Detection of Sub-Shot-Noise Spatial Correlation in High-Gain Parametric Down Conversion

Università degli Studi dell'Insubria, Varese, Lombardy, Italy
Physical Review Letters (Impact Factor: 7.51). 01/2005; 93(24):243601. DOI: 10.1103/PhysRevLett.93.243601
Source: PubMed


Using a 1 GW, 1 ps pump laser pulse in high-gain parametric down conversion allows us to detect sub-shot-noise spatial quantum correlation with up to 100 photoelectrons per mode by means of a high efficiency charge coupled device. The statistics is performed in single shot over independent spatial replica of the system. Evident quantum correlations were observed between symmetrical signal and idler spatial areas in the far field. In accordance with the predictions of numerical calculations, the observed transition from the quantum to the classical regime is interpreted as a consequence of the narrowing of the down-converted beams in the very high-gain regime.

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    • "Studying these fluctuations involves the use of cameras and needed so far the use of several images to exhibit quantum features. The sub shot-noise nature of the correlation between twin images issued from spontaneous down-conversion has been demonstrated either for a mean of several photons per pixel with low noise charge coupled devices [4] [5] or in the photon-counting regime with electron-multiplying charge coupled devices (EMCCD) [6]. These correlations were subsequently used to improve imaging [7]. "
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    • "PHYSICAL REVIEW X 5, 031004 (2015) 2160-3308=15=5(3)=031004(10) 031004-1 Published by the American Physical Society limited to producing correlations between twin beams (two-mode squeezed state) [15] [16] [17] rather than producing a single squeezed beam. Another workaround is the direct engineering of overlapping squeezed modes [18], but practical scalability is also lacking. "
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    • "In addition, macropixels of each beam known as coherence areas[27] are correlated pairwise across the beams, as shown in Fig. 1. In the limit that each coherence area could be described by a single spatial mode, and if each pair were isolated and the intensity difference measured , the quantum noise reduction would approach that of Eq. 2. A spatially resolving detector, such as a split photodiode, essentially performs this measurement when properly aligned. "
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