Dr. Moodera received the 1999 TDK Research Award for his pioneering studies in spin tunneling.

Professor Cory and his students continue to explore NMR approaches to quantum information processing through a set of collaborations with Dr. T. Havel (HMS), Professor Seth Lloyd (Mechanical Engineering), Dr. Raymond Laflamme (LANL), Dr. E. Knill (LANL), Dr. J. Yepez (AFRL). Some of our recent accomplishments include:

• first demonstration of quantum error correction (an absolutely necessary component of any future quantum computer to avoid the consequences of decoherence)

• first demonstration of quantum simulation on a quantum computer (originally suggested by Feynman as a reason why a quantum computer would be useful)
• first demonstration of a coherent quantum controller (an extension of a classical controller that demonstrates the limitation QM imposes by its prescription against cloning quantum states)
• the successful implementation of all 2-qubit gates (provides a complete ‘programming language' and compiler for our quantum information processor)
• demonstrations of 4-qubit operations (the first example of fine coherent control of 4-qubit systems, which demonstrates that the scaling of gate complexity need not be exponential)
• demonstration of a 3-qubit quantum Fourier transform (the QFT is an essential component of most quantum algorithms since it sets up a state where all quantum interferences can be realized)
• demonstration of quantum stochastic resonance (a clean example of using QIP to explore the structure of decoherence)
• demonstration of the dynamics of the GHZ state (the cleanest example of a maximally entangled three quantum state)
• demonstration of the quantum eraser paradox (an NMR version of the optics experiment that has frustrated researchers for years)

We have also articulated two new schemes for extending the success of NMR approaches to QIP to larger systems and have received funding to explore a solid state device capable of coherently controlling 10—30 qubits; and a lattice gas quantum computer capable of addressing thousands of small quantum computers in parallel.

The laboratory remains at the forefront of experimental investigations of quantum information processing and is capable of exploring by far the largest Hilbert spaces of any experimental effort. We are currently working with a custom designed 6-qubit quantum processor.

We have succeeded in obtaining NMR images at 2 x 2 x 8 µm³ resolution (the highest resolution every achieved) and have applied this to the non-invasive study of anatomical changes associated with genetic mutations in fruit-flies. We are continuing to explore the biological implications of this novel technology.

We have demonstrated and published the first example of multiple scattering in NMR and shown that this can be used to characterize the local anisotropy of confined spaces. Dr. Pabitra Sen (Schlumberger-Doll Research Laboratory) will spend a year on sabbatical leave with us at MIT to extend these methods to obtain a complete characterization of local structures in complex media.

With collaborators at Bruker Instruments Inc., we have designed and built the first solid state NMR probes with a magnetic field gradient that is compatible with both high resolution spectroscopy and magic angle sample spinning. We have then demonstrated the first examples of gradient enhanced NMR of solids.

We continue studies of tissues, cultured cells, granular media and other heterogeneous materials by high resolution MAS NMR. Over the past year we have developed methods that permit the measurement of both the length scale and strength of background gradients that are introduced by spatially varying magnetic susceptibilities. We expect to characterize both the structure and dynamics of these highly complex samples by extensions of these methods. These studies are in collaboration with Dr. Samuel Singer.

We continue to develop NMR-compatible, extremely strong (100,000 G/cm) magnetic field gradients to permit structural studies of solids. Professor Cory's laboratory remains the only place in the world where such strong magnetic field gradients have been successfully used in NMR, and we continue to advance both the instrumentation and methods. We hope that eventually these methods can be applied much like neutron scattering, but at longer length scales (0.2—100 nm) and longer time scales (from ms—seconds).

In collaboration with Dr. R. Walsworth (Harvard Smithsonian), we have demonstrated that high quality NMR images can be obtained at very low fields (20 G) using optically polarized Xe as a tracer. There are a wide variety of diagnostic applications ranging from medical imaging to characterizing engineering systems and flow.

