There is no interference pattern from a single photon as it hits the registration device at a particular place. But collect a big enough sequence of single photon measurements and it emerges.
This is the reason for statistical interpretation of QM that states that a wave function is just a way to calculate probability with no inherent meaning.
So wave-particle duality is just an artifact of Copenhagen interpretation of QM, not something that one can observe. What one clearly observes that photons travel through a region where they should not classically be and never appear in the region where they should be classically.
Note that even classically waves does not exist as they are just an artifact of motion of collection of molecules that on average can be described by wave-like equations.
This is the reason for statistical interpretation of QM that states that a wave function is just a way to calculate probability with no inherent meaning.
So wave-particle duality is just an artifact of Copenhagen interpretation of QM, not something that one can observe. What one clearly observes that photons travel through a region where they should not classically be and never appear in the region where they should be classically.
Note that even classically waves does not exist as they are just an artifact of motion of collection of molecules that on average can be described by wave-like equations.