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 (franchise) although in certain titles elements such as falls cannot do this, and instead just leave the fighter with very low health. Since "Dead or Alive 2", the series has implemented its tag team fighting system, allowing characters to switch back and forth for combo attacks and even attack simultaneously when timed correctly. The tag mode also included special throws unique to certain pairs of characters and allows for the participation of four players, something not common in the genre. "Dead or Alive 3" introduced Attack Change, a new tag system feature where the fighting character can switch places with a