Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Physical Review Letters

Measurement of Sub-Shot-Noise Correlations of Spatial Fluctuations in the Photon-Counting Regime

Jean-Luc Blanchet, F. Devaux, Luca Furfaro, Éric Lantz

Published Dec 3, 2008• 143 citations
Publisher

Abstract

We have measured sub-shot-noise quantum correlations of spatial fluctuations in the far-field image of the parametric fluorescence created in a type I beta-barium-borate nonlinear crystal. Imaging is performed at very low light level (0.15 photons per pixel) with an electron multiplying charge coupled device camera. Experimental results overcome the standard quantum limit shot-noise level without subtraction of the variance of the detection noise.

DOI
10.1103/physrevlett.101.233604

Related papers

Purely spatial coincidences of twin photons in parametric spontaneous down-conversion

Jean-Luc Blanchet, F. Devaux, Luca Furfaro +1 more

We have measured sub-shot-noise quantum correlations of spatial fluctuations in the far-field image of the parametric fluorescence created in a type I $\ensuremath{\beta}$-barium-borate nonlinear crystal, either between opposite angular sectors (nondegenerate configuration) or between opposite pixels (degenerate configuration). Imaging is performed at a very low light level ($0.2$ photons per pixel) with an electron-multiplying CCD camera, resulting in purely spatial coincidences between single photons when detecting on pixels. Experimental results overcome the standard quantum-limit-shot-noise level without subtraction of the variance of the detection noise. We compare these experimental results with numerical results given by the quantum Green's function method, which is proved to have strong advantages over stochastic simulations.

Physical Review A•Apr 19, 2010•17 citations

Purely spatial coincidences in parametric spontaneous down conversion

Jean-Luc Blanchet, F. Devaux, Luca Furfaro +1 more

Spontaneous down conversion (SPDC) occurs in a nonlinear crystal when a pump photon splits in a pair of signal and idler photons. This paper demonstrates detection of single photons in low light level images with an electron multiplying CCD camera (EMCCD). The opposite spatial fluctuations of SPDC radiation are correlated in the quantum regime. Here, correlations between pixels are presented for collinear phase matching. The far field image of the parametric fluorescence is formed in the focal plane of a lens on a back-illuminated EMCCD. A thresholding procedure is applied on each image, in order to decide whether there is one or zero photo-electron on each pixel. We have experimentally demonstrated that spatial SPDC fluctuations between opposite pixels are quantum correlated in the far field.

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)•Jun 1, 2009•0 citations

Full field measurement of spatial correlated photon pairs with an EMCCD camera

M. Edgar, D. S. Tasca, Frauke Izdebski +5 more

The spatial correlations between the photon pairs produced by spontaneous parametric down conversion (SPDC) have been investigated in a number of different configurations over the last two decades (1). The high dimensionality of the transverse spatial degrees of freedom (DOF) of the photon pairs can be explored either by projections onto a discrete (infinite) basis, such as the LG modes, or by using a continuous basis defined by the transverse position or momentum of the photons. For instance, it has been shown that their transverse position and momentum display EPR-type correlations (2). Despite the continuous and unbounded nature of both these bases, the most common measurements to date have relied upon the scanning of a single avalanche photodiode or a very small number of individual detectors. This sequential scanning or small number of detectors negates any information capacity advantage in the use of spatial states. Recent years have seen a rapid advance in imaging technologies, particularly for low light levels. Of these technologies the highest quantum efficiency is achieved using electron multiplying CCDs (EMCCD). Developments in low noise EMCCD cameras suggest they are capable of greater than 80% quantum efficiencies and if operated in an ultra-low light environment whilst being maintained at low temperatures, can provide single photon sensitivity (3). EMCCDs have been used in measurements of sub-shot-noise correlations of intensity fluctuations (4, 5) as well as in intensity correlations measurements (6) in the far field of the photon pairs from SPDC. Here we report the observation of spatial correlations from SPDC using an EMCCD camera in both the image and far-field planes of the down conversion crystal. We pump a BBO crystal at 355nm with a few milli-Watts of optical power and use a simple lens system to relay the down-converted light to an EMCCD array which can be positioned in either the image plane or the far-field of the crystal. Our photon flux is around 1/100 per pixel, which approximately doubles the signal obtained when the light is blocked. We typically record 100,000 individual frames and then sum the auto-correlation of the individual frames. We observed intensity correlation and anti-correlation in the image and far-field planes, respectively. In both cases we make the correlations more visible by subtracting a background which is obtained as the average correlation obtained between successive frames. Using this approach we are able to visualize the strength of the correlations in both position and momentum, showing a variance product nearly one order of magnitude below the classical limit in both x and y directions.

