arXiv subjects

Keyu Xia

Publications and source records attributed to Keyu Xia.

40 records · Page 3Linked to original sources

arXiv2014

Tunable slowing, storing and releasing of a weak microwave field

We study the slowing, storing and releasing of microwave pulses in a superconducting circuits composed of two coplanar waveguide resonators and a superconducting transmon-type qubit. The quantum interference analogy to electromagnetically induced transparency is created in two coupled resonators. By tuning the resonance frequency of the transmon, we dynamically tune the effective coupling between the resonators. Via the modulation of the coupling, we show the tunable true time delay of microwave pulses at the single-photon level. We also store the microwave field in a high-Q resonator and release the signal from it to the output port. Our scheme promises applications in both quantum information processing and classical wireless communications.

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arXiv2013

Ultrabroadband nonreciprocal transverse energy flow of light in linear passive photonic circuits

Using a technique, analogous to coherent population trapping in an atomic system, we propose schemes to create transverse light propagation violating left-right symmetry in a photonic circuit consisting of three coupled waveguides. The frequency windows for the symmetry breaking of the left-right energy flow span over 80 nm. Our proposed system only uses linear passive optical materials and is easy to integrate on a chip.

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arXiv2013

Deterministic generation of an on-demand Fock state

We theoretically study the deterministic generation of photon Fock states on-demand using a protocol based on a Jaynes Cummings quantum random walk which includes damping. We then show how each of the steps of this protocol can be implemented in a low temperature solid-state quantum system with a Nitrogen-Vacancy centre in a nano-diamond coupled to a nearby high-Q optical cavity. By controlling the coupling duration between the NV and the cavity via the application of a time dependent Stark shift, and by increasing the decay rate of the NV via stimulated emission depletion (STED) a Fock state with high photon number can be generated on-demand. Our setup can be integrated on a chip and can be accurately controlled.

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arXiv2011

Pathway interference in a loop array of three coupled microresonators

A system of three coupled toroidal microresonators arranged in a loop configuration is studied. This setup allows light entering the resonator setup from a tapered fiber to evolve along a variety of different pathways before leaving again through the fiber. In particular, the loop configuration of the resonators allows for an evolution which we term roundtrip process, in which the light evolves from one resonator sequentially through all others back to the initial one. This process renders the optical properties of the system sensitive to the phases of all coupling and scattering constants in the system. We analyze the transmission and reflection spectra, and interpret them in terms of interference between the various possible evolution pathways through the resonator system. In particular, we focus on the phase dependence of the optical properties. Finally, we discuss possible applications for this phase sensitivity induced by the roundtrip process, such as the measurement of the position of a nanoparticle close to one of the resonators, and the measurement of changes in the refractive index between two resonators. Our analytical results for the applications are supported by proof-of-principle calculations based on finite-difference-time-domain solution ofMaxwell's equations in two dimensions on a grid.

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