Energy-participation quantization of Josephson circuits

Superconducting microwave circuits incorporating nonlinear devices, such as Josephson junctions, are a leading platform for emerging quantum technologies. Increasing circuit complexity further requires efficient methods for the calculation and optimization of the spectrum, nonlinear interactions, and dissipation in multi-mode distributed quantum circuits. Here we present a method based on the energy-participation ratio (EPR) of a dissipative or nonlinear element in an electromagnetic mode. The EPR, a number between zero and one, quantifies how much of the mode energy is stored in each element. The EPRs obey universal constraints and are calculated from one electromagnetic-eigenmode simulation. They lead directly to the system quantum Hamiltonian and dissipative parameters. The method provides an intuitive and simple-to-use tool to quantize multi-junction circuits. We experimentally tested this method on a variety of Josephson circuits and demonstrated agreement within several percents for nonlinear couplings and modal Hamiltonian parameters, spanning five orders of magnitude in energy, across a dozen samples.

Dynamic Topology Reconfiguration of Boltzmann Machines on Quantum Annealers

Boltzmann machines have useful roles in deep learning applications, such as generative data modeling, initializing weights for other types of networks, or extracting efficient representations from high-dimensional data. Most Boltzmann machines use restricted topologies that exclude looping connectivity, as such connectivity creates complex distributions that are difficult to sample. We have used an open-system quantum annealer to sample from complex distributions and implement Boltzmann machines with looping connectivity. Further, we have created policies mapping Boltzmann machine variables to the quantum bits of an annealer. These policies, based on correlation and entropy metrics, dynamically reconfigure the topology of Boltzmann machines during training and improve performance.

Introduction

An introduction to long-term climate-neutral energy makes clear that most arises from the Sun or the motions of the Sun-Earth system. Quantum physics is an essential part of understanding the Sun’s energy source, nuclear fusion. The expected depletion times of oil and other fossil fuels are discussed. The most recent 500,000 years of Earth temperature and sea level are surveyed and shown to correlate closely with carbon dioxide levels in the atmosphere. Sea level and temperature are correlated and move together on time scales of five thousand years. The definition of sustainable energy, the topic of this textbook, is very straightforward. This is the energy that will be available on (after) a timescale set by the earliest benchmarks of our civilization, let us say the timescale of the earliest pyramids or the Chinese Wall, visible from space.