Newly Tweaked Double Slit Experiment Designed for Time
Based on the original, scientists have found a way to apply the experiment to time rather than space
Hiya!
Ya know, I gotta applaud our ingenuity as a species. When we devote ourselves to a problem or mystery, there’s no stopping us — even if it takes decades or centuries to solve. And so rarely are we completely satisfied with the answer. One field that perfectly shows this is Science. No matter what we discover, we yearn to learn more, understand, and push beyond our limits and any obstacles in our path.
The double-slit experiment is a great example of this. It first appeared over a century ago and showed the world that light is made of both particles and waves. Since then, scientists have tweaked, expanded, and played with the experiment discovering enlightening (ha!) things along the way. But now, scientists have taken things to the next level by applying it to time rather than space.
Double Slit Experiment 1.0
Okay, so you’re probably already familiar with the original double-slit experiment, but we’re going to recap it anyway to help us better understand the most recent, upgraded version.
Thomas Young did the first double-split experiment performance in the early 1800s. He demonstrated that if a beam of light (composed of photons) is directed towards two narrow slits in a barrier, such as a card or a plate, the photons will interfere with each other as they pass through the slits. This causes a dark and light striped pattern on the observation screen behind the barrier.
But, when the light passes through only one slit, it spreads across the observation screen with a higher intensity in the center, then fades to the sides. Young’s experiment was some of the first evidence showing that light can be particles or waves depending on how it’s observed.
In the hundred-plus years since Young’s double-slit experiment, scientists have continued his methods and found it works for far more than just photons — Neutrons, electrons, and even entire atoms behave the same way. This simple experiment has established a fundamental principle of quantum physics as a theory that relies on probabilities.
And scientists aren’t finished finding ways to utilize the double-slit experiment. They’ve wondered for a while whether the experiment could produce the same results if it took place in time rather than space. And guess what? Physicist Riccardo Sapienza and his colleagues at the Imperial College London recently published a study in Nature Physics demonstrating that their long-held hunches are true.
Double Slit Experiment 2.0
Young’s original experiment was designed to study space, so Sapienza and his team needed to tweak the original method to one where the obstacles to the light’s propagation were separated in time instead. This was no easy feat, as Sapineza explains:
“The temporal manipulation of waves is an old subject, but it’s been mostly driven by theory for the last 30 years. It has been very hard to do experiments, especially with light.”
A significant challenge so far is finding materials that can switch from being reflective to translucent unfathomably fast in order to create what experts call “slits in time.” Amazingly, Sapienza and his time had the ingenious idea of using indium tin oxide (ITO), a material often used in coatings for many electronic displays. When shining a powerful laser beam at it, the material goes from being nearly transparent to briefly reflecting most of the light that hits it.
The Experiment
For Sapienza’s experiment, the ITO served as the barrier. While two consecutive laser pulses represented the slits by creating two distinct time stamps measuring when the laser hit the barrier and providing distinct paths in time where a single light wave can interfere with itself.
Then another, less powerful “probe” laser (to replace the observation screen) sent light through the material when it wasn’t reflective and bounced back when it collided with a laser pulse.
Lead author of the study, Romain Tirole, from Imperial College London, said:
“This is a very interesting experiment because it hasn't been done before, and we weren't sure whether it was possible. It was very exciting to be able to demonstrate that we can do this double-slit in time.”
The Result
The slight differences in time changed the light’s frequency when it struck the ITO, creating distinct colors rather than brightness levels. According to Sapienza, the light in Young’s experiment “enters [the slit(s)] at one angle and comes out at many angles, and in our experiment the light enters at one frequency and comes out at many frequencies.”
At least, that’s what their theoretical calculations predicted would happen, but what actually happened stunned everyone. See, the number of oscillations depends on how quickly the ITO transitions between transparent and reflective, but the transition far exceeded their expectations. Sapienza says:
“The material response is 10 to 100 times faster than expected, and that was a big surprise. We were hoping to see a few oscillations, and we saw many.”
The time slits were only a few femtoseconds apart. Yeah, I hadn’t heard of femtoseconds either, but the Massachusetts Institute of Technology (MIT) helps put it in perspective: “One femtosecond is to one second as one second is to about 32 million years.”
So, you know, really, really, crazy fast — also, can I just say how bonkers it is that we’re living during a time when scientists not only know what a femtosecond is but can measure them!
What It Means
Anyway, aside from how incredibly awesome it is that today’s scientists can conduct such a theory — and have it exceed expectations — there are other ways Sapienza’s experiment could advance physics.
For instance, the remarkable transition speeds could help scientists make and study time crystals — strange materials with moving structures that repeat indefinitely. In the future, experts hope to use time crystals as memory storage for quantum computers or to take highly precise time measurements to improve telecommunications that rely on them.
In a press release about their research, Sapienza says:
“Our experiment reveals more about the fundamental nature of light while serving as a stepping-stone to creating the ultimate materials that can minutely control light in both space and time.”
Tirole further explained the significance of their discovery:
“In our field of research, we've become really good at controlling the spatial aspect of light. In which direction does it propagate? How does it evolve in space? But time has always been a dimension that has not been accessible to us. But now that we have that extra dimension to manipulate, we can do very interesting things.”
Though the research could also be helpful in studying black holes. Really, the potential is endless because several new doors have been opened to the scientific community to further tweak and expand the double-slit experiment 2.0 as they did with the original. Who knows where it’ll end up.
Perspective Shift
I know none of this will impact our personal lives any time soon, but come on, it’s pretty cool our level of scientific study has reached such incredible heights. It increasingly feels like we’re living in a sci-fi novel. I know some people worry about such accelerations in technology and sciences — especially when, like now, it feels as though they are happening faster than we have time to think critically and ethically about them.
While I see and agree with some of the fears, there are positives to such rapid advancements beyond the promise they hold regarding helping people. Primarily that we’re in dire need of massive change. We’re going through some major transitions that will require stunning advancements. Still, this is why it’s good to become aware of progress as it happens, so we can discuss its implications before it impacts our personal lives.
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