Fig. 4. Creation of classical GHZ states.

The experimental setup used to generate the classical GHZ states from our laser, including the core steps of high-dimensional state generation (laser), GHZ-state generation and two measurement steps to confirm the state properties. a Shows the required path and polarisation transformations needed for each GHZ state, performed by the iris (located at I₁ or I₂) and SLM phase masks (3π/2 and π/2), respectively. In b and c, this is unpacked graphically for the SLM modulation, altered in the polarisation of each ray state, and the iris modulation, where the incoming four lobes are reduced to two. d Shows the results for the vector beam corresponding to the first maximally entangled group $∣{\mathrm{\Phi }}^{\pm }⟩$, obtained both experimentally (Exp.) and simulated (Sim.). The arrows depict the orientation of the polarizer in the measurement stage of the OAM-state measure. In the tomography measurement (Bell-state measure), each of the eight GHZ states can be inferred by just a polarizer and a CCD camera. The CCD camera is moved to different locations and captures the interferometric fringes for a visibility calculation. e The final trajectory in space of one of the GHZ states, showing the two-lobed structure. (OC output coupler mirror, DM dichroic mirror, PBS polarisation splitting prism, QWP quarter-wave plate, HR high-reflective mirror, PR partial-reflective mirror, SLM spatial light modulator, CCD charge-coupled device camera, P polarizer)