#QUSTEC Portrait: A pure mathematics lover doing industrial research

For Daniel Miller, it all started with his love for pure mathematics and in particular linear algebra. Turning his attention to quantum information theory was a logical consequence since, unlike other fields of theoretical physics, this one is heavy on linear algebra rather than calculus or other mathematical subdisciplines.

Miller started his journey into quantum information theory early on and even co-authored five scientific papers all while completing degrees in physics and mathematics at the Heinrich Heine University in Düsseldorf. Little did he know back then that this road would lead him straight into one of the most exciting places to do industrial quantum information research with tangible results that go far beyond the research lab. Now at IBM Research, Miller is helping shape the future of computing with quantum computers as one of its fundamental building blocks.

In his publications as an undergraduate student, Miller explored devices such as quantum repeaters which could help build a future quantum internet by compensating for the loss of photons over long distances in quantum networks. He also looked into the important issue of quantum error correction, a pre-requisite for the long-term goal of building a useful universal quantum computer. Miller’s research on quantum error correction has already been used in the first demonstration of a complete quantum error correction code. And he even ventured into the field of quantum cryptography, which deals with the use of quanta of light, photons, to secure communications.

After obtaining his two master’s degrees, Miller was looking for inspiring PhD projects. And he quickly found a good fit for his interests and skills in the Quantum Technology group at the IBM Research Europe lab in Rüschlikon near Zurich. His position is part of the QUSTEC program, which connects young quantum scientists at the universities of Basel, Freiburg, Strasbourg, as well as the Karlsruhe Institute of Technology, the Walther Meissner Institute near Munich, and IBM Research.

“IBM Research is highly renowned in the quantum computing community. With my background in quantum information theory, IBM Research in Zürich is the best place in Europe for me to do my PhD. I hope to broaden my expertise to quantum chemistry and hole spin qubits in silicon quantum dots”, Miller says.

Entering now the field of quantum chemistry, Miller is thrilled to contribute towards the solutions of some of the biggest challenges for quantum algorithms. “There are two holy grails in quantum chemistry that could be reached with quantum computers. The first is developing a catalyst for ammonia synthesis by simulating the active center of the nitrogenase enzyme, which solves this problem in plants. The second holy grail is room-temperature superconductivity.”

In addition to his new adventure with quantum chemistry, Miller is using his PhD as an opportunity to explore new routes on the hardware side of quantum computing. His focus lies on hole spin qubits in silicon quantum dots within the national center of competence SPIN funded by the Swiss National Science Foundation. “The most advanced quantum computing platforms today are superconducting qubits and trapped ions. Spin qubits are less mature but have potential advantages and thus may be able to catch up and maybe even take over eventually”, Miller says. He notes, however, that this is a long-term vision that won’t be reached within the limited time frame of his own PhD project.

Starting his PhD in the middle of the pandemic has of course posed challenges. “Due to the lockdown, I am lacking the daily exchanges with my more experienced colleagues. I have seen my productivity drop significantly following the permanent home office mandate”, says Miller. However, he does not give up: “I try to limit the damage by using this time in isolation to continue working on a research paper based on the topic of my Master’s thesis. And in this spring semester I am trying to complete all online courses that are a pre-requisite for obtaining my doctoral degree. That will spare me the commute to the University of Basel when they switch back to on-campus courses.”

When he’s not busy with tough mathematical riddles, Miller spends time cultivating his passion for music, which for him means everything from singing to playing the piano or the ukulele. Miller is happy that his PhD project brought him to Switzerland: “I really enjoy what this country has to offer in terms of natural beauty, the vast outdoors and the peacefulness of the Alps.”

Leonid Leiva Ariosa / IBM

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