Quantum Research Seminar: Evi Aspropotamiti & Antonio Manesco
Speaker: Antonio Manesco, CMT
Title: Using the electron spin for protected superconducting qubits
Abstract: In superconducting qubits, improving lifetimes often comes at the cost of increased sensitivity to other decoherence channels. Here, I propose to avoid this tradeoff by encoding quantum information in states that belong to disjoint sectors of the Hilbert space. I will introduce a superconducting qubit design in which circuit states are entangled with the spin of a deliberately trapped quasiparticle—turning a typically detrimental excitation into a resource for protection.
Abstract: In superconducting qubits, improving lifetimes often comes at the cost of increased sensitivity to other decoherence channels. Here, I propose to avoid this tradeoff by encoding quantum information in states that belong to disjoint sectors of the Hilbert space. I will introduce a superconducting qubit design in which circuit states are entangled with the spin of a deliberately trapped quasiparticle—turning a typically detrimental excitation into a resource for protection.
Speaker: Evi Aspropotamiti, Quantum Optics
Title: Quantum Effects of a Single Spin on a Mechanical Resonator
Abstract: Mechanical resonators can exhibit long coherence times, interact with nearby systems, and couple efficiently to light. Together, these properties make them a versatile platform for studying light–matter effects and probing the influence of a nearby quantum system, such as a two-level system (TLS), using light as a direct readout of the interaction. Such optomechanical and spin–mechanical platforms can be used for force sensing, transduction, and quantum memory. Importantly, a coupled TLS can also provide the nonlinearity needed to generate non-classical states of mechanical motion. In the theoretical platform we consider, the ground-state spin of a single nitrogen-vacancy (NV) center acts as an effective TLS and is coupled to a membrane resonator with a small attached magnet. The motion of the membrane modulates the magnetic field at the spin position via the field gradient, allowing the spin to sense the mechanical oscillation. In this work, we investigate the feasibility of sensing the effect of a single spin on a resonator in the presence of thermal noise. We then explore the possibility of cooling the resonator using the TLS, and finally examine how the generation of non-classical states, specifically Schrödinger cat states, can be enhanced by mechanical squeezing.
About the Quantum Research Seminar:
The Quantum Research Seminar (QRS) is a student-led monthly seminar series featuring talks from early career researchers in quantum science at KU. It takes place every second Friday of the month from 12-13 in HCØ. Free lunch is provided.
The goal of the QRS is to bring together the quantum community at KU and provide a space for PhDs and PostDocs to practice presenting their research to a wider audience within quantum sciences.