Abstract
Entanglement in high-dimensional quantum systems, where one or more degrees of freedom of light are involved, offers increased information capacities and enables new quantum protocols. Here, we demonstrate a functional source of high-dimensional, noise-resilient hyperentangled states encoded in time-frequency and vector-vortex structured modes, which in turn carry single-particle entanglement between polarisation and orbital angular momentum. Pairing nonlinearity-engineered parametric downconversion in an interferometric scheme with spin-to-orbital-angular-momentum conversion, we generate highly entangled photon pairs at telecom wavelength that we characterise via two-photon interference and quantum state tomography, achieving near-unity visibilities and fidelities. While hyperentanglement has been demonstrated before in photonic qubits, this is the first instance of such a rich entanglement structure involving spectrally and spatially structured light, where three different forms of entanglement coexist in the same biphoton state.
Highlights
Photonic platforms are a natural choice for many quantum applications owing to their advantages as low-noise quantum systems with high-fidelity control and suitability for long-distance transmission
We demonstrate a functional source of high-dimensional, noise-resilient hyperentangled states encoded in time-frequency and vector vortex structured modes, which in turn carry single-particle entanglement between polarization and orbital angular momentum
Pairing nonlinearity-engineered parametric downconversion in an interferometric scheme with spin-to-orbital-angular-momentum conversion, we generate highly entangled photon pairs at telecom wavelength that we characterize via two-photon interference and quantum state tomography, achieving near-unity visibilities and fidelities
Summary
Photonic platforms are a natural choice for many quantum applications owing to their advantages as low-noise quantum systems with high-fidelity control and suitability for long-distance transmission. We produce hyperentanglement between time-frequency modes (TFMs)— temporal/spectral envelopes of the electric field of the photons [6,21], and vector vortex beams (VVBs)—spatially structured beams characterized by a nonuniform polarization pattern on their transverse profile [23,24,25]. Due to their resilience to different noise sources, both TFMs [26,27] and VVBs [5,28] are ideal encodings for free-space communication schemes.
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