Flat-optics generation of broadband photon pairs with tunable polarization entanglement

Abstract

The concept of `flat optics' is quickly conquering different fields of photonics, but its implementation in quantum optics is still at infancy. In particular, polarization entanglement, which is central to quantum photonics due to the simplicity of polarization qubit encoding and control, is so far not realized on flat platforms. Meanwhile, relaxed phase matching of flat nonlinear optical sources enables enormous freedom in tailoring their polarization properties. Here we use this freedom to generate photon pairs with tunable polarization entanglement via spontaneous parametric down-conversion (SPDC) in a $400$ nm GaP film. By changing the pump polarization, we tune the polarization state of photon pairs from maximally entangled to almost disentangled, which is impossible in a single bulk source of SPDC. Polarization entanglement, in combination with the broadband frequency spectrum, results in an ultranarrow (12 fs) Hong-Ou-Mandel effect and promises extensions to hyperentanglement.

References in corpus (18)

• Entanglement of Formation of an Arbitrary State of Two Qubits
• Quantum computational advantage using photons
• Secure quantum key distribution with realistic devices
• Significant-loophole-free test of Bell's theorem with entangled photons
• Non-maximally entangled states: production, characterization and utilization
• Metasurfaces for Quantum Photonics
• Quantum metasurface for multi-photon interference and state reconstruction
• SuperDense Teleportation using Hyperentangled Photons
• Microscale generation of entangled photons without momentum conservation
• Polarization state of a biphoton: quantum ternary logic
• Nonmaximally entangled states can be better for multiple linear optical teleportation
• Efficient quantum key distribution scheme with nonmaximally entangled states
• Theory of cavity-enhanced spontaneous parametric downconversion
• Demonstration of second harmonic generationin gallium phosphide nano-waveguides
• Idealised EPR states from non-phase matched parametric down conversion
• Complex-birefringent dielectric metasurfaces for arbitrary polarization-pair transformations
• Polarization-sensitive quantum-optical coherence tomography
• Measurement of qutrits