# Engineering Quantum Coherence

Tuesday, October 25, 2011 – 3:00pm

Reiss 502

Christopher Lobb

Joint Quantum Institute and Department of Physics, University of Maryland

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 a 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. 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 problems with a Josephson qubit is that it interacts strongly with its 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.

Host: Paola Barbara

Discussion Leader: Paola Barbara