Hi everybody, we’ll be giving talks at Caltech May 11th and 12th. Here is some information:
May 11: IQI Seminar
Richard Harris, D-Wave
3:00 pm, 107 Annenberg
Title: Experimental investigation of an eight qubit unit cell in a superconducting optimization processor
A superconducting chip containing a regular array of flux qubits, tunable interqubit inductive couplers, an XY-addressable readout system, on-chip programmable magnetic memory, and a sparse network of analog control lines has been studied. The architecture of the chip and the infrastructure used to control it were designed to facilitate an adiabatic quantum optimization algorithm. The performance of an eight-qubit unit cell on this chip has been characterized by measuring its success in solving a large set of random Ising spin glass problems as a function of processor temperature. The experimental data are consistent with the predictions of a quantum mechanical model of an eight-qubit system coupled to an environment in thermal equilibrium. These results highlight many of the key practical challenges that we have overcome and those that lie ahead in the quest to realize a functional large scale adiabatic quantum information processor. This lecture will be partitioned as follows:
Part I will provide a detailed overview of the processor design, fabrication, and operation.
Part II will focus upon experimental results and numerical simulations.
May 12: IQI Special Seminar
Mohammad Amin, D-Wave
TBD, time and location
Title: Distinguishing classical from quantum annealing in a multi-qubit system
Use of quantum annealing to find the ground state of engineered spin glasses has been proposed as a more effective alternative to classical simulated annealing for solving some types of hard combinatorial optimization problems. Where classical annealing employs progressively weaker thermal fluctuations to avoid entrapment in local potential energy minima, quantum annealing seeks to use progressively weaker quantum fluctuations and tunneling. Both classical and quantum annealing result in final probability distributions that depend upon annealing rate and temperature. Having obtained such a probability distribution through an annealing process, one may ask whether it has been reached via quantum or classical annealing. To answer this question, it is necessary to find a measurable or testable property that clearly distinguishes the two. In this presentation, I explain how the time at which the dynamics of the system stop, the “freeze-out point”, can play such a role. The temperature dependence of such a dynamical freeze-out time is completely different for classical and quantum annealing process. I suggest a procedure to probe this freeze-out time, and present experimental data for a single qubit and a chain of 8 ferromagnetically coupled qubits. I then compare the data with theoretical predictions of classical and quantum models, and show that our data clearly exhibit the signature of a quantum annealing process. At the end I provide details of our classical and quantum models and explain how the parameters are extracted from independent experiments.