QDev Seminar: Michael Manfra

Pushing GaAs to the extreme: from the 5/2 FQHE to spin qubits

The high mobility two-dimensional electron gas (2DEG) confined in GaAs/AlGaAs heterostructures is a model system for the discovery of unique phases of electronic matter. The study of topological phases which now permeates condensed matter physics has its origin in attempts to understand behavior in the 2DEG at high magnetic fields in the quantum Hall regime.  It is speculated that specific topological states in the quantum Hall regime may find utility in a special flavor of quantum computation protected against decoherence.  I will describe how we actually create such systems using molecular beam epitaxy and how each experiment places unique demands on the design and operation of the underlying heterostructure.  Our recent efforts to understand the role of residual disorder, ever present in real samples, have led to some surprising results that we believe have important consequences for topological quantum computing. The 2DEG in GaAs is also a playground for mesoscopic physics in which individual electrons are isolated in quantum dots.  These structures are the foundation of spin-based quantum bits.  I will describe our effort to understand and mitigate charge noise which is known to limit the fidelity of 2 qubit gate operations.