Notable Alumni | Andreas Weichselbaum Models Quasiparticles That Could Be Future of Quantum Computing

Editor’s Note: The College of Arts & Sciences Notable Alumni Awards honor alumni for broad career accomplishments, commitment to community service, and valuable contributions to 51�� and the College of Arts & Sciences.

Dr. Andreas Weichselbaum holds his notable alumni award with faculty from the College of Arts & Sciences — Andreas Weichselbaum, ’04 Ph.D. Physics receives an 51�� Notable Alumni Award. Bottom to top of stairs, left to right: Dean Florenz Plassmann, Dr. Andreas Weichselbaum, Dr. Sergio E. Ulloa, Dr. Arthur Smith, Dr. Michael P. Jensen, Dr. David C. Ingram

Andreas Weichselbaum ’04 Ph.D. Physics

is working on tiny correlated puzzles in material science that could have a giant impact on the future of computing.

Weichselbaum is a theoretical physicist in the field of condensed matter and strongly correlated systems.

In a recent collaboration, for example, he and a team at and Germany proposed a novel theoretical method for producing more robust Majorana fermions. Splitting one electron in half results in a linked pair of Majorana quasiparticles, and the correlation of the linked particles could become a foundation for quantum computing.

“In other words, an electron becomes an entangled (linked) pair of two Majorana quasiparticles, with the link persisting regardless of the distance between them,” Brookhaven reports in .

Dr. Andreas Weichselbaum, ’04 Ph.D. Physics

Weichselbaum was honored when he came to OHIO to present an NQPI Seminar on “” on Feb. 13.

Dr. Andreas Weichselbaum and colleagues in front of a whiteboard — Theoretical calculations performed by (left to right) Neil Robinson, Robert Konik, Alexei Tsvelik, and Andreas Weichselbaum of Brookhaven Lab’s Condensed Matter Physics and Materials Science Department suggest that Majorana fermions exist in the boundaries of magnetic materials with different magnetic phases. Majorana fermions are particle-like excitations that emerge when single electrons fractionalize into two halves, and their unique properties are of interest for quantum applications.

“Scientists hope to use Majorana fermions that are physically separated in a material to reliably store information in the form of qubits, the building blocks of quantum computers. The exotic properties of Majoranas—including their high insensitivity to electromagnetic fields and other environmental ‘noise’—make them ideal candidates for carrying information over long distances without loss.

“The team plans to follow up their theoretical study with experiments using engineered systems such as quantum dots (nanosized semiconducting particles) or trapped (confined) ions. Compared to the properties of real materials, those of engineered ones can be more easily tuned and manipulated to introduce the different phase boundaries where Majorana fermions may emerge,” the article continues.

In 2018, Weichselbaum joined the of Brookhaven National Laboratory as a staff scientist.

Class photo of physics students from 2004 — Andreas Weichselbaum (back row, yellow shirt) in a group photo of physics students.

He earned a Ph.D. in Physics from the College of Arts & Sciences at 51��. His focus was in theoretical condensed matter physics, with his thesis on “Nanoscale quantum dynamics and electrostatic coupling.”

After OHIO, he accepted a postdoc position at the Ludwig-Maximilians Universität in Munich in Germany. In 2008 he joined the University of California at Irvine as a visiting researcher before heading back to Munich for a habilitation (venia docendi). He was an independent researcher since 2011, and was awarded a Heisenberg Fellowship in 2015 funded by , the German research foundation. His work included research in computational condensed matter theory and large-scale computational projects on cutting edge research (strongly correlated systems).

“My continued focus has been on the numerical simulation of nanostructures. Starting with my postdoc, I had moved into the field of strongly correlated systems, using numerical renormalization group techniques to study nanosystems embedded in dissipative environments” he writes .

“Quantum-many-body systems in and out of equilibrium in the presence of interaction offer many interesting open questions, given that strong correlation can lead to new emergent dynamical effects such as Kondo physics. In their exploration, besides analytical approaches, the access to quasi-exact numerical methods provides an extremely valuable perspective.”

OHIO Memories

“I very much learned to appreciate the diverse and international atmosphere at 51��. Arriving as a bunch of new grad students from all over the world for an academic year, one naturally became a rather tight community as one started to find one’s way together around that endeavor commonly referred to as doctoral studies, irrespective of where one was coming from,” Weichselbaum notes. “My most cherished memories from that time belong to the very welcome frequent dinner invites from Indian fellow students and dear friends which were always a wonderful way to unwind at the end of a long day. Below is a picture of a party crowd at their place.”

Andreas Weichselbaum and friends sit on the floor of a student's house — Andreas Weichselbaum and friends

Andreas Weichselbaum, a friend, and a young child sit by the pond in Emeriti Park — Andreas Weichselbaum enjoying the greenery on the OHIO campus, frequently taking coffee breaks at the pond outside Clippinger.

Weichselbaum, in cap and gown, with his parents — Andreas Weichselbaum with his parents at graduation

“I am very grateful that also my parents could make it to OhioU for the commencement ceremony at the end of my Ph.D., their only time ever traveling to the United States,” Weichselbaum added.

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