Two-dimensional Lattice Gauge Theories with Superconducting Quantum Circuits

A quantum simulator of U(1) lattice gauge theories can be implemented with superconducting circuits. This allows the investigation of confined and deconfined phases in quantum link models, and of valence bond solid and spin liquid phases in quantum dimer models. Fractionalized confining strings and the real-time dynamics of quantum phase transitions are accessible as well. Here we show how state-of-the-art superconducting technology allows us to simulate these phenomena in relatively small circuit lattices. By exploiting the strong non-linear couplings between quantized excitations emerging when superconducting qubits are coupled, we show how to engineer gauge invariant Hamiltonians, including ring-exchange and four-body Ising interactions. We demonstrate that, despite decoherence and disorder effects, minimal circuit instances allow us to investigate properties such as the dynamics of electric flux strings, signaling confinement in gauge invariant field theories. The experimental realization of these models in larger superconducting circuits could address open questions beyond current computational capability.

Design and Realization of an Energy Harvester Using Pulsating Arterial Pressure

Most medical implants run on batteries, which require costly and tedious replacement or recharging. It is believed that micro-generators utilizing intracorporeal energy could solve these problems. However, such generators do not, at this time, meet the energy requirements of medical implants.This paper highlights some essential aspects of designing and implementing a power source that scavenges energy from arterial expansion and contraction to operate an implanted medical device. After evaluating various potentially viable transduction mechanisms, the fabricated prototype employs an electromagnetic transduction mechanism. The artery is inserted into a laboratory-fabricated flexible coil which is permitted to freely deform in a magnetic field. This work also investigates the effects of the arterial wall's material properties on energy harvesting potential. For that purpose, two types of arteries (Penrose X-ray tube, which behave elastically, and an artery of a Göttinger minipig, which behaves viscoelastically) were tested. No noticeable difference could be observed between these two cases. For the pig artery, average harvestable power was 42 nW. Moreover, peak power was 2.38 μW. Both values are higher than those of the current state of the art (6 nW/16 nW). A theoretical modelling of the prototype was developed and compared to the experimental results.