We study a physical system consisting of a Bose-Einstein condensate confined to a ring shaped lattice potential interrupted by three weak links. The system is assumed to be driven byan effective flux piercing the ring lattice. By employing path integral techniques, we explore the effective quantum dynamics of the system in a pure quantum phase dynamics regime. Complementarily, the effects of the density’s quantum fluctuations are studied through exact diagonalization analysis of the spectroscopy of the Bose-Hubbard model. We demonstrate that a clear two-level system emerges by tuning the magnetic flux at degeneracy. The lattice confinement, platform for the condensate, is realized experimentally employing a spatial light modulator.
We introduce a simple method to realize and detect photonic topological Chern insulators with one-dimensional circiut quantum electrodynamics arrays. By periodically modulating thecouplings of the array, we show that this one-dimensional model can be mapped into a two-dimensional Chern insulator model. In addition to allow the study of photonic Chern insulators, this approach also provides a natural platform to realise experimentally Laughlin’s pumping argument. Based on scattering theory of topological insulators and input-output formalism, we show that the photonic edge state can be probed directly and the topological invariant can be detected from the winding number of the reflection coefficient phase.
Fast quantum gates based on geometric phases provide a platform for performing robust quantum computation. In particular, non-adiabatic holonomic quantum computation, which involvesnon-Abelian geometric phases to achieve universality, has recently been demonstrated in several experiments. Here, we generalize the transitionless quantum driving algorithm to a degenerate Hilbert space, with which we propose a route towards fast holonomic quantum computation. We propose a proof-of-principle experiment in a superconducting circuit architecture to realize our scheme.
We propose to construct large quantum graph codes by means of superconducting circuits working at the ultrastrong coupling regime. In this physical scenario, we are able to create acluster state between any pair of qubits within a fraction of a nanosecond. To exemplify our proposal, creation of the five-qubit and Steane codes are demonstrated. We also provide optimal operating conditions with which the graph codes can be realized with state-of-the-art superconducting technologies.
Quantum networks play an important role in the implementation of quantum computing, communication and metrology. Circuit quantum electrodynamics (QED), consisting of superconductingartificial atoms coupled to on-chip resonators, provides a prime candidate to implement these networks due to their controllability and scalability. Furthermore, recent advances have also pushed the technology to the ultrastrong coupling (USC) regime of light-matter interaction, where the qubit-cavity coupling strength reaches a considerable fraction of the cavity frequency. Here, we propose the implementation of a scalable quantum random-access memory (QRAM) architecture based on a circuit QED network, whose edges operate in the USC regime. In particular, we study the storage and retrieval of quantum information in a parity-protected quantum memory and propose quantum interconnects in experimentally feasible schemes. Our proposal may pave the way for novel quantum memory applications ranging from entangled-state cryptography, teleportation, purification, fault-tolerant quantum computation, to quantum simulations.