Negative Energy: From Lamb Shift to Entanglement
  "Negative energy" has been one of the most enduring puzzles in quantum theory, whereas the present work reveals that it actually plays a central role in clarifying various controversies of quantum theory. The basic idea is contained in a hypothesis on negative energy, and it is shown that the idea: (1)is compatible with both relativistic quantum mechanics and known experimental results; (2)helps to clarify the essence of matter waves, and therefore better understand the reality of the wave function, the so-called 'wave-packet reduction' occurring in quantum measurement, and the ghost like correlations between entangled systems; (3)is helpful for distinguishing the vacuum from the ground state of the quantized field, and may supply a possible way for removing the deep-rooted infinities in quantum field theory. The vacuum energy density of the electromagnetic field is calculated here as an example. By employing the same idea, the Lamb-Shift is recalculated in a different way from conventional renormalization method, yet the same result as Bethe's can be definitely obtained. 
Shou-Liang Bu
physics.gen-ph