Wigner's friend and continuous time evolution of the state of a closed system and the probabilistic, discontinuous collapse of the state of a system upon measurement. Wigner's friend is therefore directly linked to the measurement problem in quantum mechanics with its famous Schrödinger's cat paradox. The thought experiment posits a friend of Wigner in a laboratory and lets him perform a quantum measurement on a physical system (this could be a spin system or also Schrödinger's cat). This system is assumed to be in a superposition of two distinct states, say, state 0 and state 1 (or "dead" and "alive", in the
Dead or Alive Ultimate 2", some changes to the music and remixes were added. Each character except Hitomi (which was introduced in "DOA3") has their own remix. The remixes only appear in the Dance Floor stage, The Ray House. The story mode of "Dead or Alive Ultimate" plays out as it did in the original. However, a new CG sequence is added further explaining the relationship and history of Ayane, Kasumi and Hayate leading into the first two Dead or Alive games. In 2004, after the release of "Dead or Alive 3", Team Ninja once again remade "Dead or Alive 2", this time for