“It’s unusual and exciting to build bridges between physics and engineering,” says Prof. Maiken Mikkelsen, who will be doing just that in her new position as assistant professor in the departments of physics and electrical and computer engineering. “I’ll be able to supervise students from both departments and create a very interdisciplinary group. I’m excited about it,” she says. In addition to building bridges between disciplines, she’s also helping to “build” the computer of the future—a quantum computer. Quantum mechanics describes how matter and energy interact on an atomic scale, where the familiar laws of classical mechanics do not apply. “As electronics get smaller and smaller, at some point the quantum mechanics are starting to become important,” she says. “Let’s not look at quantum effects as annoyances, but build something from the ground up that is based on quantum mechanics—to use it as an advantage.”
While quantum computing is still just a gleam in physicists’ eyes, the idea is tantalizing because a quantum computer could handle much more information—and much more securely—than today’s computers. In digital computers, data is stored in switches that are either on or off—the familiar 1’s and 0’s of computer language. In a quantum computer, data is stored in quantum bits—“qubits”—that can be on, off, or essentially anywhere in between (called superposition), dramatically increasing the amount of information that could be stored and processed. Qubits can be electrons, nuclei, or photons, among others. In her research, Mikkelsen studies electrons and their potential as qubits. She uses quantum dots, which are nanoscale semiconductor structures with spatial confinement in all three dimensions, to measure and manipulate a single electron spin. By measuring the polarization of light reflected off the quantum dot, she can tell the orientation of the spin. Then using an ultrafast optical pulse, she can rotate the spin to any orientation. She’s also done research on how to prepare, or initialize, electron qubits to receive and transmit information. While physicists have already designed and built working qubits, she says, “One of the main challenges is how to scale things up—to connect multiple qubits together.” She’s interested in experimenting with circuits that use photons rather than electricity to connect qubits. In addition to being faster and able to hold more data, quantum computers could transfer data more securely because the act of eavesdropping would change the nature of the qubits. As Mikkelsen says, “It would allow for completely secure communication; if someone looks at it from the outside, it’s destroyed.” Mikkelsen is also interested in other kinds of nanoscience, optics, photonics, and materials science, all of which offer fruitful areas for exploration at the intersection of physics and engineering. As a child, Mikkelsen says she was fascinated with trying to understand how the world works, and became interested in physics even before high school. That curiosity has never waned. “I love doing the experiments,” she says. “I do very hands-on, table-top experiments—it’s like a great playground.” Mikkelsen visited Duke in June to begin designing her lab. She was heading to Denmark for a visit to her childhood home before returning to UC-Berkeley to wrap up her post-doctoral work, then flying up to Alaska for a two-week vacation. She starts at Duke September 1. “It’s a great environment for quantum computing, photonics, and metamaterials,” she says. Although her research into different aspects of quantum computing certainly has potential practical applications, she says, “It could also go in a lot of different directions that we’re not even imagining right now. It’s both practical and pushing the envelope. To me, it’s fundamentally exciting just to understand how nanoscale quantum mechanical systems really work.”
Mary-Russell Roberson is a freelance science writer who lives in Durham.