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 Sega Saturn version, and is generally considered more of a collector's disc than for its content. "Dead or Alive Ultimate 2", being a remake created after the debut of "Dead or Alive 3", takes elements and mechanics from both its original iteration and successor. The action of 3D-axis movement is as free-formatted as "DOA3", and Hitomi is now a playable character albeit outside story mode. Other elements have been kept intact from "DOA2". These include higher damaging counters than in "DOA3", environmental hazards not warranting a knockout on a character, and a counter mechanism that is much harder to execute.