Suppose a Fock state contains 2 photons, both in the same spacetime mode and having the save (vertical) polarization. So we can write this state as |2>, or, if we want to emphacize its vertical polarization, we may write |2v> or |2v,0h>. Suppose now we want to measure polarization in the circular (R,L) basis.(adsbygoogle = window.adsbygoogle || []).push({});

If we had only a single photon, the question would be trivial. It would end up R or L polarized with the same probability 1/2.

What happens when there are 2 photons? If each photon again makes an independent decision, then we will have 1/4 chance to find both photons R-polarized, 1/4 chance to find them both L-polarized, and a 1/2 chance to find them in different polarization states. In other words, we will get the analogue of Malus's law for the 2-photon case.

Is this picture correct? And if yes, then how come the Fock state |2v> is NOT identical to the product state |1v>|1v>, when it behaves exactly the same way?

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Probability amplitudes and photons

**Physics Forums | Science Articles, Homework Help, Discussion**