•Jan 1, 2012•0 citations

Sub-shot noise spatial correlations applied to imaging, metrology and sensing experiments

Ivano Ruo Berchera, Marco Genovese

Istituto Nazionale di Ricerca Metrologica (INRIM), Strada delle Cacce 91, 10135 Torino, Italy. E-mail:i.ruoberchera@inrim.it Quantum correlations of twin beams represent a resource of great importance for the developments of quantum technologies allowing unprecedented results in quantum information, metrology and quantum imaging. Focusing on the measurement of the photon numbers, spatial multimode correlations beyond the shot noise limit have been experimentally demonstrated by using parametric down conversion (PDC) and CCD camera (both at the single photon level and at higher photon flux) [1], and also with other interesting techniques [2]. One of their natural application is the quantum imaging of weak absorbing objects, showed in Fig.1, with sensitivity beyond the shot-noise-level [3]. The idea consists in measuring the intensity pattern on one branch of PDC, where the object has been inserted, and then subtracting the correlated noise pattern measured in the other branch that does not interact with the object. In our presentation we overview the sub-shot noise imaging protocol mentioned above and other applications where the spatial quantum correlation can give some advantages over the classical ones. As an example, we studied the signalto-noise ratio (SNR) of ghost imaging protocols with quantum and classical light [4]. We realized a ghost imaging experiment in the mesoscopic regime (one thousand of photon per pixel per shot), obtaining substantial quantum enhanced performances (see Fig.1). We also demonstrated that spatial quantum correlations provide the possibility for the absolute calibration of analog and/or photon number resolving detectors, providing the first absolute calibration (without any comparison with reference standards, neither optical source nor detector) of a scientific CCD camera [5]. In this first realization we already reached interesting uncertainty level. All these findings indicate that the control and detection of quantum spatial correlation is a rather mature field and other application to different sensing scenarios can be envisaged.

•Jan 1, 2012•1 citation

Sub-shot-noise shadow sensing with quantum correlations

Ermes Toninelli, M. Edgar, Paul‐Antoine Moreau +3 more

The quantised nature of the electromagnetic field sets the classical limit to the sensitivity of position measurements. However, techniques based on the properties of quantum states can be exploited to accurately measure the relative displacement of a physical object beyond this classical limit. In this work, we use a simple scheme based on the split-detection of quantum correlations to measure the position of a shadow at the single-photon light level, with a precision that exceeds the shot-noise limit. This result is obtained by analysing the correlated signals of bi-photon pairs, created in parametric downconversion and detected by an electron multiplying CCD (EMCCD) camera employed as a split-detector. By comparing the measured statistics of spatially anticorrelated and uncorrelated photons we were able to observe a significant noise reduction corresponding to an improvement in position sensitivity of up to 17% (0.8dB). Our straightforward approach to sub-shot-noise position measurement is compatible with conventional shadow-sensing techniques based on the split-detection of light-fields, and yields an improvement that scales favourably with the detector's quantum efficiency.

