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Toward non-Gaussian control of ultra-coherent superconducting circuit optomechanics
On September 25, Assistant Prof. Shingo Kono from the Niels Bohr Institute, University of Copenhagen, visited the WMI and gave a seminar talk on superconducting circuit optomechanics. He presented an architecture for ultra-coherent superconducting mechanical membranes, which has enabled millisecond-scale mechanical squeezing, topological optomechanical lattices, and collective ground-state cooling. Looking ahead, he outlined a hybrid approach combining optomechanics with circuit QED as a route toward non-Gaussian quantum control of mechanical motion.
About the speaker
Shingo Kono is an Assistant Professor at the Niels Bohr Institute, University of Copenhagen. He received his PhD from the University of Tokyo in 2019 under the supervision of Yasunobu Nakamura and then worked at RIKEN. As a Marie Skłodowska-Curie fellow in the group of Tobias Kippenberg at EPFL, he studied hybrid systems of electromechanical devices and superconducting quantum circuits.
Researchers at WMI have proposed a new type of laser called a bosonic avalanche laser, where a stream of bosonic particles drives a chain reaction resembling an avalanche. Remarkably, random particle arrivals can generate a highly regular laser output, a phenomenon known as coherence resonance, usually associated with excitable systems such as neurons. Even under extremely weak signals, where quantum fluctuations are large, the device maintains surprisingly regular behavior. By converting single particles into amplified, easily detectable pulses, the system could enable ultra-sensitive quantum sensors. The team also outlines a superconducting-circuit implementation and demonstrates how the technology could function as a single-photon detector for microwave-frequency quantum signals.
Matthias Opel was invited to a MINT Career Information Day, organized by the Humboldt Academy of Science and Engineering (HASE) at the Humboldt-Gymnasium Vaterstetten, Germany. Being one of 22 speakers, he presented his daily life as a senior scientist in low temperature physics in four individual, 45-min sessions with 10 high school students each. Finally, he performed a 30-min show with liquid nitrogen for the general audience in the main auditorium and demonstrated the levitation of a high-Tc (YBa2Cu3O7−δ) superconductor above a permanent magnet.
Researchers at the Walther-Meißner-Institut have shown that cavity electromechanical devices can serve as ultrasensitive sensors for materials research, enabling the detection of individual magnetic flux vortices in a superconducting nanostructure. Cavity electromechanical systems convert minute mechanical displacements into microwave signals and are among the most sensitive motion detectors available today. While they are primarily developed as platforms for quantum technologies, practical sensing applications remain rare.
Using a suspended 30-micrometer-long aluminum nanostring, the researchers exploited attonewton-scale force sensitivity to observe the entry of individual magnetic flux quanta into a superconductor. Such vortices are of considerable interest because they can introduce loss and noise in superconducting devices. By monitoring tiny changes in the nanostring's mechanical resonance frequency, the team resolved signatures of single vortex-entry events. The work demonstrates a new sensing application of cavity electromechanics and provides a powerful tool for studying the formation and dynamics of magnetic flux vortices in superconducting nanostructures.
The WMI contributed to the summer party of the Bavarian Academy of Sciences and Humanities in the Botanical Garden in Munich. Vera Bader and Matthias Opel performed experiments at low temperatures with liquid nitrogen. Matthias discussed the thermal expansion of gases and solids. Vera demonstrated the low viscosity of nitrogen in comparison to water, utilizing a prototypical Bavarian felt hat. Finally, they explained the Meißner-Ochsenfeld effect and showed the levitation of a high-Tc (YBa2Cu3O7−δ) superconductor above a permanent magnet using the superconducting WMI racetrack.
