Quantum Walk Topology and Spontaneous Parametric Down Conversion

In a recent detailed research program we proposed to study the complex physics of topological phases by an all optical implementation of a discrete-time quantum walk. The main novel ingredient proposed for this study is the use of non-linear parametric amplifiers in the network which could in turn be used to emulate intra-atomic interactions and thus analyze many-body effects in topological phases even when using light as the quantum walker. In this paper, and as a first step towards the implementation of our scheme, we analize the interplay between quantum walk lattice topology and spatial correlations of bi-photons produced by spontaneous parametric down-conversion. We also describe different detection methods suitable for our proposed experimental scheme.Comment: 7 pages, 3 figures. arXiv admin note: substantial text overlap with arXiv:1409.127

Laser frequency offset locking scheme for high-field imaging of cold atoms

We present a simple and flexible frequency offset locking scheme developed for high-field imaging of ultra-cold atoms which relies on commercially available RF electronics only. The main new ingredient is the use of the sharp amplitude response of a home-made RF filter to provide an error signal for locking the lasers. We were able to offset lock two independent diode lasers within a capture range of 200 MHz, and with a tuning range of up to 1.4GHz. The beat-note residual fluctuations for offset locked lasers are below 2MHz for integration times of several hundreds of seconds.Comment: 5 Pages, 7 Figure

Entanglement engineering and topological protection by discrete-time quantum walks

Discrete-time quantum walks (QWs) represent robust and versatile platforms for the controlled engineering of single particle quantum dynamics, and have attracted special attention due to their algorithmic applications in quantum information science. Even in their simplest 1D architectures, they display complex topological phenomena, which can be employed in the systematic study of topological quantum phase transitions [1]. Due to the exponential scaling in the number of resources required, most experimental realizations of QWs up to date have been limited to single particles, with only a few implementations involving correlated quantum pairs. In this article we study applications of quantum walks in the controlled dynamical engineering of entanglement in bipartite bosonic systems. We show that quantum walks can be employed in the transition from mode entanglement, where indistinguishability of the quantum particles plays a key role, to the standard type of entanglement associated with distinguishable particles. We also show that, by carefully tailoring the steps in the QWs, as well as the initial state for the quantum walker, it is possible to preserve the entanglement content by topological protection. The underlying mechanism that allows for the possibility of both entanglement engineering and entanglement protection is the strong "spin-orbit" coupling induced by the QW. We anticipate that the results reported here can be employed for the controlled emulation of quantum correlations in topological phases.Comment: 11 Pages, 8 Figures, Invited contribution to J. Phys. B - 20th Anniversary of quantum state engineering special issu