Absolute calibration of a charge-coupled device camera with twin beams

Abstract

We report on the absolute calibration of a CCD camera by exploiting quantum correlation. This novel method exploits a certain number of spatial pairwise quantum correlated modes produced by spontaneous parametric-down-conversion. We develop a measurement model accounting for all the uncertainty contributions, and we reach the relative uncertainty of 0.3% in low photon flux regime. This represents a significant step forward for the characterizaion of (scientific) CCDs used in mesoscopic light regime. PACS numbers: Valid PACS appear hereIntroduction. The development of quantum metrology, imaging and sensing [1-6] based on quantum optical states aim to reach sensitivity beyond classical limits. For this reason it requires new detection strategies in the low light intensity regime (down to few photons), that are far from the ones where traditional radiometry operates [7]. Development of dedicated methods for absolute calibration of detectors in this context is therefore necessary, as it is widely recognised inside the radiometric community [8]. Some specific activities in this context are already on-going [9, 10], in particular related to the calibration of single-photon detectors exploiting the Klyshko's twinphoton technique [11][12][13][14][15][16][17][18] and its developments [19][20][21][22][23][24][25].In particular, demand for precise calibration of detectors both in mesoscopic light regime it is relevant not only from the point of view of the development of quantum technologies, but also for establishing a connection between the light intensity level typical of classical radiometric measurements and the quantum radiometry operating at single-photon level [8, 9]. Quantum correlations in twin beams offer an opportunity for reaching this goal, as discussed in [26][27][28][29].In [30] we realized the first absolute calibration of a standard CCD camera by exploiting bright squeezed vacuum. Standard CCD cameras, i.e. without any avalanche electro-multiplication, are able to count the number of generated photo-electron in each pixels for a given exposure time with a read-out noise ∆ RN of few photoelectron (for top-level devices), independent of the exposure time. However, a single photon can not be distinguished from the noise and the time resolution does not allow time tagging and coincidence of photon arrivals, instead the signal is proportional to the intensity (analog regime). If a light signal generate N photo-electron, under the condition ∆ RN << N 1/2 , sub-shot-noise sensitivity can be achieved [31][32][33], a properties that has been used also for quantum enhanced sensing and imaging protocols [2,33].The method in [30] is based on the sub-shot-noise measurement of photon number correlation between a pair

Absolute calibration of an EMCCD camera by quantum correlation, linking photon counting to the analog regime

“…In particular, we measure the noise reduction factor ζ = [δ(N 1 − αN 2 )] 2 / N 1 − αN 2 ) and the correlation C = N 1 N 2 − N 1 N 2 ; where α = N 1 / N 2 , N 1 and N 2 being the number of photons in the two correlated areas. These quantities are related to the mean detection efficiency η by: ζ ≃ 1+α 2 − ηA and C ≃ ηA N 1 both in analog and photon counting regime for low photon number per mode; where A is a geometrical parameter [41].…”

Quantum differential ghost microscopy

“…In all the cases considered, see fit the experimental data properly, falling almost all the data in the 1σ confidence region. A further element of consistency of the model is the accordance between the value of η obtained from the fit and the one independently estimated with the absolute technique described in [43][44][45][46], which extends the Klyshko method [47,48]. Indeed, referring for example to Fig.…”

Unbiased estimation of an optical loss at the ultimate quantum limit with twin-beams

“…On the other side S ′ α , in particular to calculate k and δE, requires the knowledge of the two absolute values of both the efficiencies η R and η P , virtually without uncertainty. Even if, in principle, they can be determined from the same set-up by using some extensions of the Klyshko's method [53][54][55] (i.e. as described in the previous section they can be extracted from the measured value of σ γ ) this could become cumbersome and it affects the final accuracy; in particular it requires firstly a long enough time to reduce the uncertainty to a negligible level and secondly a stability of the system from the characterization stage to the true measurement stage.…”

“…In our case, integrating on the two regions of interest this condition is fully fulfilled, indeed it holds A det ≫ A coh . In general the measured NRF can be modelled as [53]: σ γ = 1+γ 2 − η R η coll ≥ 0, where two contributions are present.…”