Optics Express•Aug 29, 2017•20 citations

Observation of spatial quantum correlations in the macroscopic regime

Ashok Kumar, Hayden Nunley, Alberto M. Marino

Spatial quantum correlations in the transverse degree of freedom promise to enhance optical resolution, image detection, and quantum communications through parallel quantum information encoding. In particular, the ability to observe these spatial quantum correlations in a single shot will enable such enhancements in applications that require real-time imaging, such as particle tracking and in situ imaging of atomic systems. Here, we report on measurements in the far field that show spatial quantum correlations in single images of bright twin beams with ${10}^{8}$ photons in a 1-$\ensuremath{\mu}\mathrm{s}$ pulse using an electron-multiplying charge-coupled-device camera. A four-wave mixing process in hot rubidium atoms is used to generate narrowband, bright pulsed twin beams of light. Owing to momentum conservation in this process, the twin beams are momentum correlated, which leads to spatial quantum correlations in the far field. We show around 2 dB of spatial quantum noise reduction with respect to the shot-noise limit. The spatial squeezing is present over a large range of total number of photons in the pulsed twin beams.

arXiv:1611.06445•Physical Review A•May 19, 2017•40 citations
We have measured sub-shot-noise quantum correlations of spatial fluctuations in the far-field image of the parametric fluorescence created in a type I beta-barium-borate nonlinear crystal. Imaging is performed at very low light level (0.15 photons per pixel) with an electron multiplying charge coupled device camera. Experimental results overcome the standard quantum limit shot-noise level without subtraction of the variance of the detection noise.
We have measured sub-shot-noise quantum correlations of spatial fluctuations in the far-field image of the parametric fluorescence created in a type I $\ensuremath{\beta}$-barium-borate nonlinear crystal, either between opposite angular sectors (nondegenerate configuration) or between opposite pixels (degenerate configuration). Imaging is performed at a very low light level (0.20.20.2 photons per pixel) with an electron-multiplying CCD camera, resulting in purely spatial coincidences between single photons when detecting on pixels. Experimental results overcome the standard quantum-limit-shot-noise level without subtraction of the variance of the detection noise. We compare these experimental results with numerical results given by the quantum Green's function method, which is proved to have strong advantages over stochastic simulations.
Spontaneous down conversion (SPDC) occurs in a nonlinear crystal when a pump photon splits in a pair of signal and idler photons. This paper demonstrates detection of single photons in low light level images with an electron multiplying CCD camera (EMCCD). The opposite spatial fluctuations of SPDC radiation are correlated in the quantum regime. Here, correlations between pixels are presented for collinear phase matching. The far field image of the parametric fluorescence is formed in the focal plane of a lens on a back-illuminated EMCCD. A thresholding procedure is applied on each image, in order to decide whether there is one or zero photo-electron on each pixel. We have experimentally demonstrated that spatial SPDC fluctuations between opposite pixels are quantum correlated in the far field.
The spatial correlations between the photon pairs produced by spontaneous parametric down conversion (SPDC) have been investigated in a number of different configurations over the last two decades (1). The high dimensionality of the transverse spatial degrees of freedom (DOF) of the photon pairs can be explored either by projections onto a discrete (infinite) basis, such as the LG modes, or by using a continuous basis defined by the transverse position or momentum of the photons. For instance, it has been shown that their transverse position and momentum display EPR-type correlations (2). Despite the continuous and unbounded nature of both these bases, the most common measurements to date have relied upon the scanning of a single avalanche photodiode or a very small number of individual detectors. This sequential scanning or small number of detectors negates any information capacity advantage in the use of spatial states. Recent years have seen a rapid advance in imaging technologies, particularly for low light levels. Of these technologies the highest quantum efficiency is achieved using electron multiplying CCDs (EMCCD). Developments in low noise EMCCD cameras suggest they are capable of greater than 80% quantum efficiencies and if operated in an ultra-low light environment whilst being maintained at low temperatures, can provide single photon sensitivity (3). EMCCDs have been used in measurements of sub-shot-noise correlations of intensity fluctuations (4, 5) as well as in intensity correlations measurements (6) in the far field of the photon pairs from SPDC. Here we report the observation of spatial correlations from SPDC using an EMCCD camera in both the image and far-field planes of the down conversion crystal. We pump a BBO crystal at 355nm with a few milli-Watts of optical power and use a simple