In collaborations with Professor Culligan (Civil and Environmental Engineering) and Professor Czerwinski (Nuclear Engineering), the transport of lanthanides and the displacement of contaminants in model sands, soils and resins are being studied by NMR.

Professor Robert G. Griffin's research can be found on the World Wide Web at http://web.mit.edu/fbml/cmr/griffin-group/.

The capabilities of the 140 GHz EPR spectrometer have been dramatically extended by the incorporation of a four-phase microwave pulse-forming network and amplifier with 30 mW of output power. The greater microwave power and phase switching capability now allows us to develop and perform sophisticated pulsed EPR techniques. In particular, we are working on developing new pulsed methods for spectral filtering, electron/nuclear cross polarization and multiquantum EPR experiments for measuring long-range distances (10-30 Å) in spin labeled proteins and peptides. We have also added a 140 GHz pulsed Electron-Nuclear Double Resonance (ENDOR) capability. The increased sensitivity, resolution, and orientation selection available in the ENDOR experiment at this high frequency/field has enabled us to determine in detail the electronic structure of the tyrosyl radical of ribonucleotide reductase. (RNR) ENDOR studies of the RNR inhibitor complexes and Fe-S cluster active site of the protein putidaredoxin have also been initiated. The paramagnetic Fe-S cluster precludes the characterization of the active site structure by NMR techniques due to the very large paramagnetic shifts and broadenings of the NMR resonances. High frequency ENDOR spectroscopy, however, is uniquely suited to study the active sites of such paramagnetic enzymes and proteins.

Amyloidoses are a group of peptide or protein misfolding disorders characterized by the accumulation of insoluble fibrillar protein material in extracellular spaces. Sixteen different peptides are known to form amyloid-like aggregates. The aggregation of these peptides is involved in several diseases. ß-amyloid (A) is involved in Alzheimer's disease, the conversion of the prion protein PrPc to PrPsc leads to the transmissible spongiform encephalopathie, and the synuclein protein is responsible for Parkinson's disease.

During the last year, we worked on methods to obtain large amounts of fibrillar peptide material. Fibril preparation is crucial for obtaining narrow lines, maximizing spectral resolution, and optimizing signal intensities. Fibril formation is also important for the biological relevance of the structural model. Furthermore, we have obtained ¹⁵N labeled Ab 1-40 and prepared fibrils of this material. High-resolution AFM (Atome Force Microscopy) images indicate that this fragment forms regular fibrils as well and our first ¹⁵N MAS spectra reveal resolved Arg and Lys resonances. During the coming year, we are planing serious structural studies of the Ab peptide.

During the past year we have completed the construction of a 250 GHz gyrotron for high frequency DNP experiments. The device has been operated in continuous wave mode for a few days at an output power of 25 watts. We have also installed a new 125 mm bore 375 MHz NMR magnet and a NMR spectrometer console for these experiments.

We continue to operate our 140 GHz DNP system. Notable achievements this year include the construction of a high Q resonator for DNP/ENDOR with a microwave Q ~ 2000. This permits us to perform pulsed EPR and ENDOR experiments with p /2 pulses of 70—100 ns duration corresponding to b ₁ fields of a few MHz. In addition, we have used the resonator to achieve S/N enhancements in NMR spectra of 400 ± 50.

The Center for Magnetic Resonance has completed its 23^rd year of operation as a facility open to scientists needing access to high field NMR equipment. During this year, 69 projects were worked on by 126 investigators, from departments within MIT including Chemistry, Physics and Nuclear Engineering, as well as users and collaborators from institutions outside of MIT such as Harvard University, Brandeis University and Brigham & Women's Hospital. Work resulted in 52 publications in print or in press

Highlights of work conducted at the center include advances in high frequency dynamic nuclear polarization of proteins (DNP), high precision NH Bond distance measurements in a serine protease active site and protein structure determination of Human Za.

A competing proposal was submitted to NIH for review during the summer of 1998 and is now funded for an additional five-year period.

