# Condensed Matter Seminar

Christopher Lobb, University of Maryland

http://www.umdphysics.umd.edu/index.php/about-us/people/faculty/169-lobb.html

"Engineering quantum coherence"

RSA (Rivest, Shamir and Adleman) encryption is commercially used for everything from A (Amazon.com) to B (banking) and beyond. RSA’s security is based on the mathematical difficulty of factoring a large number; a sufficiently large number can overwhelm the most powerful classical computer. In 1994, Peter Shor published an efficient factoring algorithm based on quantum computational principles. Since then, a number of different schemes for building qubits, the basic elements of quantum computers, have been proposed and studied to exploit this quantum efficiency. In this talk, I will discuss qubits based on Josephson junctions. Josephson qubits are made using integrated-circuit techniques, so that they have the advantage of scalability—if you can fabricate one junction on a chip, you can fabricate millions. The problem with a Josephson qubits is that they interact strongly with the environment, which causes loss of the quantum coherence needed to operate as qubits. I will show how a variety of engineering tools, from circuit design to materials optimization, can improve the performance of Josephson qubits while also improving our understanding of the boundaries between the quantum and the classical worlds.