Dr. Amrit Poudel, Dartmouth College
Title: "Relaxation in Quantum Dots Due to Evanescent-Wave Johnson Noise From Metallic Gates"
Abstract: This talk will present a study of decoherence in charge and spin qubits due to evanescent-wave Johnson noise (EWJN) in a laterally coupled double quantum dot and single quantum dot, respectively. The high density of evanescent modes in the vicinity of metallic gates causes energy relaxation and a loss of phase coherence of electrons trapped in quantum dots. These energy relaxation rates are derived, and EWJN is shown to be a dominant source of decoherence for spin qubits held at low magnetic fields. Our approach goes beyond the dipole approximation and remedies the unphysical divergence by taking into account the finite size of the quantum dot. The effect of nonlocal dielectric response of thin metallic films will also be discussed. Remarkably, the fluctuations responsible for decoherence of charge qubits from a thin film are greatly enhanced over the case of a conducting half space.
Time permitting, I will also consider another interesting topic about the dynamics of a spin coupled to its environment in a slowly rotating magnetic field and discuss its implication on the experimental measurement of the Berry curvature using non-adiabatic control protocol.
Events are free and open to the public unless otherwise noted.