Quantum Enhanced Balanced Heterodyne Readout for Differential Interferometry
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Updated: Jun 15, 2025

Quantum State Engineering of Light with Continuous-wave Optical Parametric Oscillators
Published on: May 30, 2014
Daniel W Gould1, Vaishali B Adya2, Sheon S Y Chua1
1OzGrav, Centre for Gravitational Astrophysics, Research School of Physics and Research School of Astronomy and Astrophysics, <a href="https://ror.org/019wvm592">Australian National University</a>, Australian Capital Territory, Australia.
Abstract:
Conventional heterodyne readout schemes are now under reconsideration due to the realization of techniques to evade its inherent 3 dB signal-to-noise penalty. The application of high-frequency, quadrature-entangled, two-mode squeezed states can further improve the readout sensitivity of audio-band signals. In this Letter, we experimentally demonstrate quantum-enhanced heterodyne readout of two spatially distinct interferometers with direct optical signal combination, circumventing the 3 dB heterodyne signal-to-noise penalty. Applying a high-frequency, quadrature-entangled, two-mode squeezed state, we show further signal-to-noise improvement of an injected audio band signal of 3.5 dB. This technique is applicable for quantum-limited high-precision experiments, with application to searches for quantum gravity, searches for dark matter, gravitational wave detection, and wavelength-multiplexed quantum communication.
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