Colloquium: Prof. Xuedong Hu, University of Buffalo
Location
Physics : 401
Date & Time
October 15, 2014, 3:30 pm – 4:30 pm
Description
TITLE: Decoherence of a non-equilibrium spin qubit
ABSTRACT: Recent experimental and theoretical research on spin qubits in quantum dots have clearly demonstrated that spins have long coherence times and can be reliably controlled. Our current theoretical understanding of spin coherence is based completely on a confined but otherwise free spin. Here I discuss our recent efforts in characterizing decoherence of spin qubits that are being manipulated. In one project, we study electron spin decoherence when the quantum dot is in motion. We find that the motion induced spin decoherence is a pure longitudinal relaxation channel, whose rate depends on the disorder in the substrate, the strength of the magnetic field, and the speed of the quantum dot motion. In another project, we study decoherence of a spin qubit that is field driven. We find that the driving modifies the bath for the spin so that its decoherence properties could be significantly changed. These two studies show that putting a spin qubit in a non-equilibrium situation almost always introduce modifications to its environment, therefore causing its decoherence properties to change, sometimes for the better, sometimes for the worse.
We thank support by US ARO and NSF PIF.
ABSTRACT: Recent experimental and theoretical research on spin qubits in quantum dots have clearly demonstrated that spins have long coherence times and can be reliably controlled. Our current theoretical understanding of spin coherence is based completely on a confined but otherwise free spin. Here I discuss our recent efforts in characterizing decoherence of spin qubits that are being manipulated. In one project, we study electron spin decoherence when the quantum dot is in motion. We find that the motion induced spin decoherence is a pure longitudinal relaxation channel, whose rate depends on the disorder in the substrate, the strength of the magnetic field, and the speed of the quantum dot motion. In another project, we study decoherence of a spin qubit that is field driven. We find that the driving modifies the bath for the spin so that its decoherence properties could be significantly changed. These two studies show that putting a spin qubit in a non-equilibrium situation almost always introduce modifications to its environment, therefore causing its decoherence properties to change, sometimes for the better, sometimes for the worse.
We thank support by US ARO and NSF PIF.