Stephanie Pappas
Sun, August 13, 2023
Illustration of atomic orb.
For the first time, researchers have observed "quantum superchemistry" in the lab.
Long theorized but never before seen, quantum superchemistry is a phenomenon in which atoms or molecules in the same quantum state chemically react more rapidly than do atoms or molecules that are in different quantum states. A quantum state is a set of characteristics of a quantum particle, such as spin (angular momentum) or energy level.
To observe this new super-charged chemistry, researchers had to coax not just atoms, but entire molecules, into the same quantum state. When they did, however, they saw that the chemical reactions occurred collectively, rather than individually. And the more atoms were involved, meaning the greater the density of the atoms, the quicker the chemical reactions went.
"What we saw lined up with the theoretical predictions," Cheng Chin, a professor of physics at the University of Chicago who led the research, said in a statement. "This has been a scientific goal for 20 years, so it's a very exciting era."
Related: What is quantum entanglement?
"What we saw lined up with the theoretical predictions," Cheng Chin, a professor of physics at the University of Chicago who led the research, said in a statement. "This has been a scientific goal for 20 years, so it's a very exciting era."
The team reported their findings July 24 in the journal Nature Physics. They observed the quantum superchemistry in cesium atoms that paired up to form molecules. First, they cooled cesium gas to near absolute zero, the point at which all motion ceases. In this chilled state, they could ease each cesium atom into the same quantum state. They then altered the surrounding magnetic field to kick off the chemical bonding of the atoms.
These atoms reacted more quickly together to form two-atom cesium molecules than when the researchers conducted the experiment in normal, non-super-cooled gas. The resulting molecules also shared the same quantum state, at least over several milliseconds, after which the atoms and molecules start to decay, no longer oscillating together.
"[W]ith this technique, you can steer the molecules into an identical state," Chin said.
The researchers found that though the end result of the reaction was a two-atom molecule, three atoms were actually involved, with a spare atom interacting with the two bonding atoms in a way that facilitated the reaction.
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This could be useful for applications in quantum chemistry and quantum computing, as molecules in the same quantum state share physical and chemical properties. The experiments are part of the field of ultracold chemistry, which aims to gain incredibly detailed control over chemical reactions by taking advantage of the quantum interactions that occur in these cold states. Ultracold particles could be used as qubits, or the quantum bits that carry information in quantum computing, for example.
The study used only simple molecules, so the next goal is to attempt to create quantum superchemistry with more complex molecules, Chin said.
"How far we can push our understanding and our knowledge of quantum engineering, into more complicated molecules, is a major research direction in this scientific community," he said.
This article was provided by Live Science.
Could white holes actually exist?
Paul Sutter
Sun, August 13, 2023
graphic illustration showing a black hole above and a white hole below.
Black holes seem to get all the attention. But what about their mirror twins, white holes? Do they exist? And, if so, where are they?
To understand the nature of white holes, first we have to examine the much more familiar black holes. Black holes are regions of complete gravitational collapse, where gravity has overwhelmed all other forces in the universe and compressed a clump of material all the way down to an infinitely tiny point known as a singularity. Surrounding that singularity is an event horizon, which is not a physical, solid boundary, but simply the border around a singularity where the gravity is so strong that nothing, not even light, can escape.
We know how the universe forms black holes. When a massive star dies, its immense weight crushes onto its core, triggering the creation of a black hole. Any matter or radiation that wanders too close to the black hole gets trapped by the strong gravity and pulled beneath the event horizon to its ultimate doom.
Related: What happens at the center of a black hole?
We understand this process of black hole formation, and how black holes interact with their environments, through Einstein's theory of general relativity. To arrive at the concept of a white hole, we have to recognize that general relativity doesn't care about the flow of time. The equations are time-symmetric, meaning the math works perfectly fine running forward or backward in time.
So if we were to take a movie of the formation of a black hole and run it in reverse, we would find an object streaming radiation and particles. Eventually, it would explode, leaving behind a massive star. This is a white hole, and according to general relativity, this scenario is perfectly fine.
White holes would be even stranger than black holes. They would still have singularities at their centers and event horizons at their borders. They would still be massive, gravitating objects. But any material that entered a white hole would immediately get ejected at a speed greater than that of light, causing the white glow to shine ferociously. Anything on the outside of a white hole would never be able to get inside it, because it would have to travel faster than the speed of light to cross inward through the event horizon.
But if white holes are allowed by the math of general relativity, then why don't we suspect that they exist in the real universe? The answer is that general relativity is not the only word on the cosmos. There are other branches of physics that tell us about the inner workings of the universe, like our theories of electromagnetism and thermodynamics.
Within thermodynamics, there is the concept of entropy, which is, very roughly speaking, a measure of the disorder in a system. The second law of thermodynamics tells us that the entropy of closed systems can only go up. In other words, disorder always increases.
As an example, say you throw a piano into a wood chipper. Out comes a bunch of pulverized debris. Disorder in the system has increased, and the second law of thermodynamics has been satisfied. But if you throw a bunch of random pieces into that same wood chipper, you won't get a fully formed piano out of it, because that would cause disorder to decrease. (Highly ordered systems, like life, can arise on Earth — but they come at the cost of increased entropy within the sun. You're still not getting pianos out of wood chippers, no matter how you construct your system.)
We can't simply run the process of black hole formation in reverse and get a white hole, because that would cause entropy to decrease — stars don't miraculously appear out of gigantic cosmic explosions. So, while general relativity is agnostic about the reality of white holes, thermodynamics gives the concept a hard no.
The only way to form a white hole would be to have some exotic process operating in the early universe that baked the existence of a white hole into the fabric of space-time itself. That way, the white hole formation process would bypass the trouble with decreasing the entropy — the white hole would simply be there, existing, since the beginning of time.
a fuzzy donut shape with a dark center and blurry orange ring.
The Event Horizon Telescope, a planet-scale array of eight ground-based radio telescopes forged through international collaboration, captured this image of the supermassive black hole in the center of the galaxy M87 and its shadow. Here M87 is viewed in polarized light. (Image credit: EHT Collaboration)
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Unfortunately, white holes would also be fantastically unstable. They would still gravitate and pull material toward them, but nothing would be able to cross the event horizons. As soon as anything, even a single photon (particle of light) approached a white hole, it would be doomed. If the particle approached the event horizon, it would not be able to cross it, sending the energy of the system skyrocketing. Eventually, the particle would have so much energy that it would trigger the collapse of the white hole into a black hole, ending its existence.
So, as fun and mind-bending as white holes appear to be, they do not seem to be features of the real universe — just ghosts haunting the mathematics of general relativity.
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