One of the things that sets the quantum world apart from our everyday classical world is the ability to entangle. That is, when two or more objects share an invisible connection and their destinies are intertwined. Entanglement is the most extreme version of quantum connectivity, where measuring one particle can tell you all the information you need to know about another particle. Aside from that, the particles can be synchronized in an apparently quantum way: measuring one particle gives imperfect information about another particle. It can be used to make more accurate measurements than For example, it helps detect gravitational waves.
Photons of light don’t often combine naturally in this way. However, when it does, quantum correlated photons could be useful in studying the quantum properties of materials. But generating this quantum light is a difficult task and so far has been largely confined to just a few photons.
Electrons, atoms and molecules, on the other hand, are always involved in collective quantum correlations inside matter. For example, when electrons synchronize inside metals, superconductivity occurs at low temperatures, and physicists have speculated high-temperature superconductivity, exotic fractional-electron materials, and more. Now, a team of physicists from Israel, Austria, England, and the United States has found a way to imprint light with complex patterns of quantum correlations from such matter.The method can produce bright quantum light over a wide range of frequencies, the team recently explained. natural physics.
“Imagine that there is quantum light that the eye can see,” says Ido Kaminer, an electrical and computer engineer at the Technion-Israel Institute of Technology and senior author of the study. “It’s amazing, and it has many advantages for the application of quantum science that we wouldn’t have thought otherwise.”
The researchers’ ideas build on existing processes for creating bright bursts of light. In this process, known as harmonic generation, a bright laser beam is directed at an atomic gas or, more recently, a solid crystal such as zinc oxide, the active ingredient in many mineral sunscreens. Gas atoms or solids absorb laser light and then emit light at harmonics. If the input light is like the middle C on a piano, the emitted light is comparable to many C notes hundreds of octaves up.
The radiation combines to create a light pulse that travels in a fraction of a second (one billionth of a billionth). When directed at electrons, atoms, or molecules, these short bursts can be used to capture high frame rate video.
In their new work, the researchers aimed to understand how quantum correlations within the source material, be it a gas or a mineral, affect the quantum properties of the emerging light burst. Development is a very important area, yet until recently it was described in classical light paintings,” Kaminer says.
In quantum mechanics, it is notoriously difficult to understand what is happening with multiple particles at the same time. Kaminer and his graduate student in his lab, Alexey Gorlach, sought to take advantage of the quarantine imposed by COVID to advance a full quantum description of light emitted at harmonics. It’s really crazy. Alexey has built a very complex mathematical description on an unprecedented scale,” he says Kaminer.
Next, to fully incorporate the quantum properties of the materials used to generate this light, Kaminer and Gorlach teamed up with Andrea Pizzi, then a graduate student at Cambridge University and now a postdoctoral fellow at Harvard University. assembled.
“It’s a very beautiful mathematical framework for attacking the very tricky mesoscopic world,” says Elena del Valle, an expert on the interaction of light and matter and a physicist at the Autonomous University of Madrid. increase. “Mesoscopic” refers to a combination of moderate numbers of particles. More than a few, but not so many that individual behavior is completely irrelevant. Here we mean many photons and their quantum correlations.
The researchers’ results describe precisely how the quantum correlation of the light source translates into the quantum correlation of the emitted light.
If such quantum light can be successfully generated in experiments, there are two main avenues for practical application. First, it gives you insight into the material that produced it. “Quantum properties are at the heart of many things, such as high-temperature superconductors,” says Kaminer. “And this will tell you something you wouldn’t have seen otherwise.”
Second, quantum light can be used as a light source, especially for X-ray imaging. In this region, correlated light can acquire additional quantum information that is otherwise inaccessible. “Once we get to the X-ray region, we can use it to image the material and pass the sample through,” he says.
The atoms and materials used today to generate harmonics don’t have interesting quantum properties and don’t produce quantum light, says Kaminer. To select the materials to use and create this light in the lab, scientists aim to team up with experimental groups. They warn that the actual implementation may not be trivial.
“From here to experimentation still requires some hard work, innovative engineering and theoretical development,” says Pizzi. But researchers have some promising experimental ideas, and Pizzi and his collaborators, as well as others in the field, are optimistic. “Putting all this together for a few atoms under intense pulsed excitation is not science fiction at this point,” Del Valle says. This technology could give scientists an unprecedented glimpse into the full quantum complexity of matter.
