Two-photon interference between two well-separated pulses

Summary form only given. The superposition principle is at the heart of quantum mechanics and plays the central role in interference phenomena in quantum mechanics. Quantum interference differs from classical interference because of particle nature of light. In a quantum mechanical picture, interference occurs because there are indistinguishable ways of an event to occur. Whenever which-path information is given to the system, interference disappears. We have experimentally demonstrated that two-photon interference occurs for biphoton amplitudes arising from two well-separated pump pulses.