Scientists observe quantum interference — wave-like interactions between particles associated with exotic phenomena — for the first time quantum entanglement– Occurs between two different particles. The discovery could help physicists understand what’s going on inside the nucleus.
Particles act as both particles and waves. Interference is the ability of one particle’s wave-like action to weaken or amplify the action of other quantum particles, like the sterns of two boats navigating a lake. Sometimes overlapping waves add up to create a larger wave, and sometimes they cancel each other out, eliminating the wave.This interference occurs because to entangle, which is one of the stranger aspects of quantum physics, was predicted in the 1930s and has been observed experimentally since the 1970s. When entangled, the quantum states of multiple particles are correlated, so that measurements of one particle will correlate with those of the others, even if one particle is on Jupiter and the other is on your front lawn .
Different particles are sometimes entangled with each other, but until now, it was not known that these mismatched entangled particles could interfere with each other.that’s partly because Measure interference Rely on two wavy particles that are indistinguishable from each other. Imagine two photons, or particles of light, coming from two different sources. If you were to detect these photons, you wouldn’t be able to tell which source each photon came from, because there’s no way to tell which photon is which. This ambiguity is actually measurable thanks to the quantum laws that govern these very small particles: All possible histories of two identical photons Interfere with each other, creating new patterns in the resulting wave-like motion of the particles.
These modes don’t usually occur on a pair of distinct particles, though, even when they’re entangled. Because these particles can be distinguished, their histories are not mysterious, so there is no interference between these different possible worlds — that is, until now.
First, physicists have now detected interference between two different subatomic particles. The researchers made the observations at the Relativistic Heavy Ion Collider (RHIC), a massive particle accelerator at Brookhaven National Laboratory on Long Island. This discovery broadens the way we understand entanglement and offers new opportunities to use it to study the subatomic world.
“Using this new technique, we were able to measure the size and shape of atomic nuclei down to one-tenth the size of a femtometer, which is one-tenth the size of a single proton,” said Ohio State University physicist James Daniel Brandenburg. RHIC’s Member of the STAR experiment, where new phenomena were discovered. This is 10 to 100 times more precise 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, though, the researchers were interested in near misses, not collisions. As the gold nuclei pass through the collider at close to the speed of light, they generate an electromagnetic field that produces photons. When two gold nuclei come close to each other but do not collide, photons may hit the adjacent nuclei. STAR collaborators Raghav Kunnawalkam Elayavalli, a physicist at Vanderbilt University, said these near misses used to be considered background noise. But observing these breathtaking events “opens up a whole new field of physics that was initially inaccessible,” says Kunnawalkam Elayavalli.
When a photon bounces off the nucleus of a neighboring gold ion, it produces an extremely short-lived particle called a rho, which rapidly decays into two particles called pions, one positively charged and one negatively charged .
Pions interfere with other positons caused by flybys of other atoms. Negative mesons interfere with other negative mesons. All of this is textbook so far. But then things got weird: Because positive and negative mesons are entangled, they also interfere with each other.”What they’re doing is stylistically different in an interesting way,” said Jordan Kotler, a postdoctoral fellow in theoretical physics at the Harvard Society of Fellows, who was not involved in the study. The two-step effect of entanglement and interference doesn’t violate any of the fundamental rules of quantum mechanics, Kotler says, but is a “smarter” way to extract new information from these particles.
In particular, photons can scan the nuclei of gold ions they collide with like tiny lasers. These interactions allow researchers to probe subatomic particles such as quarks, which make up protons and neutrons in atoms, and gluons, which hold quarks together. Physicists still don’t fully understand how protons acquire properties such as mass and spin, the quantum version of angular momentum, from this entangled particle.
By measuring the muon’s momentum, the researchers can obtain 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 such measurements using other types of high-speed particles have resulted in frustratingly blurry images.
However, STAR scientists recently discovered that the photons in these experiments were polarized, meaning their electric field traveled in a specific direction. This polarization is passed on to the muons and enhanced by quantum interference, says Yoshitaka Hatta, a physicist at Brookhaven National Laboratory who was not involved in the study. By calculating the polarization precisely, the researchers can essentially subtract the “blur” from the nuclear measurements, resulting in a more accurate image. “We were actually able to see the difference between where the protons are inside the nucleus and where the neutrons are inside the nucleus,” Brandenburg said. Protons tend to cluster in the center, surrounded by a “skin” of neutrons, he said.
In addition to the size of the nucleus, the technique can reveal other details. For example, the spin of the proton exceeds the spin of the quarks that make up the proton, which means that there is something unexplained inside the proton that could explain the rest of the spin. The gluons that bind the quarks together could be the culprit, Brandenburg said, but scientists haven’t figured out a good way to figure out what they’re doing. Going forward, this new technique could give us a clearer picture of the spin and other properties of gluons.
“Fantastically,” said Kotler, “these contemporary experiments are still pushing the boundaries of our understanding of quantum mechanics and measurement, and opening new horizons for theory and experiment.”