  Structural physical approximation (SPA) has been exploited to approximate
non-physical operation such as partial transpose. It has already been studied
in the context of detection of entanglement and found that if the minimum
eigenvalue of SPA to partial transpose is less than $\frac{2}{9}$ then the
two-qubit state is entangled. We find application of SPA to partial transpose
in the estimation of optimal singlet fraction. We show that optimal singlet
fraction can be expressed in terms of minimum eigenvalue of SPA to partial
transpose. We also show that optimal singlet fraction can be realized using
Hong-Ou-Mandel interferometry with only two detectors. Further we have shown
that the generated hybrid entangled state between a qubit and a binary coherent
state can be used as a resource state in quantum teleportation.
