Imagine a car passing through a locked gate without breaking it. It sounds like a scene from a sci-fi movie, but in the bizarre world of quantum physics, something just as bizarre happens for real.<\/p>\n
Particles like electrons can sometimes pass through energy barriers they wouldn\u2019t normally be able to cross, in a process known as quantum tunneling<\/a>. This mysterious behavior is the key to everything from nuclear fusion in stars to electronics in modern devices.\u00a0<\/p>\n Yet, scientists have long struggled to answer one fundamental question: How long does this tunneling take? This is because the timescales are unimaginably small, occurring within attoseconds<\/a> (billionths of a billionth of a second).\u00a0<\/p>\n However, a new study introduces a novel method that simplifies the measurement process and finally brings clarity to this long-standing tunneling mystery.<\/p>\n An improved attoclock technique<\/p>\n In 2008, a Swiss physicist named Ursula Keller invented special tools called attoclocks to try and catch the quantum tunneling process<\/a>. These clocks rely on a clever idea. If you hit an atom with a powerful laser, it can rip an electron away by pushing it through the quantum barrier.\u00a0<\/p>\n Since light has an electric field that rotates (imagine a spinning electric whip), the angle at which the electron comes out can give clues about when the tunneling happened. However, this method isn\u2019t perfect. The twisting laser field complicates things, and researchers need complex models to interpret the results. That often leads to unreliable conclusions.<\/p>\n \u201cAttoclock is a recently developed technique that offers an unprecedented time resolution (down to a few attoseconds, i.e., 10-18 sec). This technique is supposed to be perfectly suited for measuring the tunneling time. However, even after two decades of intensive work using attoclock, the question is still not answered,\u201d Wen Li, senior study author and a professor at Wayne State University, said<\/a>.<\/p>\n The study authors propose a new attoclock method. Instead of relying on older approaches that use swirling, elliptical beams of light, they designed a setup using perfectly circular light waves.\u00a0<\/p>\n More importantly, they focused on something known as the carrier-envelope phase (CEP), a tiny shift between the laser pulse and the peak of its electric field. Think of it like syncing the beat of a drum with the rise and fall of a wave.<\/p>\n When the atom is hit with this carefully timed laser pulse<\/a>, the electric field becomes strong enough to pull an electron out by tunneling. By capturing the moment when the field is at its peak, the researchers can pinpoint the exact instant the electron escapes.<\/p>\n \u201cCompared to conventional attoclock measurements, the phase-resolved attoclock truly tracks the peak of the electric field, which is the exact moment when electrons tunnel out. This suppresses any non-time-dependent factors that distort the results,\u201d Li said. Therefore, this new method is far more reliable than older techniques.\u00a0<\/p>\n What\u2019s the need to measure quantum tunneling?<\/p>\n When the team ran experiments to test their approach, they found that the electron doesn\u2019t seem to pause or get stuck during tunneling. In fact, the delay is so small it\u2019s almost nonexistent.\u00a0<\/p>\n Moreover, what truly determines how the electron escapes isn\u2019t the time it spends tunneling, but how strongly the atom was holding onto it in the first place. This challenges some traditional ideas in quantum physics and could reshape how we model ultrafast processes in atoms<\/a> and molecules \u2014 but this is not just it.<\/p>\n The study authors further suggest that their phase-resolved attoclock method is stable and precise enough to be adapted for real-time chemical analysis. Therefore, it could give scientists a way to observe reactions as they happen, something that could transform areas like drug development, nanotechnology<\/a>, and even quantum computing.\u00a0<\/p>\n \u201cBecause the technique is robust, we are currently working to develop it into a spectroscopic method so we can use it to study chemistry in real-time,\u201d Li added.<\/p>\n However, there are still tiny, almost imperceptible delays left to explore, and to catch those, the team plans to develop a next-generation tool\u2014a zeptoclock that can measure time down to zeptoseconds (a thousand times shorter than attoseconds).\u00a0<\/p>\n