he de Broglie–Bohm theory, also known as the pilot-wave theory, Bohmian mechanics, the Bohm or Bohm's interpretation, and the causal interpretation, is an interpretation of quantum theory. In addition to a wavefunction on the space of all possible configurations, it also postulates an actual configuration that exists even when unobserved. The evolution over time of the configuration (that is, of the positions of all particles or the configuration of all fields) is defined by the wave function via a guiding equation. The evolution of the wave function over time is given by Schrödinger's equation. The theory is named after Louis de Broglie (1892–1987) and David Bohm (1917–1992).
The de Broglie–Bohm theory is explicitly nonlocal: the velocity of any one particle depends on the value of the guiding equation, which depends on the configuration of the entire universe. Because the known laws of physics are all local, and because nonlocal interactions combined with relativity lead to causal paradoxes, many physicists find this unacceptable.