Quantum computing and condensed matter physics with microwave photons

Beyond Strong Coupling in a Massively Multimode Cavity

Neereja M. Sundaresan, Yanbing Liu, Darius Sadri, Laszlo J. Szocs, Devin L. Underwood, Moein Malekakhlagh, Hakan E. Tureci, Andrew A. Houck

The study of light-matter interaction has seen a resurgence in recent years, stimulated by highly controllable, precise, and modular experiments in cavity quantum electrodynamics (QED). The achievement of strong coupling, where the coupling between a single atom and fundamental cavity mode exceeds the decay rates, was a major milestone that opened the doors to a multitude of new investigations. Here we introduce multimode strong coupling (MMSC), where the coupling is comparable to the free spectral range (FSR) of the cavity, i.e.

Observation of a Dissipation-Induced Classical to Quantum Transition

James Raftery, Darius Sadri, Sebastian Schmidt, Hakan E. Türeci, Andrew A. Houck

The emergence of non-trivial structure in many-body physics has been a central topic of research bearing on many branches of science. Important recent work has explored the non-equilibrium quantum dynamics of closed many-body systems. Photonic systems offer a unique platform for the study of open quantum systems. We report here the experimental observation of a novel dissipation driven dynamical localization transition of strongly correlated photons in an extended superconducting circuit.

Time-reversal symmetrization of spontaneous emission for quantum state transfer

Srikanth J. Srinivasan, Neereja M. Sundaresan, Darius Sadri, Yanbing Liu, Jay M. Gambetta, Terri Yu, S. M. Girvin, and Andrew A. Houck

We demonstrate the ability to control the spontaneous emission from a superconducting qubit coupled to a cavity. The time domain profile of the emitted photon is shaped into a symmetric truncated exponential. The experiment is enabled by a qubit coupled to a cavity, with a coupling strength that can be tuned in tens of nanoseconds while maintaining a constant dressed state emission frequency. Symmetrization of the photonic wave packet will enable use of photons as flying qubits for transfering the quantum state between atoms in distant cavities.

A scanning transmon qubit for strong coupling circuit quantum electrodynamics

William E. Shanks, Devin L. Underwood, Andrew A. Houck

Like a quantum computer designed for a particular class of problems, a quantum simulator enables quantitative modeling of quantum systems that is computationally intractable with a classical computer. Quantum simulations of quantum many-body systems have been performed using ultracold atoms and trapped ions among other systems.

Circuit quantum electrodynamics with a spin qubit

K. D. Petersson, L. W. McFaul, M. D. Schroer, M. Jung, J. M. Taylor, A. A. Houck & J. R. Petta

Electron spins trapped in quantum dots have been proposed as basic building blocks of a future quantum processor. Although fast, 180-picosecond, two-quantum-bit (two-qubit) operations can be realized using nearest-neighbour exchange coupling, a scalable, spin-based quantum computing architecture will almost certainly require long-range qubit interactions.

Symmetries and collective excitations in large superconducting circuits

David G. Ferguson, A. A. Houck, Jens Koch

The intriguing appeal of circuits lies in their modularity and ease of fabrication. Based on a toolbox of simple building blocks, circuits present a powerful framework for achieving new functionality by combining circuit elements into larger networks. It is an open question to what degree modularity also holds for quantum circuits -- circuits made of superconducting material, in which electric voltages and currents are governed by the laws of quantum physics.