Description
Hyperentanglement allows simultaneous quantum entanglement across multiple degrees of freedom (DOFs), scaling quantum technologies. Miniaturised devices offer higher biphoton pair-generation rates than bulk optics [1], while waveguide confinement minimises environmental decoherence [2]. However, shifting between distinct hyperentangled Bell states typically requires hardware modifications or lossy post-selection. Furthermore, conventional frameworks rely on a static tensor product, failing to capture simultaneous polarisation-spatial relationships during propagation. To resolve this, we bypass the tensor product entirely and formulate a continuous system of sixteen coupled differential equations tracking the evolution of all polarisation-spatial combinations. Extending biphoton wavefunction dynamics [3], this model integrates signal and idler modes within a two-channel nonlinear coupled waveguide system. This approach enables deterministic switching between different on-chip hyperentangled states solely by reconfiguring eight complex input pump amplitudes, removing structural modifications or post-processing. Our numerical analysis identifies optimal conditions for hyperentanglement generation by evaluating phase mismatch, coupling coefficients, propagation distance and effective nonlinearity. The resulting 4x4 biphoton correlation matrices demonstrate high-contrast Bell state generation with zero leakage. Each target state exhibits perfectly balanced peak amplitudes, distributing probability equally at 0.25 to confirm true, maximally hyperentangled Bell states. By varying only the eight complex pump amplitudes, we demonstrate that our simple two nonlinear waveguide channel system allows for flexible hyperentanglement state switching. The distinctiveness of these correlations ensures pure state identification, validating this architecture for quantum applications. Future work will extend this to specific waveguide geometries and metasurfaces [1,4].
References
1. Solntsev AS, et al. Nat Phot. Nat Res. 2021 15(5):327-336.
2. Huang Y, et al. Phys Rev Appl. 2022 17(5):054002.
3. Wu CW, et al. Opt Lett. 2014 39(4):953.
4. Sharapova PR, et al. Laser Photon Rev. John Wiley and Sons Inc. 2023 17(4):2200408.
| I am the presenting author | Yes |
|---|