Two-Carrier Scheme: Evading the 3 dB Quantum Penalty of Heterodyne Readout in Gravitational-Wave Detectors

Abstract

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Frequency-resolved optical mode decomposition of multimode quantum fields

“…The mode basis is loaded onto the multifrequency components of the classical LO, where one pair of the frequencies that are symmetric with respect to the central frequency of the signal field is modulated by one temporal mode function. Thus, the balanced heterodyne detection using this LO is free of LO excess noise [12,14] and 3 dB quantum noise penalty [16,21]. The multifrequency heterodyne current carries the baseband signal of the quantum field in all the frequency components, and it is separated by a multichannel receiver.…”

“…Since the above monochromatic-LO heterodyne has extra 3 dB noise compared to the homodyne [16] due to the vacuum fluctuation of the image band field [17], the bichromatic-LO heterodyne was proposed and proven to be free of this noise theoretically [9,16,18] and experimentally [19]. This scheme has recently been applied to detection of the broadband quadrature squeezing [20] and to the heterodyne readout in gravitational-wave detectors [21].…”