KNI Special Seminar with Dr. Christian Haffner

"Novel Pockels materials beyond lithium niobate and barium titanate for quantum electro-optical applications"

Christian Haffner, Ph.D.

Wednesday, May 7, 2025 @ 12 pm in 125 Steele

*Light refreshments served after

with introductions by John G Braun Professor of Applied Physics and Physics Dr. Oskar Painter

Abstract

Quantum computers face many challenges towards upscaling the number of qubits and increasing their computational power. For superconducting qubits, this is the radio frequency (RF) -bottleneck between the qubit processor inside the cryostat and the room temperature control and readout electronics.

And like for their classical counterparts, hope lies in replacing the RF-links by optical fibers, resulting in a hybrid situation where RF-qubits will be used for computation and optical qubits will serve for remote communication. However, electro-optical (EO) transducers that parametrically amplify RF-qubits directly to optical qubits with a unity efficiency have thus far remained elusive. Key to a unity efficiency are materials that feature low losses, strong nonlinearities and that allow to squeeze down the electro-magnetic field to smallest volumes. Current research focuses on devices based on opto-electro-mechanics or on lithium niobate devices - the classical workhorse of long-range optical communication. In this talk, we discuss high-k strontium titanate as a potential new material that features nonlinearities (Pockels coefficint of ~350pm/V) larger than any other materials, its unique challenges for EO-transduction and our progress on thin-film integration [1].

[1] Ulrich, A. et al. Engineering high pockels coefficients in thin-film strontium titanate for cryogenic quantum electro-optic applications. arXiv preprint (2025).https://doi.org/10.48550/arXiv.2502.14349

Bio

Christian Haffner is a Principal Member of Technical Staff and the first one to receive IMEC's tenure track. His tenure project investigates the fundamental limits of electro-optical devices for classical and quantum applications. In 2022, he received an ERC starting grant to support this research. In 2019, he joined the 5-year Branco-Weiss Fellowship program. He did his Postdoc research on nano-scale opto-mechanical switches at NIST, Gaithersburg and ETH, Zurich. He earned his Ph.D. degree from ETH Zurich in 2018, which was recognized with the ETH Medal and Hans-Eggenberger Prize. He received his B.Sc. and M.Sc. degree in electrical engineering from the Karlsruhe Institute of Technology (Germany) in 2012 and 2013.