"Nonlinear Quantum Dynamics in a Disordered Magnet" by Thomas Rosenbaum (Caltech)

Thursday, May 2, 2019 - 4:00pm to 5:00pm
Physics and Astronomy Colloquium

Thursdays, 4:00-5:00 pm

1-434 Physics and Astronomy (map)
Reception from 3:45-4:00 p.m.
 (unless otherwise posted)

Guest Speaker: Thomas F. Rosenbaum (Caltech)

Talk Title:  “Nonlinear Quantum Dynamics in a Disordered Magnet”


Quantum memories depend on encodable, yet minimally-interacting, degrees of freedom. We study a model quantum magnet, Li(Ho,Y)F4, where Ho dipoles in the dilute limit form clusters of several hundred spins that bind together and can be excited resonantly. By analogy to laser excitation of atoms, we use a pump-probe magnetic technique to drive the system out of the linear regime, and study both the nature of the excitations and the coupling of the excitations to the spin bath. By applying a magnetic field transverse to the Ising axis, we are able to tune the dynamics of the quantum degrees of freedom such that localized clusters (the “qubits”) essentially decouple from their environment. In the second part of the talk, I will discuss the case of increased dipole concentration where the ground state of the system is an ordered ferromagnet. In this limit, we drive the system hard and study the magnetic domain dynamics through Barkhausen noise. We characterize the statistics of the magnetic avalanches and reveal the effects of quantum fluctuations on the non-equilibrium response. Together, these experiments demonstrate the new states and new insights that can be derived by driving a quantum system away from equilibrium.


For more information, contact Yaroslav Tserkovnyak

We thank the following people for their contributions to the wine fund for the post-colloquium reception:
Professors Katsushi Arisaka, Andrea Ghez, Karoly Holczer, Huan Huang, HongWen Jiang, Per Kraus, Alexander Kusenko, Matthew Malkan, Mayank Mehta, Warren Mori, Ni Ni, Seth Putterman, David Saltzberg, Yaroslav Tserkovnyak, Vladimir Vassiliev, Shenshen wang, and Nathan Whitehorn.



1-434 PAB