WAVEFRONT CONTROL FOCUS the emulation of two-photon coherent absorption experiments [ 6 ] and the implementation of arbitrary high-dimensional quantum gates for spatially entangled two-photon states [ 11 ]( Fig. 2( a)).
Researchers have also developed approaches in which disorder is treated as an obstacle to be overcome. For instance, by shaping the
Figure 3. From shaping non-classical light to non-classical light shaping. Optimization algorithms driven by quantum feedback( e. g. spatial mode coincidence rates) can identify SLM phase patterns that refocus photon coincidences through a scattering medium. Consequently, the medium becomes effectively transparent for the entangled state while remaining opaque to classical light.( a) Coincidence rate optimization curve of spatially-entangled photon pairs propagating through a thin scattering layer.( b) Two-photon speckle measured before optimization.( c) Optimal phase pattern obtained at the end of the process.( d) Refocused twophoton speckle using the optimal phase.( e) In contrast, propagating classical coherent light with this exact phase pattern yields a complex speckle pattern, demonstrating no refocusing. More details in Ref.[ 15 ].
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