Quantum tunnelling is traditionally described within the confines of single-particle quantum mechanics, where it is assumed that the particle undergoing tunnelling is free of interactions with other particles. More precisely, the interactions with each individual particle are replaced by a simple external potential energy barrier (through which it may tunnel).

This framework is fundamentally incomplete because it does not account for many-particle effects, or include interactions mediated by "virtual" particles. Several approaches are studied to overcome these limitations, including imaginary-time mean-field techniques, S-matrix formalism, and quantum field theory.

Quantum field Theory (PHYS3201/6201)