Events at Physics |
Events on Friday, August 7th, 2026
- Preliminary Exam
- Qubit control in Si/SiGe: Hopping based single qubit gates
- Time: 10:30 am - 12:30 pm
- Place: 5310 Chamberlin
- Speaker: Minyoung Kim, Physics PhD Graduate Student
- Abstract: Control of spin qubits in Si/SiGe is conventionally achieved through electric dipole spin resonance (EDSR), which requires a high-frequency driving field and the accompanying heating that limits gate performance. An alternative is the hopping gate, in which an electron is shuttled between two quantum dots whose quantization axes are non-parallel, so that a universal gate is assembled from a sequence of wait times rather than by resonant driving. In this talk, I will present a systematic analysis of hopping-based universal single-qubit gates and their implementation in the Wiggle Well, a Si/SiGe heterostructure with oscillating Ge concentration which enhances intrinsic spin orbit coupling and couples the tilt angle between quantization axes to the valley phase of each dot. Because a physical ramp between charge configurations takes finite time, the evolution is decomposed into an idealized rotation and a residual "kick" operator, whose components can be extracted experimentally from hopping oscillations and then compensated. Simulations including Landau-Zener leakage, hyperfine fields from residual Si, Ge isotopes, and charge noise map the resulting infidelity landscape as a function of magnetic field and ramp time, identifying the regime in which high fidelity hopping gates are achievable. Related work on tunnl-and valley-coupling measurment in double quantum dots and ongoing noise correlation spectroscopy with excahnge-only qubits will also be discussed.
- Host: Benjamin Woods