For the first time, scientists have observed quantum interference – a wave-like interaction between particles associated with oddity Quantum entanglement phenomenonOccur between two different types of particles. This discovery could help physicists understand what is going on inside the nucleus of an atom.
Particles act as particles and waves. Interference is the ability of a particle’s wave action to reduce or amplify the action of other quantum particles, like two wake-up boats crossing a lake. Sometimes the overlapping waves add to a larger wave, and sometimes they cancel out the wave, erasing the wave. This overlap occurs because tangle, one of the strangest aspects of quantum physics, predicted in the 1930s and observed experimentally since the 1970s. When entangled, the quantum states of multiple particles correlate so that the measurements of one are related to the measurements of the other, even if one is on Jupiter and the other is on your front lawn.
Dissimilar particles can sometimes become entangled, but until now, such mismatched entangled particles were not known to interfere with each other. This is because part of interferometry It is based on two similar particles that cannot be distinguished from each other. Imagine two photons, or particles of light, from two separate sources. If you were to detect these photons, there would be no way to determine what source each one came from because there is no way to know which photon it is. Thanks to the quantum laws that govern these very small particles, this mystery can be measured: All possible dates for the two identical photons They overlap each other, creating new patterns in the final wave-like actions of the particles.
These patterns do not usually occur with a pair of dissimilar particles, even when they are entangled. Because these particles can be distinguished from one another, there is no mystery about their histories and thus no overlap between these different worlds of possibilities—that is, until now.
First off, physicists have now found interference between two identical subatomic particles. The researchers made the observation at the Relativistic Heavy Ion Collider (RHIC), a massive particle accelerator at Brookhaven National Laboratory on Long Island. This discovery expands the way we understand entanglement and provides new opportunities for using it to study the subatomic world.
says James Daniel Brandenburg, a physicist at Ohio State University who is a member of RHIC’s STAR experiment, where the new phenomenon was seen. This is 10 to 100 times more accurate than previous measurements of high-energy atomic nuclei.
RHIC is designed to collide heavy ions, such as the nuclei of gold atoms. In this case, the researchers were concerned with near misses, not collisions. When gold nuclei shoot at nearly the speed of light through the collider, they create an electromagnetic field that generates photons. When two golden nuclei come close to each other but do not collide, photons may cause neighboring nuclei to become stressed. These near misses were thought of as background noise, says Raghav Konwalkam Eliavali, a Vanderbilt University physicist. Looking at nearby events, Kunnawalkam Elayavalli says, “has opened up a whole new realm of physics that was initially inaccessible.”
When a photon bounces off the nucleus of a neighboring gold ion, it can produce an unusually short-lived particle called rho, which rapidly decays into two particles called pions, one positively charged and the other negatively charged.
A positive pion can interfere with other positive pions caused by other atomic flies. A negative pion can interfere with other negative pions. So far, all this is textbook. But then things get weird: Because the positive and negative pions are entangled, they also interfere with each other. “What they’re doing is something stylistically different in an interesting way,” says Jordan Kotler, a postdoctoral researcher in theoretical physics at the Harvard Society of Fellows who was not involved in the research.. The two-step effect of entanglement and interference doesn’t violate any fundamental rules of quantum mechanics, Kotler says, but is a “smarter” way to extract new information from these particles.
In particular, the photons can act like tiny lasers, scanning the nuclei of gold ions that hit them. These interactions allow researchers to probe subatomic particles such as quarks, which make up the protons and neutrons in an atom, and the gluons that hold quarks together. Physicists still don’t fully understand how protons get properties like mass and spin, the quantum version of angular momentum, from this jumble of entangled particles.
By measuring the momentum of the pions, the researchers can get a picture of the density of the object the photon bounced off — in this case, the subatomic particles that make up the ion’s nucleus. Previous attempts to make these kinds of measurements using other types of particles at high speeds have resulted in a frustratingly blurry picture.
However, STAR scientists recently discovered that the photons in these experiments are polarized, which means that their electric fields travel in a specific direction. This polarization is transmitted to pions and is enhanced by quantum interference, says Yoshitaka Hata, a physicist at Brookhaven National Laboratory who was not involved in the research. By precisely calculating the polarization, the researchers can essentially subtract the “blur” from measurements of the nucleus, resulting in a more accurate image. “We’re actually able to see the difference between where the protons are and where the neutrons are inside the nucleus,” says Brandenburg. He says protons tend to cluster in the center, surrounded by a “skin” of neutrons.
Beyond the size of the kernel, there are other details this technique can reveal. For example, the spin of the proton outweighs the spin of the quarks that make up the proton, which means that something unknown inside the proton explains the rest of the spin. The gluons holding the quarks together are most likely the culprit, Brandenburg says, but scientists haven’t yet found a good way to tell what they’re up to. Going forward, the new technique could allow a clearer look at gluons’ spin and other properties.
“What’s so fascinating is that these contemporary experiments continue to push the boundaries of our understanding of quantum mechanics and measurement and open up new avenues for both theory and experiment,” Kotler says.