Dr. Yukikazu Iwasa has continued research on the key operational issue of protection for high temperature superconducting (HTS) magnets operating in the temperature range 10—60 K. In addition to this basic protection study, practical aspects of cryocooler-cooled operation has been investigated. We have studied small coils wound from silver-sheathed BSCCO-2223 tapes in the temperature range 20—60 K. We have developed a numerical NZP model for a three dimensional, dry-wound, BSSCO-2223 superconducting magnet. The test magnet operates under quasi-adiabatic conditions at 20~K and above, in zero background field. The NZP model is based on the two-dimensional transient heat diffusion equation. Quenches are simulated by a numerical code using the finite-difference method. Agreement between voltage traces obtained in the test magnet during heater-induced quenching events and those computed by the numerical NZP model is reasonable. The model is also used to simulate quenching in magnets similar to the test magnet.

Our work on developing a "permanent" HTS magnet system is continuing. The system combines the simplicity and ease of operation of a ferromagnetic permanent magnet with the strength, capability and versatility in field generation of an electromagnet. Once energized and producing a desired field, the system, without being coupled to a cooling source, can maintain the field for a long period. This HTS magnet is particularly suitable for an on-board or portable unit requiring a constant field and where "permanence" means a duration of hours, days, weeks, months, or even years. The system's other features are "recooling" and "recharging" capabilities designed to have the system re-cooled while maintaining its constant field to make the field literally permanent, and recharged if its upper operating temperature is exceeded and the field decays.

An application has been filed to the U.S. Patent and Trademark Office for invention of a new high-temperature superconducting (HTS) current lead. The new HTS lead requires HTS materials that are substantially less than those required by the conventional HTS current leads that are available on the market. The core of the invention is that, in the new HTS current lead, a warm part of the HTS lead is operated in the so-called "current-sharing" (partially resistive) mode rather than completely in the superconducting state as in the conventional HTS current lead.

In condensed matter physics, in particular magnetism, Dr. Jagadeesh S. Moodera's research continues to make significant contributions to both fundamental science and industrial application. Our investigation emphasizes interfacial exchange interaction and spin transport in thin film structures. We have made further progress in unraveling the spin properties of certain exotic magnetic compounds (which are technologically important materials), using our molecular beam epitaxy (MBE) system. Our research in these materials has already shown the possibility of a four level memory/logic element - a first of such kind of thin film tunnel device. National and international collaborative research with scientists/faculty from national laboratories, US universities, the University of Paris at Orsay, the University of Eindhoven, Tohoku University and the Ukrainian Academy of Sciences are successfully continuing. Exchange of scientists and graduate students are part of this program. Several new research grants were obtained.

In the area of semiconductors, our continued research in collaboration with Hewlett-Packard Company has been valuable, in search of prospective materials for atomically resolved storage ( > Terabytes/in² ). We are exploring the materials that exhibit the right properties and giving HP the fundamental information necessary for their program. We are also establishing new collaborations with other companies such as NVE Inc., TDK (Japan) in the field of magnetism.

Three graduate students and five postdoctoral scholars have taken part in the research. Two visiting graduate students who worked under Dr. Moodera's supervision obtained their Ph.D. degrees from the University of Eindhoven and the University of Paris at Orsay. Another graduate student was awarded the "Best Student Paper" award at an international conference in 1998. The four high school students and five undergraduates who took part in the research activities won several science competitions, including a semifinalist in Westinghouse Science Competition. Another undergraduate took part in research at Los Alamos National Lab. Dr. Moodera's work resulted in twelve research publications, three invited review and over twenty invited talks at various national and international conferences, universities, labs etc. In addition, Dr. Moodera chaired many conference sessions, organized a special symposium at the Centennial American Physical Society Meeting in 1999 and received the TDK Research Award in 1999 for his research in spin tunneling.

During the past year, FBML resources were consolidated into one building. We now boast an upgraded space for 2 750 MHz NMR magnets, as well as space for the wide bore 750 MHz magnet to be built under Dr. Yukikazu Iwasa.

