Insider Brief<\/p>\n
SLAC National Accelerator Laboratory<\/a> scientist Shannon Harvey is developing scalable quantum dot qubits as part of the Q-NEXT quantum research center.<\/p>\n Harvey\u2019s research focuses on designing silicon-based quantum dots that can be manufactured at scale while addressing challenges such as noise and qubit control.<\/p>\n The work explores quantum dot technologies as a potential pathway toward building larger quantum processors using semiconductor-compatible approaches.<\/p>\n Press release \u2013 Studying an object with zero dimensions takes serious creativity. Consider the singularity \u2014 a point packed with infinite energy that sparked the Big Bang. Or the humble mathematical point, an abstract but indispensable fixture in space-time. Grasping a thing that has no size or shape demands imagination and rigor.<\/p>\n Or take qubits. Manipulating these zero-dimensional, information-carrying ripples in quantum space requires mental and manual dexterity. Yet those who work on qubits seldom tout the rich set of skills they bring to bear on their research.<\/p>\n The scientific endeavor\u2019s many creative dimensions are what drew Shannon Harvey to the work of finessing these dimensionless bits of information.<\/p>\n \u201cWhat I love about working in quantum information is that we can use today\u2019s technologies to play with nature\u2019s quantum features, something that until recently would have seemed incredible,\u201d said Harvey, a scientist at the U.S. Department of Energy\u2019s (DOE)\u00a0SLAC<\/a>\u00a0National Accelerator Laboratory.\u00a0\u200b\u201cI really thrive on the multifaceted nature of this research, solving and coming up with problems by embedding myself in the experimental details and trying to understand how they all fit together. For me, scientific exploration involves reading and writing papers, solving math problems, even soldering and welding. Often within the same day.\u201d<\/p>\n Harvey brings her multifaceted set of skills to\u00a0Q-NEXT<\/a>, a\u00a0DOE\u00a0National Quantum Information Science Research Center led by\u00a0DOE\u2019s Argonne National Laboratory in partnership with\u00a0SLAC<\/a>. A national research hub, Q-NEXT aims to coax nature\u2019s quantum features into sharing information over distances large and small. It\u2019s a collaborative effort that\u2019s helped by a knack for futzing with particles.<\/p>\n The particle of Harvey\u2019s attention is a type of qubit called a quantum dot.<\/p>\n Picture an electron, a tiny ripple bopping around inside a tiny space. Now imagine fencing it in so tightly that it\u2019s trapped in an even smaller space, smaller than its own wavelength \u2014 like putting up walls that hug someone so closely, they have no room to lift their arms. Hemmed in, the electron is compelled by the rules of physics to take on a set of specific energy values. Its wave transforms into a set of distinct wavelengths, like a chord separating into a series of pure tones. Those discrete energies let scientists fine-tune and control how the electron stores and shares information.<\/p>\n That\u2019s a quantum dot: a particle that\u2019s confined to a space smaller than its wavelength, transformed into an object with multiple energy values. (One might say that the particle is squeezed for information.)<\/p>\n The qubit is the basis of quantum technologies, which are expected to speed up drug discovery, make financial transactions more secure, provide eavesdrop-proof telecommunication and more. As a qubit species, the quantum dot has a lot going for it. For one, it\u2019s tunable, like a radio, so it can share information over different frequencies depending on how it\u2019s used. And, most relevant for Harvey\u2019s research, quantum dots can be mass-produced.<\/p>\n \u201cThe real selling point of quantum dot qubits is that they\u2019re scalable,\u201d Harvey said.\u00a0\u200b\u201cYou can put a ton of them on a chip and then build a quantum computer on that chip.\u201d<\/p>\n That\u2019s the dream: a chip that contains multitudes. Harvey and her colleagues are designing quantum dots so they can crowd millions \u2014 or even billions \u2014 onto a something the size of a drink coaster. That scalability is both a feature and a bug, Harvey said.<\/p>\n Scalability means quantum dots can be made affordably; perform consistently and reliably; and can compatibly work with larger systems and existing technologies.<\/p>\n The challenge \u2014 the bug \u2014 is that a chip chock-a-block with dots is noisy. The noise muddles the qubit\u2019s signal.<\/p>\n \u201cYou want to be able to control the qubit\u2019s energy. If there\u2019s some noise that\u2019s causing the energy to fluctuate in time, you\u2019ll lose the knowledge of what your qubit is doing, lose control. And then the qubit stops being useful,\u201d Harvey said.<\/p>\n The lower the noise, the more reliable and pliable the qubit.<\/p>\n But taming noise is only half of it. Harvey\u2019s job is about more than shushing, like an usher at the symphony. She works to create a quiet environment in which a massive quantum dot brigade can perform harmoniously, sending and receiving data with no interference, no snags. What properties will smooth the information pathway? What\u2019s the best way to connect quantum dots to surrounding structures, which are themselves noisy? At which temperature does the quantum dot perform best? How should quantum dots be spaced to prevent interference? What software capabilities are needed to keep everything under control?<\/p>\n The work is a mix of materials science, computer science, engineering and basic physics, not to mention patience, exploration and ingenuity. Harvey reaches across the disciplinary aisle at\u00a0SLAC<\/a>\u00a0to connect with cosmologists building detectors for studying the outer universe. It\u2019s a perk of working at the\u00a0SLAC\u00a0Millikelvin Facility, where researchers explore nature at both extremes of scale.<\/p>\n \u201cIt\u2019s a really open environment. We lack walls literally. I\u2019ve learned a lot from the other people in the building who have very different expertise than I have. I never knew how similar the things I think about are to the people who are doing experiments for cosmology,\u201d she said.\u00a0\u200b\u201cIt\u2019s very different from what you see in academia. And even though it\u2019s not this huge-scale facility, it\u2019s really an example of what national labs can bring to the table. It\u2019s a special experience.\u201d<\/p>\n As a child, Harvey had\u00a0\u200b\u201czero interest in science,\u201d she said.\u00a0\u200b\u201cI just wanted to read novels all the time.\u201d She enjoyed math,\u00a0\u200b\u201cbut math was not quite enough connected to the real world. I have this wide-ranging curiosity where I want the answer to everything, and one of my main challenges is to focus down onto one thing instead of trying to work on everything.\u201d<\/p>\n As an undergraduate at Cornell University, she saw that physics gave her a way both to connect with and answer many of the questions she had about the real world.<\/p>\n \u201cI completely fell in love with experimental physics,\u201d she said.<\/p>\n