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
P-adic quantum mechanics wave functions, in which case the problem of the probabilistic interpretation of the "p"-adic valued wave function arises. As there does not exist a suitable "p"-adic Schrödinger equation, path integrals are employed instead. Some one-dimensional systems have been studied by means of the path integral formulation, including the free particle, the particle in a constant field, and the harmonic oscillator. P-adic quantum mechanics p"-adic quantum mechanics is a collection of related research efforts in quantum physics that replace real numbers with "p"-adic numbers. Historically, this research was inspired by the discovery that the Veneziano amplitude of the open bosonic string,