Bichromatic local oscillator for detection of two-mode squeezed states of light

Abstract

We present a new technique for the detection of two-mode squeezed states of light that allows for a simple characterization of these quantum states. The usual detection scheme, based on heterodyne measurements, requires the use of a local oscillator with a frequency equal to the mean of the frequencies of the two modes of the squeezed field. As a result, unless the two modes are close in frequency, a high-frequency shot-noise-limited detection system is needed. We propose the use of a bichromatic field as the local oscillator in the heterodyne measurements. By the proper selection of the frequencies of the bichromatic field, it is possible to arbitrarily select the frequency around which the squeezing information is located, thus making it possible to use a low-bandwidth detection system and to move away from any excess noise present in the system.

Experimental study of a phase-sensitive heterodyne detector

“…III, we extend the theoretical analysis to the case of heterodyne detection with a bichromatic local oscillator. With the orthodox understanding of image sideband vacuum noise, we show that a 3 dB noise penalty should occur in the heterodyne detection, in agreement with a previous work [26] studying heterodyne detection in a similar configuration. Then we show that the heterodyne detector in the studied configuration is indeed phase sensitive and, hence, should be free of noise penalty on the contrary, according to the quantum theory of linear amplifier [25].…”

“…represents the theoretical dilemma faced by the existing quantum theory of optical detection, regarding the quantum noise of a BLO heterodyne detector. performance with a bichromatic local oscillator in the context of the current detection theory: (Table I): On one hand, a 3 dB noise penalty is expected for the detector due to the presence of the image sideband vacuum modes [26]. On the other hand, however, the detector should be noise free at the quantum level because of its phase-sensitive nature [25].…”

Observation of Localized Multi-Spatial-Mode Quadrature Squeezing

“…A homodyne detector using a single-frequency LO at ω 0 would reveal the squeezing around an analysing frequency of ≈ 3 GHz. Instead we use a bichromatic local oscillator (BLO) as proposed by Marino et al [29], where the single frequency component is replaced by two frequency components, one for each of the probe and conjugate sidebands.…”

Lifting the bandwidth limit of optical homodyne measurement with broadband parametric amplification

“…Two independent homodyne measurements of the signal and idler quadratures, x s,i , y s,i need to be made relative to two correlated LOs at their respective frequencies ω s , ω i so that the two output homodyne signals are within the electrical bandwidth. Thus, the standard procedure to measure just a single-frequency component of the two-mode quadrature x ( ω ) (and its squeezing) requires two separate homodyne measurements of the independent quadratures of both the signal and the idler using a pair of phase-correlated LOs 17 , 28 . For a broadband spectrum, standard two-mode homodyne requires a dense set of correlated pairs of LOs for each frequency component of the measurement.…”