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High-dimensional entangled states of light provide novel capabilities for quantum information, from fundamental tests of quantum mechanics to enhanced computation and communication protocols. In this context, the frequency degree of freedom is attracting a growing interest due to its robustness to propagation in optical fibers and its capability to convey large scale of quantum information into a single spatial mode. This provides a strong incentive for the development of efficient and scalable methods for the generation and manipulation of frequency-encoded quantum states. Nonlinear parametric processes are powerful tools to generate such states, but up to now the manipulation of the generated frequency states has been carried out mostly by post-manipulation, which demands complex and bulk-like experimental setups. Direct production of on-demand frequency-states at the generation stage, and preferably using a chip-based source, is crucial in view of practical and scalable applications for quantum information technologies.
Here we employ parametric down-conversion in an integrated AlGaAs chip to engineer the wavefunction and exchange statistics of frequency-entangled photon pairs directly at the generation stage, without post-manipulation [1]. Tuning the pump spatial intensity allows to produce frequency-anticorrelated, correlated and separable states, while tuning the spatial phase allows to tailor the symmetry of the spectral wavefunction. As revealed by Hong-Ou-Mandel interferometry, this allows to simulate either bosons, fermions, or anyons, i.e. particles displaying a fractional exchange statistics intermediate between bosons and fermions [2]. Finally, we show that the frequency entanglement can be combined with the polarization entanglement of our source to produce hybrid frequency-polarization entangled states [3], leading to quantum beating in two-photon interference. These results, obtained at room temperature and telecom wavelength, open promising perspectives for implementing quantum simulation tasks with tailored wavefunction and particle statistics in a chip-integrated platform.
[1] S. Francesconi et al, Optica 7, 316 (2020).
[2] S. Francesconi et al., ACS Photonics 8, 2764 (2021).
[3] S. Francesconi et al., in preparation.
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