Quantum tunneling mystery solved after 100 years—and it involves a surprise collision

Physicists have solved a century-old mystery about quantum tunneling, discovering that electrons collide with atomic nuclei inside energy barriers. This "under-the-barrier recollision" process, observed using intense laser pulses, challenges previous assumptions and reveals unexpected electron behavior during tunneling. The findings could advance technologies like semiconductors and quantum computing by enabling more precise control of electron dynamics.