Nonexponential Tunneling due to Mean-Field-Induced Swallowtails.

Area of Science:

• Quantum mechanics
• Atomic physics
• Condensed matter physics

Background:

• Energy levels typically change smoothly with control parameters.
• Bifurcations in energy spectra can lead to complex structures like loops and swallowtails.
• Nonlinear Hamiltonians are key to exploring exotic quantum behaviors.

Purpose of the Study:

• To experimentally implement and observe quantum swallowtails.
• To validate ultracold atoms in optical lattices as a platform for studying quantum phenomena.
• To investigate self-trapping and nonexponential tunneling.

Main Methods:

• Implementation of a nonlinear 2x2 quantum Hamiltonian using ultracold atoms.
• Utilizing a moving one-dimensional optical lattice.
• Observing self-trapping and tunneling probabilities.

Main Results:

• Experimental observation of self-trapping phenomena.
• Measurement of nonexponential tunneling probabilities, a signature of swallowtails.
• Good agreement between experimental results and theoretical predictions.

Conclusions:

• The optical lattice system effectively implements quantum Hamiltonians supporting swallowtails.
• This system is a powerful platform for studying Josephson junction physics.
• The system enables research into superfluidity in ring-shaped geometries.