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Coherent Control of Electron Spins in Diamond for Quantum Information

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Coherent Control of Electron Spins in Diamond for Quantum Information Coherent control of electron spins in diamond for quantum information science and quantum sensing by Alexandre Cooper-Roy B.Eng., École Polytechnique de Montréal (2008) Ingénieur Polytechnicien, École Polytechnique (2009) M.Eng., The University of Tokyo (2010) Submitted to the Department of Nuclear Science and Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY September 2016 c Massachusetts Institute of Technology 2016. All rights reserved. ○ Author................................................................ Department of Nuclear Science and Engineering July 22nd, 2016 Certified by. Paola Cappellaro Associate Professor Thesis Supervisor Accepted by........................................................... Ju Li Chairman, Department Committee on Graduate Theses 2 Coherent control of electron spins in diamond for quantum information science and quantum sensing by Alexandre Cooper-Roy Submitted to the Department of Nuclear Science and Engineering on July 22nd, 2016, in partial fulfillment of the requirements for the degree of Doctor of Philosophy Abstract This thesis introduces and experimentally demonstrates coherent control techniques to exploit electron spins in diamond for applications in quantum information process- ing and quantum sensing. Specifically, optically-detected magnetic resonance mea- surements are performed on quantum states of single and multiple electronic spins associated with nitrogen-vacancy centers and other paramagnetic centers in synthetic diamond crystals. We first introduce and experimentally demonstrate the Walsh reconstruction method as a general framework to estimate the parameters of deterministic and stochastic fields with a quantum probe. Our method generalizes sampling techniques basedon dynamical decoupling sequences and enables measuring the temporal profile of time- varying magnetic fields in the presence of dephasing noise. We then introduce and experimentally demonstrate coherent control techniques to identify, integrate, and exploit unknown quantum systems located in the environment of a quantum probe. We first locate and identify two hybrid electron-nuclear spins systems associated with unknown paramagnetic centers in the environment of a single nitrogen-vacancy center in diamond. We then prepare, manipulate, and measure their quantum states using cross-polarization sequences, coherent feedback techniques, and quantum measurements. We finally create and detect entangled states of up tothree electron spins to perform environment-assisted quantum metrology of time-varying magnetic fields. These results demonstrate a scalable approach to create entangled states of many particles with quantum resources extracted from the environment of a quantum probe. Applications of these techniques range from real-time functional imaging of neural activity at the level of single neurons to magnetic resonance spec- troscopy and imaging of biological complexes in living cells and characterization of the structure and dynamics of magnetic materials. Thesis Supervisor: Paola Cappellaro Title: Associate Professor 3 4 Acknowledgments This thesis has been made possible by the financial support from the Fulbright Scholar Program and the Natural Sciences and Engineering Research Council of Canada. A very special thank you goes to all of my mentors, colleagues, and friends at MIT, Harvard, and elsewhere in the world who have helped me become the person I am today. First and foremost, Professor Paola Cappellaro has been very keen on supervising my research activities and guiding my scientific growth during my tenure within her group. Paola has provided me with a tremendous amount of freedom to explore cre- ative approaches to identifying and solving problems in science and engineering. She has always been very open to discuss new ideas and provide feedback on my progress towards reaching my goals. Paola is a very dedicated and thoughtful mentor with an inspiring motivation to better understand the quantum world and a great ability to combine a deep understanding of theoretical concepts with insightful experimental evidences. Professor Ju Li has provided me with many valuable advice as the chairman of the committees of both my qualifying exam and my thesis defense, including the importance of making connections with the work of others and focusing on solutions that enable discoveries and new technologies. Professor Dirk Englund has provided me with many valuable advice about my scientific research and career goals as an academic advisor and member of mythesis committee. I very much admire the ability of Dirk to carry out collaborative re- search projects on multidisciplinary fronts at the confluence of scientific disciplines and thank him for providing me with such great opportunities to learn from the numerous members of his group. Professor Ronald Walsworth from the Center for Astrophysics (CFA) at Har- vard University has been an inspiring role model who taught me by example about the importance and excitement of building strong collaborative teams and tackling challenging problems at the intersection of multiple fields of research. Ron has sig- 5 nificantly contributed to the success of my research by encouraging me to attendhis group meetings and exchange (classical) information and matter with his postdocs and students. Professor Ed Boyden from the Media Lab at MIT has taught me through many intense discussions about the importance of maximizing impact by solving the most important problems facing humanity, identifying valuable opportunities by using a wide variety of cognitive tools, and maintaing strong collaborative ties with experts across disciplines. Many other professors have also helped shaping my scientific growth, including Professors Lorenza Viola from Dartmouth University, Dmitry Pushin from University of Waterloo, Nir Bar-Gill from the Hebrew University of Jerusalem, and Michael Biercuk from the University of Sydney. Second, I would like to acknowledge the help and friendship of all of the postdocs that have spent time with me discussing about Science, have taught me experimental skills and theoretical concepts, and have encouraged my quest for knowledge with key insights and pieces of equipment. HoNam Yum has taught me valuable experimental skills in optics and electronics as we worked together on designing and building our first confocal microscope. Easwar Magesan has cheerfully joined my efforts to work out the theory of the Walsh reconstruction method and compressed sensing approach to quantum param- eter estimation. Easwar’s enthusiasm for solving tough mathematical problems has positively influenced my approach to research. Gerardo Paz-Silva from Dartmouth University has taught me a lot about noise spectroscopy and the Magnus expansion during many of our visits and video calls. Chinmay Belthangady from Walsworth group at Harvard has spent a great deal of his time at MIT to help me set up the electronics for driving electron spins in diamond as we launched our new project on environment-assisted quantum metrology. Chinmay’s positive and generous attitude has inspired me to become a better person. Huiliang Zhang from Walsworth group at Harvard has answered many of my questions about diamond fabrication and has patterned and implanted the diamond 6 sample in which we ended up identifying two unknown paramagnetic centers. Many other postdocs have contributed to my theoretical and experimental research work. David Gelbwaser from Aspuru-Guzik group at Harvard has spent many hours with me discussing about quantum thermodynamics and the efficiency of quantum engines. Jean-Christophe Jaskula has taught me about super-resolution microscopy and has helped me resolving technical issues with our confocal microscope. Luca Marseglia has helped out fabricating new coplanar waveguides and acid cleaning our diamond samples. David Le Sage taught me about aligning an acousto-optic mod- ulator in the bow-tie configuration. David Glenn has provided me with technical guidance in building our first confocal microscope and has fueled my interest in bio- physics. Alexei Trifonov has helped diagnosing issues in our optical setup. Linh Pham has answered many of my questions about handling diamond samples and perform- ing magnetometry experiments; her lablog posts have always been a great source of inspiration. Ulf Bissbort has taught me about solving algebraic expressions in spin physics using the C programming language. Kasturi Saha has helped fixing issues in our optical setup. Gurneet Kaur has provided me with great advice about recording scientific information and experimental measurements. Third, I would like to acknowledge the friendship of my student colleagues from the Quantum Engineering Group, which have played an important role in shaping my experience at MIT. Clarice Aiello wrote the first version of our control software and provided valuable support in designing and building our control electronics to manipulate the quantum state of single nitrogen-vacancy centers in diamond. Masashi Hirose provided me with the source code to simulate the dynamics of confined ensembles of interacting electron spins and engaged me in many discussions about understanding new sets of experimental data. Ashok Ajoy provided support on automating the alignment of the static magnetic field and contributed to many discussions on performing spectral measurements on ensembles of electron spins. Ken Xuan Wei provided me with the source
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