IQIM Postdoctoral and Graduate Student Seminar
Thaddeus Ladd is a presently a senior research scientist at HRL Laboratories, LLC in Malibu, CA. Thaddeus began his Hertz-foundation-supported Ph.D. dissertation work on spin-qubit-based quantum computing implementations in the group of Yoshi Yamamoto at Stanford University in 1998. Throughout his career, he has focused on control methods and error models for spin-based qubits in solid-state materials. His thesis work included experimental dynamical decoupling sequences for silicon nuclear spins. He continued post-graduate research at Stanford, holding positions at U. Tokyo and NII, primarily focusing on ultrafast optical control of single spins in self-assembled quantum dots. Upon moving to HRL in 2009, he has worked with a team primarily considering exchange-only control of Si/SiGe quantum dots, but he continues to seek new materials and methods for better qubits.
Abstract: Qubits based on silicon offer the promise of low magnetic noise due to isotopic enhancement and the availability of existing silicon growth and fabrication processes. Triple-dot qubits offer promise of exchange-only spin-qubit control, enabling operation using only gate voltages. The main impediments to silicon qubits are interface disorder, charge noise, valley degeneracy, and nuclear magnetism. In this talk, I will summarize recent data characterizing these impediments for SiGe triple dots fabricated in an undoped accumulation-mode gate architecture, including symmetric barrier control to mitigate charge noise, and isotopic enhancement to mitigate nuclear noise. I will then discuss the mathematics of pulse sequences allowing gauge-independent quantum logic, enabling future developments for exchange-only multiqubit quantum processors.
Updated location for this week's talk: Talk will begin at 12 noon in 201 E. Bridge. Lunch will be available following the talk in 114 E. Bridge.