At a Glance
- Scientists designed an experiment to test a prediction of Bohmian mechanics, an alternative interpretation of quantum theory that describes how subatomic particles behave when tunneling through barriers.
- The Bohmian view uniquely predicts that a particle would remain stationary, taking an infinite amount of time to cross an infinitely long barrier, a concept the researchers tested.
- Using a system of two coupled waveguides, the team created a quantum clock to measure the speed of photons as they tunneled through a simulated infinite potential barrier.
- The experiment revealed that the tunneling time was finite, directly contradicting the Bohmian prediction and showing that particles with more negative local kinetic energy traveled even faster.
- These findings, published in Nature, contribute significant new evidence to the ongoing debate about tunneling time and the fundamental accuracy of different interpretations of quantum mechanics.
In a fascinating peek into the bizarre nature of reality, scientists have conducted an experiment to test a controversial interpretation of quantum mechanics, the theory governing the subatomic world. At the heart of the study is a phenomenon known as quantum tunneling, where particles, such as photons, can pass through barriers that should be impenetrable according to classical physics. Researchers aimed to measure how long this seemingly impossible journey takes, a question that has puzzled physicists for decades and pits two major quantum theories against each other.
Quantum mechanics has long been split between two main interpretations. The standard “Copenhagen” view suggests that until measured, a particle exists as a wave of probabilities without a definite location. In contrast, an alternative theory known as Bohmian mechanics proposes that particles are always in a specific location, guided by an invisible “pilot wave.” This alternative makes a strange prediction: a particle tunneling through an infinitely long barrier should become stationary, spending an infinite amount of time inside it.
Reporting in the journal Nature, a research team designed an ingenious experiment to test this very prediction. They created a setup using two parallel, light-guiding channels called waveguides. As photons—particles of light—traveled down one waveguide and tunneled into a simulated infinite barrier, they also jumped back and forth into the second waveguide. This jumping occurred at a predictable rate, effectively acting as a clock that allowed the scientists to calculate the photons’ speed and how long they “dwelled” inside the barrier.
The results challenge the prediction made by Bohmian mechanics. The experiment measured a finite, not infinite, time for the photons to tunnel through the barrier. Furthermore, the researchers found that particles with more negative local kinetic energy—a strange quantum effect that can occur inside a barrier—traveled faster. The team writes to Phys.org, “we find that the measured energy–speed relationship does not align with the particle dynamics postulated by the guiding equation in Bohmian mechanics.” While the findings do not definitively rule out the Bohmian view, they add crucial new data to a long-standing debate about the fundamental nature of our universe.
References
- Blue, C. & Phys.org. (2025, July 10). Speed test of ‘tunneling’ electrons challenges alternative interpretation of quantum mechanics. Phys.Org; Phys.org. https://phys.org/news/2025-07-tunneling-electrons-alternative-quantum-mechanics.html
- Fedrizzi, A., & Biancalana, F. (2025). Tunnelling photons challenge interpretation of quantum mechanics. Nature, 643(8070), 37–38. https://doi.org/10.1038/d41586-025-01765-x
- Sharoglazova, V., Puplauskis, M., Mattschas, C., Toebes, C., & Klaers, J. (2025). Energy–speed relationship of quantum particles challenges Bohmian mechanics. Nature, 643(8070), 67–72. https://doi.org/10.1038/s41586-025-09099-4
