Entanglement Thresholds of Doubly Parametric Quantum Transducers.

Doubly parametric quantum transducers, such as electro-optomechanical devices, show promise for providing the critical link between quantum information encoded in highly disparate frequencies such as in the optical and microwave domains. This technology would enable long-distance networking of superconducting quantum computers. Rapid experimental progress has resulted in impressive reductions in decoherence from mechanisms such as thermal noise, loss, and limited cooperativities.

High-accuracy photoreceiver frequency response measurements at 1.55 µm by use of a heterodyne phase-locked loop.

We demonstrate a high-accuracy heterodyne measurement system for characterizing the magnitude of the frequency response of high-speed 1.55 µm photoreceivers from 2 MHz to greater than 50 GHz. At measurement frequencies below 2 GHz, we employ a phase-locked loop with a double-heterodyne detection scheme, which enables precise tuning of the heterodyne beat frequency with an RF synthesizer.

Analyzing quantitative light scattering spectra of phantoms measured with optical coherence tomography.

We demonstrate the ability of multiple forms of optical coherence tomography (OCT) in the frequency domain to quantitatively size scatterers. Combined with a variety of distinct phantoms, we gain insight into the measurement uncertainties associated with using scattering spectra to size scatterers. We size spherical scatterers on a surface using swept-source OCT with an analysis based on a simple slab-mode resonance model.

Spectroscopic phase-dispersion optical coherence tomography measurements of scattering phantoms.

We demonstrate a novel technique to determine the size of Mie scatterers with high sensitivity. Our technique is based on spectral domain optical coherence tomography measurements of the dispersion that is induced by the scattering process. We use both Mie scattering predictions and dispersion measurements of phantoms to show that the scattering dispersion is very sensitive to small changes in the size and/or refractive index of the scatterer.