Physics (Internal)

Building quantum materials with superconducting circuits

This event is part of the Biophysics/Condensed Matter Seminar Series.

Superconducting artificial atoms are created by connecting Josephson junctions, which are nonlinear, non-dissipative elements, to simple electrical circuits. Individual artificial atoms can be coupled using this same toolbox of inductors, capacitors, and Josephson junc- tions to build novel quantum materials. In this talk, I will discuss prospects for using the fluxonium artificial atom as a building block for topological materials. Topological phases of matter have excitations with exotic quantum statistics and have been proposed as a plat- form for robust quantum computation. Building a topological material from the bottom-up, however, requires individual components with degenerate ground states and strong coupling between these components. I will describe two circuits based on the fluxonium artificial atom that meet these require- ments. The first circuit is an artificial molecule composed of two strongly-coupled fluxonium artificial atoms, which realizes a Hamiltonian with a dominant σz σz -type interaction between the individual atoms [1]. We find excellent agreement between the measured spectroscopy of the circuit and the theoretically-predicted level transitions, which highlights the suitability of superconducting circuits for implementing tailored quantum systems. Instead of the cos ϕ energy term characteristic of a Josephson junction, the second circuit realizes an unconven- tional cos 2ϕ energy term, which results in a nearly-degenerate ground-excited state manifold. Taken together, these circuits fulfill the requirements for the building blocks of topological phases and we can thus start to realize topological materials using superconducting circuits.

[1] A. Kou, et al., arxiv:1610.01094 (2016).