Surface Plasmons Enhanced Quantum Interference.

We report the effect of surface plasmons on the spatial correlations in frequency degenerate photons. It is found that the second-order degree of spatial coherence of the biphotons is manipulated due to the coupling of surface plasmons with the initial biphotons in a metallic subwavelength double-slit. Our results demonstrate that the second-order interference pattern in the resulting beam depends on slit parameters, coupling constant, and spatial coherence of the input beam. This suggests the possibility of amplifying spatial coherence in photonic qubits with an increase in coupling constant and a proper selection of slit separation. The comparison between surface plasmon-enhanced first-order and second-order interference patterns shows a significant increment in the amplitude of intensity for first-order as compared to the latter with an increase in coupling constant. We also illustrate the practical application of this research in material sensing. Furthermore, the study is anticipated to be beneficial in comprehending multi-particle quantum dynamics at the slit and finding applications in the regulation of spatial coherence in qubits for propagation through atmospheric turbulence, quantum sensing, and quantum imaging purposes. [ABSTRACT FROM AUTHOR]