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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    ABSTRACT: Spatially entangled twin photons provide a test of the Einstein-Podolsky-Rosen (EPR) paradox in its original form of position (image plane) versus impulsion (Fourier plane). We show that recording a single pair of images in each plane is sufficient to safely demonstrate an EPR paradox. On each pair of images, we have retrieved the fluctuations by subtracting the fitted deterministic intensity shape and then have obtained an intercorrelation peak with a sufficient signal to noise ratio to safely distinguish this peak from random fluctuations. A 95% confidence interval has been determined, confirming a high degree of paradox whatever the considered single pairs. Last, we have verified that the value of the variance of the difference between twin images is always below the quantum (poissonian) limit, in order to ensure the particle character of the demonstration. Our demonstration shows that a single image pattern can reveal the quantum and non-local behavior of light.
    Optics Express 10/2015; 23(20):26472-26478. DOI:10.1364/OE.23.026472 · 3.49 Impact Factor
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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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    ABSTRACT: Quantum states of light can improve imaging whenever the image quality and resolution are limited by the quantum noise of the illumination. In the case of a bright illumination, quantum enhancement is obtained for a light field composed of many squeezed transverse modes. A possible realization of such a multi-spatial-mode squeezed state is a field which contains a transverse plane in which the local electric field displays reduced quantum fluctuations at all locations, on any one quadrature. Using a traveling-wave amplifier, we have generated a multi-spatial-mode squeezed state and showed that it exhibits localized quadrature squeezing at any point of its transverse profile, in regions much smaller than its size. We observe 75 independently squeezed regions. The amplification relies on nondegenerate four-wave mixing in a hot vapor and produces a bichromatic squeezed state. The result confirms the potential of this technique for producing illumination suitable for practical quantum imaging.
    Physical Review X 07/2015; 5(3):031004. DOI:10.1103/PhysRevX.5.031004 · 9.04 Impact Factor
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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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