Interfacing superconducting qubits with light | Johannes Fink (IST Austria)

This Video was recorded on 29 April 2025 as part of the MCQST Colloquium which takes place at ‪@maxplanckquantum‬

Interfacing superconducting qubits with light.
Optical photons propagate with ultra-low loss and do not interact easily, which makes them perfect information carriers both in quantum and classical applications. Logical operations and sensing on the other hand rely on nonlinearities and strong interactions that are typically realized with GHz clock speed electrical circuits. The field of microwave photonics combines these two domains of the electromagnetic spectrum with a diverse set of applications ranging from radar and satellite communication, to radio-over-fiber and remote sensing. At the quantum level however, no equivalent technology exists. This is particularly problematic because quantum systems rely on analog information exchange in a low-noise environment. As a result, quantum microwave circuits - such as superconducting processors and semiconductor spin qubits - so far are restricted to operate inside an isolated space at millikelvin temperatures and without the benefits of quantum photonics and optical fibers, i.e. high bandwidth, high density, low-loss, multiplexed, low thermal conductivity and noise resilient control and communication at room temperature.

Building on our modular electro-optic platform - one of the lowest noise and highest efficiency microwave-optical interconnects to date [1, 2] - we have generated microwave-optical entanglement in the continuous variable domain [3], and demonstrated a circulator-free, all-optical single-shot readout of a superconducting qubit [4] where all required signal conditioning is implemented at room temperature.

In this talk I'll review aspects of these results and then focus on our team's progress and challenges towards entangling superconducting qubits with time-bin encoded telecom wavelength single photon states at room temperature. If time allows, I will also showcase recent experimental progress on novel and unconventional entanglement distribution schemes [5] as well as our progress to coherently control protected superconducting qubit encodings with bit flip times exceeding hours [6] - a possible approach to achieve the coherence times required to realize long-distance quantum networks.

[1] W. Hease*, A. Rueda*, R. Sahu, M. Wulf, G. Arnold, H. G. L. Schwefel, J. M. Fink. PRX Quantum 1, 020315 (2020)
[2] Rishabh Sahu, William Hease, Alfredo Rueda, Georg Arnold, Liu Qiu, Johannes Fink. Nature Commun. 13, 1276 (2022)
[3] Rishabh Sahu*, Liu Qiu*, William Hease, Georg Arnold, Yuri Minoguchi, Peter Rabl, and Johannes M. Fink. Science 380, 718 (2023)
[4] Georg Arnold*, Thomas Werner*, Rishabh Sahu, Lucky N. Kapoor, Liu Qiu, and Johannes M. Fink. Nature Physics (2025)
[5] Joan Agustí, Yuri Minoguchi, Johannes M. Fink, Peter Rabl. Phys. Rev. A 105, 062454 (2022)
[6] Farid Hassani, Matilda Peruzzo, Lucky N. Kapoor, Andrea Trioni, Martin Zemlicka, Johannes M. Fink. Nature Commun. 14, 3968 (2023)


About Johannes Fink
Johannes Fink is a Professor at the Institute of Science and Technology Austria (ISTA). After obtaining a Ph.D. in the field of circuit quantum electrodynamics at ETH Zurich in 2010, he moved on to study mechanical and optical quantum devices as an IQIM postdoc and senior staff scientist at the California Institute of Technology. At ISTA since 2016, he works on integrating superconducting qubit technology with on-chip acoustic and photonic degrees of freedom. His goal is to study quantum devices in new parameter regimes and explore their potential applications in computation, communication and sensing. More info at http://www.quantumids.com

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The MCQST Colloquium Series features interdisciplinary talks given by visiting international speakers. The monthly colloquium covers topics spanning all MCQST research units and is broadcasted live via Zoom for audiences worldwide. The main goal of the series is to create the framework for idea exchange, to strengthen links with QST leading groups worldwide, as well as to act as an integral part of the local educational environment.
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