The question of how long a particle takes to tunnel through a potential barrier has sparked a long-standing debate since the early days of quantum mechanics. To solve this problem, scientists in China have proposed and demonstrated a novel attosecond-scale streaking method to accurately determine the tunneling time of an electron from an atom. The experimental results have shown that the tunneling time is close to zero with a precision of a few attoseconds.
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Source: Phys.org