eng Science and Education Publishing International Journal of Physics 2333-4576 2025-08-03 13 3 73 79 10.12691/ijp-13-3-5 IJP20251335 article Simanshu Kumar 1 Nandan S Bisht bisht.nandan@gmail.com 2 Department of Physics, Kumaun University Nainital, S.S.J. Campus, Almora, 263601, Uttarakhand, India Department of Physics, Soban Singh Jeena University, S.S.J. Campus, Almora, 263601, Uttarakhand, India This study lights on the phenomenon of quantum decoherence when Biphoton and Schrödinger cat states are evolve. The primary focus of the work is to explore and analyze the phenomenon of decoherence by virtue of the insightful representations on the way of deriving the Wigner function for the considered states. A crucial aspect of this work involves shedding light on the behaviour of Biphoton and Schrödinger cat states with the same spatial modes and similar theoretical tomography. By considering the influence of an external environment, we further extend our exploration of decoherence, aiming to understand how environment as a factor, impact the stability and coherence of these quantum states. https://pubs.sciepub.com/ijp/13/3/5/ijp-13-3-5.pdf Hong-Ou-Mandel interferometer Wigner function Decoherence Entanglement