Northwestern Events Calendar


PAECRS: Shih-Yuan Chen and Matthew Capocci

When: Wednesday, May 15, 2024
12:30 PM - 1:30 PM CT

Where: Technological Institute, F160, 2145 Sheridan Road, Evanston, IL 60208 map it

Audience: Faculty/Staff - Student - Post Docs/Docs - Graduate Students

Contact: Joan West   (847) 491-3645

Group: Physics and Astronomy PAECRS

Category: Academic


"Rocking, Rolling, and Jumping: How an Excited Liquid Marble Dances on a Flat Stage"

Shih-Yuan Chen, PhD Student

Liquid marbles are water drops wrapped with hydrophobic powder (materials that dislike water). The powder shell prevents the liquid marble from directly contacting a substrate and allows the marble to move easily. In this talk, I will demonstrate a new mechanism to manipulate a specific type of liquid marble made of ferrofluid, a liquid containing nano-size magnetic particles, so we can deform and control the marble's motion by applying an external magnetic field. Our experimental results show that when we apply a rotational magnetic field with constant field strength, the drop elongates and rolls along the direction of the field. Moreover, we discover a new phase of motion – jumping, as we further increase the field strength. We observed that the marble's motion resembled that of a rolling ellipse, which adjusted its angular velocity to compensate for changes in curvature; accompanying it is the change of the kinetic energy. Consequently, a rolling marble starts jumping once its kinetic energy overcomes its weight. In fact, we can even control the marble to jump uphill under the right conditions. This mechanism to drive the liquid marble offers a novel approach to studying the interaction between multiple liquid marbles, and provides a new way for liquid transportation.


"Limits to Driving in Superconducting Circuits"

Matthew Capocci, PhD Candidate

Superconducting qubits are a promising candidate for realizing quantum computing. Scaling devices to include more qubits is crucial to this goal and one way to do so is using quantum modules of qubits coupled via a driven coupler. Driven nonlinear systems, such as transmons and SNAILs, provide interactions between qubits coupled to them. This makes them great candidates to use as a coupler as they can perform single- and multi-qubit gates by driving the coupler directly. These systems offer modularity, scalability, and flexibility in fabrication, but they suffer from long gate times due to the weak coupling between the qubits and the coupler, leading to fidelities limited by qubit coherence times. These long gate times can be addressed by increasing the drive strength. However, driving the couplers above a certain drive strength threshold leads to breakdown in the qubits. This has been found both experimentally and numerically, and in this presentation, the explanation as to how this arises and the mechanism behind it are explained.

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