Quantum computing and condensed matter physics with microwave photons

Nanowire Superinductance Fluxonium Qubit

T. M. Hazard, A. Gyenis, A. Di Paolo, A. T. Asfaw, S. A. Lyon, A. Blais, and A.A. Houck

Disordered superconducting materials provide a new capability to implement novel circuit designs due to their high kinetic inductance. Here, we realize a fluxonium qubit in which a long NbTiN nanowire shunts a single Josephson junction. We explain the measured fluxonium energy spectrum with a nonperturbative theory accounting for the multimode structure of the device in a large frequency range. Making use of multiphoton Raman spectroscopy, we address forbidden fluxonium transitions and observe multilevel Autler-Townes splitting.

Hyperbolic Lattices in Circuit Quantum Electrodynamics

Alicia J. Kollar, Mattias Fitzpatrick, Andrew A. Houck

After close to two decades of research and development, superconducting circuits have emerged as a rich platform for both quantum computation and quantum simulation. Lattices of superconducting coplanar waveguide (CPW) resonators have been shown to produce artificial materials for microwave photons, where weak interactions can be introduced either via non-linear resonator materials or strong interactions via qubit-resonator coupling.

Interacting Qubit-Photon Bound States with Superconducting Circuits

Neereja Sunaresan, Rex Lundgren, Guanyu Zhu, Alexey Gorshkov, and Andrew A. Houck

Qubits strongly coupled to a photonic crystal give rise to many exotic physical scenarios, beginning with single and multi-excitation qubit-photon dressed bound states comprising induced spatially localized photonic modes, centered around the qubits, and the qubits themselves. The localization of these states changes with qubit detuning from the band-edge, offering an avenue of in situ control of bound state interaction.

Observation of a Dissipative Phase Transition in a One-Dimensional Circuit QED Lattice

Mattias Fitzpatrick, Neereja Sundaresan, Andy C. Y. Li, Jens Koch, and A. A. Houck

Condensed matter physics has been driven forward by significant experimental and theoretical progress in the study and understanding of equilibrium phase transitions based on symmetry and topology. However, nonequilibrium phase transitions have remained a challenge, in part due to their complexity in theoretical descriptions and the additional experimental difficulties in systematically controlling systems out of equilibrium.

Quantum Electrodynamics Near a Photonic Band-Gap

Yanbing Liu and Andrew A. Houck

Photonic crystals provide an extremely powerful toolset for manipulation of optical dispersion and density of states, and have thus been employed for applications from speelautomaten photon generation to quantum sensing with NVs and atoms.

Suppresion of Photon Shot Noise Dephasing in a Tunable Coupling Superconducting Qubit

Gengyan Zhang, Yanbing Liu, James J. Raftery, and Andrew A. Houck

We demonstrate the suppression of photon shot noise dephasing in a superconducting qubit by eliminating its dispersive coupling to the readout cavity. This is achieved in a tunable coupling qubit, where the qubit frequency and coupling rate can be controlled independently. We observe that the coherence time approaches twice the relaxation time and becomes less sensitive to thermal photon noise when the dispersive coupling rate is tuned from several MHz to 22 kHz.