What is Quantum Tunneling?

Henry and Eve have been locked behind bars by their captors. Eve recalls that Henry accidentally stepped into the focal area of multiple laser beams and found himself in her office, having gone through the wall! This effect is called “quantum tunneling”. Eve’s reminiscence makes Henry realize that enhanced tunneling through the jail bars is achievable by a periodic force at the tunneling resonance frequency. Tunneling underlies diverse processes: nuclear radioactive decay, transistor action, superconducting junction operation and ultracold gas dynamics. It may be explained as predominantly destructive interference between quantum wavepacket portions inside the barrier, and can be drastically enhanced or suppressed via interplay between environment and control effects. Tunneling exemplifies the shattering of spacetime concepts that may profoundly affect human existence. The appendix to this chapter discusses Schrödinger’s wavefunctions in tunneling.