Abstract
In this work, we experimentally demonstrate a photon-pair source with correlations in the frequency and polarization degrees of freedom. We base our source on the spontaneous four-wave mixing (SFWM) process in a photonic crystal fiber. We show theoretically that the two-photon state is the coherent superposition of up to six distinct SFWM processes, each corresponding to a distinct combination of polarizations for the four waves involved and giving rise to an energy-conserving pair of peaks. Our experimental measurements, both in terms of single and coincidence counts, confirm the presence of these pairs of peaks, while we also present related numerical simulations with excellent experiment-theory agreement. We explicitly show how the pump frequency and polarization may be used to effectively control the signal-idler photon-pair properties, defining which of the six processes can participate in the overall two-photon state and at which optical frequencies. We analyze the signal-idler correlations in frequency and polarization, and in terms of fiber characterization, we input the SFWM-peak experimental data into a genetic algorithm which successfully predicts the values of the parameters that characterize the fiber cross section, as well as predict the particular SFWM process associated with a given pair of peaks. We believe our work will help advance the exploitation of photon-pair correlations in the frequency and polarization degrees of freedom.
Highlights
In this work, we experimentally demonstrate a photon-pair source with correlations in the frequency and polarization degrees of freedom
From the frequency-resolved photon counting measurements, we find that for a wide interval of pump wavelengths, accessible from our Ti:sapphire laser, the PCF used as source fulfills phase-matching for all six spontaneous four-wave mixing (SFWM) processes comprising the two-photon quantum state given by Eq (4)
We have demonstrated a photon-pair source, exhibiting correlations in the polarization and spectral degrees of freedom, based on the spontaneous four-wave mixing (SFWM) process in a polarization-maintaining photonic crystal fiber
Summary
We experimentally demonstrate a photon-pair source with correlations in the frequency and polarization degrees of freedom. Photon pair generation based on the χ (3) nonlinearity holds much promise for the advancement of quantum processing technologies[1] These sources rely on the spontaneous four-wave mixing (SFWM) p rocess[2], in which two pump photons are annihilated, leading to the emission of signal and idler photon pairs. Among the above optical fiber alternatives, it is well known that PCFs exhibit unique characteristics that make them an attractive medium for photon-pair source implementations[13,22,23], exhibiting engineered dispersion properties leading to spectrally or temporally tailored two-photon state generation, and high effective nonlinear coefficients permitting large emission rates. Photon pairs with hybrid entanglement have been proposed or demonstrated in the following degrees of freedom: path-polarization[34], frequency-spatial fiber m ode[35], polarizationtransverse spatial[36,37], and polarization-orbital angular momentum[38,39,40]
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