Newly renovated facilities have recently been provided for Professor Cory's research group, including a wet lab and a computer lab.

Professors Keith Nelson and Andrei Tokmakoff of the Department of Chemistry have moved into temporary lab space on the first floor pending the completion of their permanent laser lab facility in the Chemistry Department. Additional Chemistry faculty are also considering moving to the Magnet Lab while their spaces undergoe construction.

Extensive renovation has been complete on the second floor to provide office space for Professor Jacquelyn Yanch, Professor David Cory and their students.

The Laboratory contributes to undergraduate education by participation in the Undergraduate Research Opportunities Program (UROP) a program that encourages and supports research-based intellectual collaborations of MIT undergraduates with Institute faculty and research staff. In addition, the laboratory has 25 full-time graduate and 15 postdoctoral students performing research.

Professor Cory has explored the practicality of having students in graduate courses collectively write peer reviewed scientific papers. Two papers were written and published by students in an advanced NMR course (22.582), the first describing a novel means of analyzing multiple pulse experiments and the second describing how NMR spectroscopy can be used to demonstrate fundamental issues of quantum mechanics. The experience was quite positive and this is now an integral part of 22.582. The two papers are:

Counting Echoes: An Application of a Complete Reciprocal-Space Description of NMR Spin Dynamics, R. J. Nelson, Y. Maguire, D. Caputo, G. Leu, Y. Kang, M. Pravia, D. Tuch, Y. Weinstein, and D. G. Cory, Concepts in Magnetic Resonance, 1998, 10, 331—341.

Observing Quantum Behavior in a Spin System by NMR, M. Pravia, R. J. Nelson, Y. Weinstein, and D. G. Cory, Concepts in Magnetic Resonance, 1999, 11, 225—238.

Professor Cory and his students have started the writing of a novel textbook on quantum information processing, the "Quantum Cookbook," which shows elements of quantum mechanics and information science based on demonstrations with our NMR quantum information processor. It is expected that this book and its demonstrations will form an integral part of an introductory course on Quantum Computing and Communication.

Professor Cory has built a new teaching laboratory for exploring the physics and engineering of medical imaging. The laboratory houses demonstrations of optical, NMR, ultrasound, X-ray and PET imaging. This will be used to augment the lectures of 22.058, a new undergraduate offering by the nuclear engineering department.

The NMR implementations of quantum information processing are so well advanced now that Professor Cory's laboratory invites both undergraduates from the CMSE program and senior high school students from the RSI program to work in the laboratory over the summer on projects that demonstrate features of QIP. This last year Jeff Gore (CMSE) developed pulse sequences for both a variety of quantum gates and quantum error correction, and Chris Ackerman (RSI) helped define a NMR version of the quantum eraser paradox. This year Craig (CMSE), Swami (CMSE) and Gabriel (RSI) are working together to demonstrate the capacity of a quantum channel, the conversion of a quantum channel to a classical channel, and the role of bit commitment in quantum communication.

Professor Cory and Dr. Raymond Laflamme (LANL) organized a 4 day workshop on NMR and Quantum Information Processing that was fully funded by ARO and NSA, and held at Harvard Smithsonian Center of Atomic and Molecular Physics. The workshop was the first to bring together the NMR and QIP communities. It was very well attended and received.

Professor Cory has joined the editorial boards of the Journal of Magnetic Resonance and Concepts in Magnetic Resonance.

For several years now, we have been pursuing the development of an Imaging Center here at the Magnet Lab. These plans are being revised in conjunction with the Harvard/MIT HST program. A $20 Million gift from the Martinos family will be used to support this center.

Once construction is complete on the second floor magnet hall, instruments currently housed on the fourth and fifth floors will be relocated in order to create a comprehensive "Center for Magnetic Resonance."

A new classroom was designed to replace one lost to construction of office space on the second floor. Work on this room was completed in July, 1999.

Robert G. Griffin

MIT Reports to the President 1998-99