In the race of post-CMOS computing technologies, coherent information processing with microwave circuits have demonstrated great potentials with the recent breakthrough in quantum computing, where both the quanta and the phase of the excitation states can be utilized for carrying and processing information. As one of the candidate excitations for coherent information processing, magnons are collective excitations of exchange-coupled spins in magnetic materials with the natural frequency lying in the microwave regime. Compared with other excitations, magnons exhibit special advantages: 1) their frequency can be noninvasively tuned by an external magnetic field, 2) they can couple to various excitations for coherent transduction and multitasking capabilities, and 3) they possess abundant dynamic properties, such as nonlinearity, for processing and manipulating microwave excitations. Furthermore, magnetic materials can be easily fabricated as nanodevices while still serving as excellent magnon resonators, which is convenient for on-chip integration and device miniaturization. In this seminar I will explore the use of coherent magnon dynamics for novel information processing techniques. In the first case , we realize strong coupling between magnons in a permalloy (Ni80Fe20) thin-film device to the microwave photons in a coplanar superconducting resonator, where strong coupling strengths up to sub-gigahertz are realized along with high cooperativity thanks to the high quality factor and small mode volume of the superconducting resonator. In the second case , we demonstrate coherent excitation of Rabi-like oscillations of magnons in a nanomagnet in the deeply nonlinear regime, which provides new approaches to modify magnon populations with long coherence. I will also discuss their links and potentials in quantum information processing.
Dr. Yi Li is currently a postdoc in Argonne National Laboratory. He has obtained his B.S. degree in Physics from Peking University (2009) and his Ph.D. degree in Materials Science & Engineering from Columbia University (2015). Prior to Argonne he has been a postdoc at CEA Saclay in France for two years (2015-2017). Yi Li's research focuses on microwave superconducting circuits, magnetic nanodevices and their hybrid systems and their applications in quantum information science.