  We propose the concept of one-sided quantum interference based on
non-Hermitian metasurfaces.By designing bianisotropic metasurfaces with a
non-Hermitian exceptional point, we show that quantum interference can exist
only on only one side but not another. This is the quantum inheritance of
unidirectional zero reflection in classical optics.The one-side interference
can be further manipulated with tailor-made metasurface. With two photons
simultaneously entering the metasurface from different sides, the probability
for only outputting one photon on the side with reflection can be modified to
zero as a one-sided destructive quantum interference while the output on
another side is free of interference. We design the required bianisotropic
metasurface and numerically demonstrate the proposed effect. The non-Hermitian
bianisotropic metasurfaces provide more degrees of freedom in tuning two-photon
quantum interference, in parallel to the celebrated Hong-Ou-Mandel effect.
