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Conference on Lasers and Electro-Optics

Single-shot detection of spatial quantum correlation in high-gain parametric down-conversion

Ottavia Jedrkiewicz, A. Gatti, E. Brambilla, Morten Bache, Luigi A. Lugiato, P. Di Trapani, Yun-Kun Jiang

Published Jan 1, 2004• 0 citations
Publisher

Abstract

Using a 1GW-1ps pump-laser pulse in parametric down-conversion allows for single-shot detection of spatial quantum correlation with up to hundreds of photons per mode. The statistics is performed over independent spatial replica of the system.
DOI
10.1364/iqec.2004.imk4

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Parametric down-conversion converts pump photons in pairs of correlated signal and idler photons. Even when pumped by a single-mode laser, the signal and idler photons are spread over several thousand spatial modes yet strongly correlated with each other in their position and transverse momentum. These correlations enable applications in imaging, sensing, communication, and optical processing. Here we show that, using a photon number resolving camera, spatial correlations can be observed after only a few 10s seconds measurement time. Photon number resolving camera technologies are likely to find wide use in quantum enhanced low-light imaging systems.
Cameras with single-photon sensitivities can be used to measure the spatial correlations between the photon-pairs that are produced by parametric down-conversion. Even when pumped by a single-mode laser, the signal and idler photons are typically distributed over several thousand spatial modes yet strongly correlated with each other in their position and anti-correlated in their transverse momentum. These spatial correlations enable applications in imaging, sensing, communication, and optical processing. Here we show that, using a photon-number resolving camera, spatial correlations can be observed after only a few 10s of seconds of measurement time, thereby demonstrating comparable performance with previous single photon sensitive camera technologies but with the additional capability to resolve photon-number. Consequently, these photon-number resolving technologies are likely to find wide use in quantum, low-light, imaging systems.
The ability to efficiently characterize the spatial correlations of entangled states of light is critical for applications of many quantum technologies such as quantum imaging. Here, we demonstrate highly efficient theoretical and experimental characterization of the spatial Schmidt modes and the Schmidt spectrum of bright multiphoton entangled states of light produced from high-gain parametric down-conversion. In contrast to previous studies, we exploit the approximate quasihomogeneity and isotropy of the signal field and dramatically reduce the numerical computations involved in the experimental and theoretical characterization procedures. In our particular case where our experimental datasets consist of 5000 single-shot images of $256\ifmmode\times\else\texttimes\fi{}256$ pixels each, our method reduced the overall computation time by 2 orders of magnitude. This speedup would be even more dramatic for larger input sizes. Consequently, we are able to rapidly characterize the Schmidt modes and the Schmidt spectrum for a range of pump amplitudes and study their variation with increasing gain. Our results clearly reveal the broadening of the Schmidt modes and the narrowing of the Schmidt spectrum for increasing gain with agreement between theory and experiment.