Scientists have discovered “unexpected physics” by opening up “slits” in time, a new study reports, achieving a longstanding dream that can help to probe the behavior of light and pioneer advanced optical technologies.
The mind-boggling approach is a time-based variation on the famous double-slit experiment, first performed by Thomas Young in 1801, which opened a window into the weird probabilistic world of quantum mechanics by revealing the dual nature of light as both a particle and a wave.
The new temporal version offered a glimpse into the mysterious physics occurring at extremely fast timescales. This may help to develop quantum computing systems and other future-generation applications.
In the original double-slit experiment light travels through two separate slits on an opaque screen. A detector on the other side of the screen records the pattern of the light waves that emerges from the slits. The experiments showed that the light waves changing direction after passing through the slits caused them to interact with one another. This shows that light can behave as both a particle and a wave. This insight was a major milestone in our continuing journey to the quantum world. It has been replicated with electrons and other entities since, which exposed the bizarre phenomena occurring at small scales within atoms.
Now, scientists led by Romain Tirole, a PhD student studying nanophotonics at Imperial College London, have created a “temporal analogue of Young’s slit experiment” by firing a beam of light at a special metamaterial called Indium Tin Oxide, according to a study published on Monday in Nature Physics.
Metamaterials are artificial creations endowed with superpowers that are not found in nature. The new study shows that Indium Tin Oxide can alter its properties within a matter of milliseconds. This is a fraction of one millionth of billionths of a second. The incredible variability of light waves allows them to interact with metamaterials at crucial moments in very fast succession. These are called “time slots”, which produce a time-based pattern for diffraction that’s similar to those found in the spatial experiment.
“Showing diffraction from a double slit in time requires to flick a switch extremely fast, on time scales comparable to how fast the light field oscillates, about a few femtoseconds,” said Tirole in an email to Motherboard. “If the entire history of the universe from the Big Bang to the moment you read this was a second, an oscillation of light would only take the equivalent of a single day!”
“Switching at this speed has long been difficult, but a few years ago a new material, Indium Tin Oxide, which already covers the screens of our mobile phones or televisions, was shown to switch very fast when you shine an intense laser beam on it,” he continued. “This has enabled a rapid progress of the field–see for example a conference we are organizing.”
In other words, the super-speedy changeability of Indium Tin Oxide finally made a time slit experiment possible, after many years of eluding scientists. To bring this vision to reality, Tirole and his colleagues used lasers to switch the reflectance of the material on and off at high speeds.
When the material was turned on, it essentially became a mirror that allowed the team to record the diffraction patterns of light beams that interacted with the highly reflective surface. These were called time slits and they form the foundation of the experiment. Researchers observed oscillations in the patterns that resulted from the separation of these slits.
To the team’s astonishment, the results of the experiment revealed more oscillations than predicted by existing theories, as well as far sharper observations, which points to “unexpected physics” in the findings, according to the study.
“When we measured the spectra, we were very surprised by how clear they showed up on the detectors,” Tirole said. “How visible these oscillations are depends on how fast we can switch our metasurface on and off [and] this means that the speed at which our metamaterial changes is much faster than what was previously thought and accepted. This is exciting as it implies that new physical mechanisms are still to be uncovered and exploited.”
“In our experiment we show that this wonder material has an even faster switching speed, 10-100 times faster than previously thought, which enables a much stronger control of light,” he also noted. This temporal experiment with the double-slit experiment changed the frequency and color of light. The result was distinctive, where some colors were amplified while others were cancelled out. These results were similar to those created by the spatial version. Light waves are produced that nullify and bolster each other once they pass through the slits.
The breakthrough paves the way toward new research into the enigmatic properties of light, and the many emerging technologies that rely on optical phenomena. Tirole and his colleagues are especially eager to try to repeat the experiment with a time crystal, a very strange quantum system that has revolutionized many fields in physics.
“The double-slit experiment marks the beginning of more complicated temporal modulations. This includes the time crystal, a very strange quantum system that modulates optical properties in a periodic manner. Tirole concludes. “This could have very important applications for light amplification, light control, for example for computation, and maybe even quantum computation with light.”
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