Dartmouth Events

Physics and Astronomy Quantum Nano Seminar

Sarah Sheldon, Institute for Quantum Computing/IBM

Thursday, November 14, 2013
Wilder 202
Intended Audience(s): Public
Categories: Lectures & Seminars

Title: "Optimal Control in Open Quantum Systems: Selecting DNP Pathways"

Abstract: High fidelity control is necessary for the future of quantum computing. Optimal control theory has been used successfully to numerically optimize control sequences for spin-based systems. Previous control pulse design efforts have primarily optimized pulses to a desired unitary control. Non-unitary dynamics are unavoidable in quantum systems, and, to improve current control techniques, interactions with the environment and stochastic noise processes must be incorporated into pulse design.

This talk will discuss a method of pulse optimization that includes decoherence, including a particular example of engineering control for an open quantum system: selecting transfer pathways in dynamic nuclear polarization. Dynamic nuclear polarization (DNP) is a method of increasing the nuclear spin magnetization in a nuclear magnetic resonance experiment. DNP works by transferring polarization from a coupled electron spin to the nuclear spin. As the electron thermal polarization is two or three orders of magnitude higher than nuclear polarizations, this can result in a significant increase in the nuclear spin signal. In solid state systems, however, there are multiple pathways through which polarization can be transferred. Excitation of more than one pathway can prevent the nuclear spin from achieving the maximum possible polarization. I have demonstrated in this work that optimal control theory (OCT) can be used to design pulses which will select one pathway and suppress the others. The pulses were found considering the open quantum system dynamics.

I will also talk briefly about designing OCT pulses for tuned NMR probes that including transient effects of the resonator.

For more information, contact:
Tressena Manning

Events are free and open to the public unless otherwise noted.