Photon statistics of intense entangled photon pulses

Abstract

Time-and frequency-gated two-photon counting is given by a four-time correlation function of the electric field. This reduces to two times with purely time gating. We calculate this function for entangled photon pulses generated by parametric down-conversion. At low intensity, the pulses consist of well-separated photon pairs, and crossover to squeezed light as the intensity is increased. This is illustrated by the two-photon absorption signal of a three-level model, which scales linearly for a weak pump intensity where both photons come from the same pair, and gradually becomes nonlinear as the intensity is increased. We find that the strong frequency correlations of entangled photon pairs persist even for higher photon numbers. This could help facilitate the application of these pulses to nonlinear spectroscopy, where these correlations can be used to manipulate congested signals.

Matter correlations induced by coupling to quantum light

“…When the pump intensity is increased, photon pairs from different Gaussian stochastic light, E † E E † E . As shown in [51], the first line dominates for low pump intensities, and with increasing intensity we can observe a crossover between the two contributions. Figure 7 shows the density matrices for different pump intensities.…”

Two-photon spectroscopy of excitons with entangled photons

“…16 However, as pointed out in Ref. 32, this crossover which occurs for α 0.002 in Figure 5 does not coincide with the crossover in the behavior of the four-point correlation function which occurs when the red and blue lines are of similar strength at α 0.01. This can clearly be seen in Figure 4, where panels (a) and (b) look virtually identical, even though only panel (a) can be described by the twin state.…”

“…The set of control parameters includes the pump pulse frequency ω p and its bandwidth σ p , the central frequencies of the downconverted beams ω 1 and ω 2 , their entanglement time T specifying their bandwidths, and the amplitude of the pump pulse α as discussed in Ref. 32. δt is a variable delay.…”

“…From the analysis of the field correlation function, 32 we know that the coherent contribution of pairs of entangled photons scales as sinh (r k ) cosh (r k ), and the incoherent autocorrelation contribution of uncorrelated photons as sinh 2 (r k ). At low pump intensities, r k 1, we can neglect the latter contribution, and approximate the former as sinh (r k ) cosh (r k ) ≈ r k .…”

Virtual-state spectroscopy with frequency-tailored intense entangled beams

“…To describe the generation of twin beams, we follow the procedure used by previous authors in Refs. [38,39,[42][43][44][45][46]. The first step is to solve the Schrödinger equation in the first-order perturbation approximation to obtain the two-photon spectral amplitude.…”