Observation of an effect due to non-stationary shot noise

S. Chua, Kirk McKenzie, B. C. Buchler +1 more

We present an experimental investigation into non-stationary events that occur in a homodyne detection system. The importance of non-stationary events is that it is a possible mechanism preventing shot-noise-limited homodyne detection at low frequencies, a necessary condition that needs to be routinely fulfilled in order to detect squeezed states at these frequencies. These non-stationary events are thought to arise due to airborne dust passing through the laser beam paths. We show that these non-stationary events which occur in our laboratory environment can be minimised by placing the experiment in an airtight enclosure. Isolation against non-stationary events achieved improvement of the colour of the noise spectrum by 3dB at 10Hz towards a flat shot noise spectrum and improvement in the noise distribution of the signal towards a Gaussian distribution.

Marc de Jong

Michael Stefszky, Conor M Mow-Lowry, S. Chua +7 more

The advent of stable, highly squeezed states of light has generated great interest in the gravitational wave community as a means for improving the quantumnoise- limited performance of advanced interferometric detectors. To confidently measure these squeezed states, it is first necessary to measure the shot-noise across the frequency band of interest. Technical noise, such as non-stationary events, beam pointing, and parasitic interference, can corrupt shot-noise measurements at low Fourier frequencies, below tens of kilo-Hertz. In this paper we present a qualitative investigation into all of the relevant noise sources and the methods by which they can be identified and mitigated in order to achieve quantum noise limited balanced homodyne detection. Using these techniques, flat shot-noise down to Fourier frequencies below 0.5 Hz is produced. This enables the direct observation of large magnitudes of squeezing across the entire audio-band, of particular interest for ground-based interferometric gravitational wave detectors. 11.6 dB of shot-noise suppression is directly observed, with more than 10 dB down to 10 Hz.

D. B. Horoshko, S. Ya. Kilin

M S Stefszky, C M Mow-Lowry, S. Chua +7 more

The advent of stable, highly squeezed states of light has generated great interest in the gravitational wave community as a means for improving the quantumnoise- limited performance of advanced interferometric detectors. To confidently measure these squeezed states, it is first necessary to measure the shot-noise across the frequency band of interest. Technical noise, such as non-stationary events, beam pointing, and parasitic interference, can corrupt shot-noise measurements at low Fourier frequencies, below tens of kilo-Hertz. In this paper we present a qualitative investigation into all of the relevant noise sources and the methods by which they can be identified and mitigated in order to achieve quantum noise limited balanced homodyne detection. Using these techniques, flat shot-noise down to Fourier frequencies below 0.5 Hz is produced. This enables the direct observation of large magnitudes of squeezing across the entire audio-band, of particular interest for ground-based interferometric gravitational wave detectors. 11.6 dB of shot-noise suppression is directly observed, with more than 10 dB down to 10 Hz.

Hai Wang, Qing Pan, Yun Zhang +3 more