Amos M. Smith

Truly unentangled photon pairs without spectral filtering

We demonstrate that an integrated silicon microring resonator is capable of efficiently producing photon pairs that are completely unentangled; such pairs are a key component of heralded single-photon sources. A dual-channel interferometric coupling scheme can be used to independently tune the quality factors associated with the pump and signal and idler modes, yielding a biphoton wavefunction with a Schmidt number arbitrarily close to unity. This will permit the generation of heralded single-photon states with unit purity.

Ultraviolet integrated photonic circuits (Conference Presentation)

Quantum information processing relies on the fundamental property of quantum interference, where the quality of the interference directly correlates to the indistinguishability of the interacting particles. The creation of these indistinguishable particles, photons in this case, has conventionally been accomplished with nonlinear crystals and optical filters to remove spectral distinguishability, albeit sacrificing the number of photons. This research describes the use of an integrated aluminum nitride microring resonator circuit to selectively generate photon pairs at the narrow cavity transmissions, thereby producing spectrally indistinguishable photons. These spectrally indistinguishable photons can then be routed through optical waveguide circuitry, concatenated interferometers, to manipulate and entangle the photons into the desired quantum states. Photon sources and circuitry are only two of the three required pieces of the puzzle. The final piece which this research is aimed at interfacing with are trapped ion quantum memories, based on trapped Ytterbium ions. These ions serve as very long lived and stable quantum memories with storage times on the order of 10’s of minutes, compared with photonic quantum memories which are limited to 10-6 to 10-3 seconds. The caveat with trapped ions is the interaction wavelength of the photons is 369.5nm and therefore the goal of this research is to develop entangled photon sources and circuitry in that wavelength regime to interact directly with the trapped ions and bypass the need for frequency conversion.

A multipli-entangled photon source for cluster state generation

This paper expands upon prior work on an entangled photon source generating six pairs of photons via spontaneous parametric down-conversion in a single pass configuration. Experimental results measuring entangled photons at 810 nm are shown and other wavelength regimes will be discussed. The design and fabrication considerations for a group velocity matched (GVM) superlattice photon source are discussed. An application of this source enables various multiqubit cluster states to be generated in a compact unidirectional configuration. This configuration simplifies the interferometric stability for any associated feed-forward methods required in photon-based quantum logic circuitry.