Is this man in middle atack possible in quantum cryptography?
Is there something wrong it this scenario?


Obviously, yes.  Any such QKD system would require an authenticated channel back from Bob to Alice; that's to make sure that Bob is the one that's actually receiving the quantum signal, and not a man-in-the-middle.

More fundamentally, your system doesn't actually take advantage of any Quantum Effects; by measuring a particle, you can deduce its entire quantum state (or, at least, as much of the state that the protocol cares about); as such, it can be entirely described with classical physics.

There are actually several proposed QC systems; the simplest is probably the original BB84 system.  This system has the photon being in one of four quantum states, and takes advantage of the fact that a measurement will give only 1 bit (and this is the crucial quantum effect); using the authenticated channel, Alice and Bob can coordinate which of Bob's measurements gave answers consistent with what Alice sent; because the attacker cannot measure things without losing information, any attempt by him to measure and retransmit will introduce a measurable error rate.


  [Or] quantum cryptography is a big talk about nothing?


A number of people (including myself) are quite skeptical about quantum cryptography; however that doesn't have with us not thinking it doesn't work.  Instead, we look at the limitations (need for special quantum channel, cost of equipment, low data rate, low range, vulnerability to side channels), and ask "what advantage does it have compared with classical cryptography (either symmetric or asymmetric) to justify dealing with these limitations".