lens system to relay the down-converted light to an EMCCD array which can be positioned in either the image plane or the far-field of the crystal. Our photon flux is around 1/100 per pixel, which approximately doubles the signal obtained when the light is blocked. We typically record 100,000 individual frames and then sum the auto-correlation of the individual frames. We observed intensity correlation and anti-correlation in the image and far-field planes, respectively. In both cases we make the correlations more visible by subtracting a background which is obtained as the average correlation obtained between successive frames. Using this approach we are able to visualize the strength of the correlations in both position and momentum, showing a variance product nearly one order of magnitude below the classical limit in both x and y directions.
Istituto Nazionale di Ricerca Metrologica (INRIM), Strada delle Cacce 91, 10135 Torino, Italy. E-mail:i.ruoberchera@inrim.it Quantum correlations of twin beams represent a resource of great importance for the developments of quantum technologies allowing unprecedented results in quantum information, metrology and quantum imaging. Focusing on the measurement of the photon numbers, spatial multimode correlations beyond the shot noise limit have been experimentally demonstrated by using parametric down conversion (PDC) and CCD camera (both at the single photon level and at higher photon flux) [1], and also with other interesting techniques [2]. One of their natural application is the quantum imaging of weak absorbing objects, showed in Fig.1, with sensitivity beyond the shot-noise-level [3]. The idea consists in measuring the intensity pattern on one branch of PDC, where the object has been inserted, and then subtracting the correlated noise pattern measured in the other branch that does not interact with the object. In our presentation we overview the sub-shot noise imaging protocol mentioned above and other applications where the spatial quantum correlation can give some advantages over the classical ones. As an example, we studied the signalto-noise ratio (SNR) of ghost imaging protocols with quantum and classical light [4]. We realized a ghost imaging experiment in the mesoscopic regime (one thousand of photon per pixel per shot), obtaining substantial quantum enhanced performances (see Fig.1). We also demonstrated that spatial quantum correlations provide the possibility for the absolute calibration of analog and/or photon number resolving detectors, providing the first absolute calibration (without any comparison with reference standards, neither optical source nor detector) of a scientific CCD camera [5]. In this first realization we already reached interesting uncertainty level. All these findings indicate that the control and detection of quantum spatial correlation is a rather mature field and other application to different sensing scenarios can be envisaged.
The quantised nature of the electromagnetic field sets the classical limit to the sensitivity of position measurements. However, techniques based on the properties of quantum states can be exploited to accurately measure the relative displacement of a physical object beyond this classical limit. In this work, we use a simple scheme based on the split-detection of quantum correlations to measure the position of a shadow at the single-photon light level, with a precision that exceeds the shot-noise limit. This result is obtained by analysing the correlated signals of bi-photon pairs, created in parametric downconversion and detected by an electron multiplying CCD (EMCCD) camera employed as a split-detector. By comparing the measured statistics of spatially anticorrelated and uncorrelated photons we were able to observe a significant noise reduction corresponding to an improvement in position sensitivity of up to 17% (0.8dB). Our straightforward approach to sub-shot-noise position measurement is compatible with conventional shadow-sensing techniques based on the split-detection of light-fields, and yields an improvement that scales favourably with the detector's quantum efficiency.
Spatial quantum correlations in the transverse degree of freedom promise to enhance optical resolution, image detection, and quantum communications through parallel quantum information encoding. In particular, the ability to observe these spatial quantum correlations in a single shot will enable such enhancements in applications that require real-time imaging, such as particle tracking and in situ imaging of atomic systems. Here, we report on measurements in the far field that show spatial quantum correlations in single images of bright twin beams with 108{10}^{8}108 photons in a 1-$\ensuremath{\mu}\mathrm{s}$ pulse using an electron-multiplying charge-coupled-device camera. A four-wave mixing process in hot rubidium atoms is used to generate narrowband, bright pulsed twin beams of light. Owing to momentum conservation in this process, the twin beams are momentum correlated, which leads to spatial quantum correlations in the far field. We show around 2 dB of spatial quantum noise reduction with respect to the shot-noise limit. The spatial squeezing is present over a large range of total number of photons in the pulsed twin beams.