UChicago PME Quantum Colloquium - Charles Marcus

Classical complex systems are often characterized by many nearly degenerate states 
separated by barriers forming a complex energy landscape. We examine complexity as it 
arises in a quantum mechanical context, in the form of arrays of Josephson junctions. By 
realizing JJ arrays in superconductor-semiconductor hybrids we can tune devices through 
the superconductor-insulator transition — a quantum phase transition in two dimensions — 
using electrostatic gates, like a transistor, and explore the interaction of complexity and 
quantum coherence and uncertainty. Finally, I speculate on the computational difficulty of 
solving these problems.