Quantum motion occurs in configuration-space particle trajectories associated with the de Broglie–Bohm causal interpretation of quantum mechanics. Previous Demonstrations (see Related Links) showed that the motion of a quantum particle could be obtained when the corresponding particle density (given by the modulus of the Schrödinger wavefunction) is not time dependent.

This Demonstration considers a three-dimensional anharmonic oscillator described by a trigonometric Pöschl–Teller potential in a degenerate stationary state with a constant phase shift. Two particles are placed on the margin of the potential randomly and separated by an initial distance .

A system with three degrees of freedom assigned by a superposition of three coherent stationary eigenfunctions that has commensurate energy eigenvalues and with a relative constant phase shift can exhibit chaotic motion in the associated de Broglie–Bohm picture, provided that the constant phase is not zero or an integer multiple of (see Bohm Trajectories for a Particle in an Infinite 3D Box). The origin of the motion lies in the relative phase of the total wavefunction, which has no analog in classical particle mechanics. The dynamical structure is quite complex. Some of the curves are closed and periodic, while others are quasiperiodic. In the region of nodal points of the wavefunction, the trajectories apparently become accelerated and chaotic. The parameters have to be chosen carefully, because of the singularities of the velocities and the large oscillations that can lead to very unstable trajectories. Further investigation to capture the full dynamics of the system is necessary.

The graphics show three-dimensional contour plots of the squared wavefunction (if enabled) and two initially neighboring trajectories. To modify the constant phase shift , change para in the initialization code and restart. Black points mark the initial positions of the two quantum particles and green points mark the actual positions. Blue points indicate the nodal point structure.