Entanglement in systems of oscillators and quantum computations
  It is shown that quantum devices based only on oscillators cannot serve as the universal quantum computer, despite of entanglement in such devices, which we roughly estimate for the ideal case and for the harmful entanglement with photonic modes. We show that quasi-particles are the native shell for the entanglement already for ground state, in contast to the free electromagnetic field where vacuum state does not produce entanglement at all. 
Yuri I. Ozhigov
physics.gen-ph quant-ph