In Erwin Schrödinger's most famous thought experiment, a cat is seemingly able to be alive and dead simultaneously, as it exists in superposition within a closed box alongside a radioactive atom, a detector, a hammer, and a vial of poison.
Now, reaching into similar mind-bending territory that blurs the lines between practical science and science fiction, researchers in China report in a new study that they have successfully used nonlocal artificial materials to create what they call "photonic parallel spaces," emulating the effects of wormholes, and even multiple realities.
At the heart of the new research are optical systems, in which a single material is able to perform the role of two distinct optical devices at the same time -- not unlike the bizarre "superposition" of Schrödinger's cat -- whereby light is able to display multiple properties at once.
The experiments, detailed in a new paper in Nature Communications, allowed the researchers to produce invisible pathways and other optical effects that could pave the way toward the creation of a range of new technological applications in the coming years.
"The concepts of the multiverse and wormholes in dimensions beyond our physical space have long captivated curiosity and imagination," the authors of the new paper write. However, demonstrating such ideas in an experimental setting has long been challenging.
To overcome such hurdles, the research team relied on special artificial materials that allowed them to develop what they characterize as a "photonic analogy" of parallel spaces, which they describe as conditions where "two distinct effective optical media coexist within a single artificial material," each of which is accessible using different boundaries in the respective material.
The team's method, which was complemented with machine learning for their study, successfully helped them to create analogies for what they call "photonic wormholes," which function as invisible optical tunnels, as well as "photonic multiple realities" where the independent function of two different optical devices occurred within a single location. The effect, the researchers describe, produced optical scatterers that functioned "as if they exist in separate dimensions."
When light enters one boundary in the artificial materials used by the team, it experiences an entirely different set of optical effects compared with light entering from another boundary. Surprisingly, each of these optical experiences can occur without any interference between them.
The researchers liken this effect to C.S. Lewis's classic, The Lion, the Witch, and the Wardrobe, where different "doors" could lead to entirely separate worlds located in a single place.
Yun Lai, a professor from the school of physics at Nanjing University and one of the paper's corresponding authors, said this effect "lets us emulate higher-dimensional phenomena in a photonic lab."
"It's like hosting two optical realities in one material," Lai said, adding that such capabilities could potentially enable new technologies that were previously unimaginable.
In the team's first set of experiments, researchers were able to produce a "wormhole" effect using an elongated nonlocal artificial material, through which a beam of electromagnetic radiation known as a Gaussian beam is fired through the invisible optical tunnel's shorter side.
Passing through the "wormhole," the beam is confined as though passing through a waveguide possessing a refractive index (referring to how much the path of light is bent) of zero.
By comparison, when entering the long side of the material, the beam was found to show near-zero reflection, which allowed it to become functionally invisible to external light.
Additionally, the researchers say they were able to demonstrate what they call "photonic multiple realities," in which the same material seemed to mimic the properties of other kinds of optical technologies, depending on which entry boundary was used.
During one experiment, the material was able to scatter light in ways a boat-shaped object might achieve, while behaving like a tree-shaped light scatterer in another example.
By creating analogies for these unusual phenomena, the researchers report that the optical properties they have observed in their experiments could help researchers "transcend the limitations of physical dimensions," which may ultimately offer a path toward the creation of unparalleled multi-purpose technologies.
While the results of the team's mind-bending experiments may be a bit difficult to grasp, Lai says that what he and his colleagues have achieved are really just practical counterparts to these strange sci-fi concepts.
"We're not building real wormholes or multiverses," Lai said in a statement, "but we're making these concepts practical for engineering."
Lai adds that such applications could potentially reshape several technological fields "by leveraging nonlocality as a new degree of freedom."
Fundamentally, by simulating the effects of higher-dimensional physics, Lai and the team's work could open new avenues toward the creation of technologies that extend well beyond normal dimensional constraints, potentially revolutionizing the field of photonics and related areas.
The team's recent paper, "Nonlocality-enabled photonic analogies of parallel spaces, wormholes and multiple realities," was published in Nature Communications.