Fig. 4: Results in entanglement-enabled quantum holography.

a Experimental setup. Light emitted by a laser diode at 405 nm and polarized at 45^∘ illuminates a stacked BBO crystal pair (0.5 mm thickness each) whose optical axes are perpendicular to each other to produce pairs of photons entangled in space and polarization by type-I SPDC. After the crystals, pump photons are filtered out by a band pass filter at 810 ± 5 nm. A lens f₁₁ is used to Fourier-image photon pairs onto an optical plane where an SLM with a phase object t₆. A two-lens imaging system f₁₂ − f₁₃ is then used to image the SLM and the object onto two different parts of an EMCCD camera. A polarizer (P) at 45^∘ is positioned before the camera. The biphoton correlation width in the camera plane is estimated as σ ≈ 9 μm. EMCCD camera pixel pitch is 16 μm. b Photo of the birefringent object used in the experiment (section of a bird feather). c Spatial phase of the object reconstructed by combining four anti-diagonal images Γ_{ij −i −j} measured for four phase shifts {0, π/2, π/2, 3π/4} programmed by the SLM. d Spatial phase of the same object reconstructed from four minus-coordinate projections P⁻. White scale bar is 1 mm.