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Area of Science:

  • Quantum mechanics
  • Atomic physics
  • Condensed matter physics

Background:

  • The time a quantum particle spends within a potential barrier during tunneling is a fundamental, yet experimentally challenging, question.
  • The Larmor clock is a theoretical proposal to measure this dwell time by utilizing an auxiliary particle degree of freedom.

Purpose of the Study:

  • To experimentally measure the dwell time of ultracold atoms tunneling through an optical barrier.
  • To verify theoretical predictions regarding tunneling times and their dependence on barrier height and particle energy.

Main Methods:

  • Precise Larmor time measurements were performed using ultracold Rubidium-87 (⁸⁷Rb) atoms.
  • Atoms were directed through a tunable optical potential barrier, and their interaction time within the barrier was clocked.

Main Results:

  • The experimental results confirm longstanding theoretical predictions for quantum tunneling times.
  • Dwell time within the barrier decreases for higher barriers and lower incident particle energies.
  • At the lowest measured energy, 90% of transmitted atoms spent an average of 0.59±0.02 ms in the barrier.

Conclusions:

  • The Larmor clock is a viable method for measuring quantum tunneling dwell times.
  • Experimental validation of tunneling time predictions provides deeper insight into quantum transport phenomena.