Can you tell us about your journey as a scientist so far?
My history with spins and topics related to spin qubits goes back close to 20 years. I did my undergraduate work in a small school called St. Old College in Minnesota, and that’s where I conducted research with a professor who used to work with Norman Ramsey when he was a PhD student.
After that, I did my PhD at the University of Illinois at Urbana-Champaign and I worked on magnetic resonance force microscopy. This is a way to do magnetic resonance imaging of very tiny things. One way to do that is to use a mechanical resonator to detect the force from nuclear spins experiencing magnetic resonance. I explored how to use nanowires as mechanical oscillators to detect nuclear magnetic resonance. I continued as a postdoc at Harvard in the field of semiconductor spin qubits, and I joined the University of Rochester in the Physics department in 2016.
Can you tell us about your current research activities? What are you working on at the moment?
My current research covers a variety of topics related to semiconductor quantum dots and spin qubits, with a particular focus on quantum computing. One of these topics is making spin qubits better - how to improve the design, fabrication, and control. That’s what I like to call the nuts and bolts aspects of semiconductor spin qubits.
In recent work, we explored mechanical resonators as potential systems to interact with semiconductor spin qubits. Another particularly exciting topic is the electrical noise in quantum dots. Noise in nanoscale systems is a longstanding interest of mine, and my PhD was devoted to this topic. In very small groups of nuclear spins, the random statistical polarization exceeds the polarization caused by applying a magnetic field. When you do magnetic resonance imaging of very small systems, one of the main signals you look for is the signal from this randomly occurring polarization of the nuclear spins. Noise is kind of a “dirty business”, but it’s important and we don’t really know too much about it.
What excites you about working with spin qubits and on quantum computing?
Spin qubits have two important advantages related to the goals of quantum computing - and the potential that these bring to the field excites me about working on the topic.
One advantage is that they're very small semiconductor devices compatible with semiconductor manufacturing techniques. A universal, fault-tolerant quantum computer will require thousands or even millions of qubits. With semiconductor qubits, we can make use of the existing expertise in advanced semiconductor manufacturing to imagine making a 300 millimeter wafer full of these qubits.
The other advantage is the possibility of extremely long coherence times. Semiconductor spin qubits can have coherence times that are orders of magnitude longer than other solid-state qubits. This can allow us to achieve very high gate fidelities.
What do you think is the biggest challenge for spin-based quantum computing?
Despite the fact that semiconductor qubits look a lot like transistors and share many of the same manufacturing processes, we use them in a very different way. We use them to confine individual electrons as opposed to turning a current on and off. Making these kinds of qubits reliably and in large numbers is one of the largest challenges in the field. We need to figure out how to make qubits that work consistently well in large devices. When we can do this, it will be a big moment that will move the field of quantum computing forward.
How does the Zurich Instruments HDAWG support your research? Can you tell us more about that?
Setting up a quantum computing research group is technically challenging, but is also expensive. Before we purchased the HDAWG, we were using instruments that were much more expensive than the HDAWG. Now, we have all of the capabilities that we need for a much smaller price, which is also something that helps us with scaling up these kinds of systems.
We're also interested in using the programming capabilities of the HDAWG to make creating and compiling the pulses we need much more efficient. Generating the pulses that we use for semiconductor spin qubits can be quite complicated, and finding ways to efficiently create and upload them is a daily challenge that a lot of different groups have. That's one of the things that we're excited about with the HDAWG.
Changing the tone a little bit, could you tell us an interesting fact about yourself or your team?
When we have our group lunch every Monday, I often start the conversation by asking the team, “What's your favorite something?”, like “What's your favorite color?” or something like that. Last week I changed it up a little bit and I said, “What is your least favorite vegetable?” We ended up with a fun conversation with the team’s least favorite vegetables. I don't want to disclose too much, but all I'll say is that eggplant does not have a good reputation in our team! I like to think we have a really nice group, and if anyone reading the interview wants to work with us eventually, come and get in touch! I think it's a great environment to work in.
