arXiv subjects

Paul A. Altin

Publications and source records attributed to Paul A. Altin.

4 recordsLinked to original sources

arXiv2018

Observation of squeezed light in the 2 $\mathrm{μm}$ region

We present the generation and detection of squeezed light in the 2 $\mathrm{μm}$ wavelength region. This experiment is a crucial step in realising the quantum noise reduction techniques that will be required for future generations of gravitational-wave detectors. Squeezed vacuum is generated via degenerate optical parametric oscillation from a periodically-poled potassium titanyl phosphate crystal, in a dual resonant cavity. The experiment uses a frequency stabilised 1984 nm thulium fibre laser, and squeezing is detected using balanced homodyne detection with extended InGaAs photodiodes. We have measured $4.0 \pm 0.1$ dB of squeezing and $10.5 \pm 0.5$ dB of anti-squeezing relative to the shot noise level in the audio frequency band, limited by photodiode quantum efficiency. The inferred squeezing level directly after the optical parametric oscillator, after accounting for known losses and phase noise, is 10.7 dB.

physics.ins-det↗

arXiv2015

Thermal noise of gram-scale cantilever flexures

We present measurements of thermal noise in niobium and aluminium flexures. Our measurements cover the audio frequency band from 10Hz to 10kHz, which is of particular relevance to ground-based interferometric gravitational wave detectors, and span up to an order of magnitude above and below the fundamental flexure resonances at 50Hz - 300Hz. Our results are well-explained by a simple model in which both structural and thermoelastic loss play a role. The ability of such a model to explain this interplay is important for investigations of quantum-radiation-pressure noise and the standard quantum limit.

physics.ins-det↗

arXiv2014

A Bright Solitonic Matter-Wave Interferometer

We present the first realisation of a solitonic atom interferometer. A Bose-Einstein condensate of $1\times10^4$ atoms of rubidium-85 is loaded into a horizontal optical waveguide. Through the use of a Feshbach resonance, the $s$-wave scattering length of the $^{85}$Rb atoms is tuned to a small negative value. This attractive atomic interaction then balances the inherent matter-wave dispersion, creating a bright solitonic matter wave. A Mach-Zehnder interferometer is constructed by driving Bragg transitions with the use of an optical lattice co-linear with the waveguide. Matter wave propagation and interferometric fringe visibility are compared across a range of $s$-wave scattering values including repulsive, attractive and non-interacting values. The solitonic matter wave is found to significantly increase fringe visibility even compared with a non-interacting cloud.

quant-ph↗

arXiv2005

Through Einstein's Eyes

We have developed a relativistically-accurate computer graphics code and have used it to produce photo-realistic images and videos of scenes where special relativistic effects dominate, either in astrophysical contexts or in imaginary worlds where the speed of light is only a few metres per second. The videos have been integrated into our under-graduate teaching programme for several years. Recently we took the next step, encouraging undergraduate students to use the code to explore relativity, develop their own videos, and eventually package them together into Through Einstein's Eyes, a multimedia CD.

physics.ed-ph↗