Yes, I deliberately misspelled “trifecta” in the heading (actually, it was a typo, but turned out to be appropriate). First is a short video from The Dodo about a woman who tamed a very wary feral cat—with her hair! It took three years.
The mystery is why Spooky liked the smell of the woman’s hair but was wary of the smell of her body.
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And an article from IFL Science (you know what the “IFL” stands for) discussing an experiment by seven Chinese researchers who created a superposition state lasting for 23.3 minutes. You probably remember that the Schrödinger’s Cat thought experiment involved an implication of the “Copenhagen interpretation” of quantum mechanics. Here’s a description of the experiment by Wikipedia and a drawing of it:
In Schrödinger’s original formulation, a cat, a flask of poison, and a radioactive source are placed in a sealed box. If an internal radiation monitor (e.g. a Geiger counter) detects radioactivity (i.e. a single atom decaying), the flask is shattered, releasing the poison, which kills the cat. The Copenhagen interpretation implies that, after a while, the cat is simultaneously alive and dead. Yet, when one looks in the box, one sees the cat either alive or dead, not both alive and dead. This poses the question of when exactly quantum superposition ends and reality resolves into one possibility or the other.
Although originally a critique on the Copenhagen interpretation, Schrödinger’s seemingly paradoxical thought experiment became part of the foundation of quantum mechanics. The scenario is often featured in theoretical discussions of the interpretations of quantum mechanics, particularly in situations involving the measurement problem. As a result, Schrödinger’s cat has had enduring appeal in popular culture. The experiment is not intended to be actually performed on a cat, but rather as an easily understandable illustration of the behavior of atoms. Experiments at the atomic scale have been carried out, showing that very small objects may exist as superpositions; but superposing an object as large as a cat would pose considerable technical difficulties.
The “Copenhgagen interpretation” of quantum mechanics, the one held by Bohr, Heisenberg, and many other founders of the field, sees q.m. as inherently indeterministic, involving only probabilities that certain states will occur. Schrödinger apparently thought the idea that a cat could be in a superposed state of being both alive and dead at the same time was ludicrous, so the feline Gedankenexperiment was really a critique of the Copenhagen interpretation. But it’s become part of the Copenhagen interpretation as far as I understand, with the boxed cat both alive and dead at the same time, and the superposition (wave function) resolved only when the cat is observed when the box is opened.
There are other interpretations of this experiment, notably the “many-worlds” theory, in which there is no superposition, but a splitting of the universe when the experiment is conducted, with the cat alive in one universe and dead in the other. Don’t ask me which interpretation is “right”!
No cats were superposed in any experiments. But according to the experiment described below, the experiment was performed on an isotope of the metallic element Ytterbium, kept in superposition (having opposite spins at the same time) for over 23 minutes. IFL Science gives a summary (click headline to read):
Excerpt:
States in quantum superposition are notoriously fragile but researchers in China have reported creating such a state that lasted for a whopping 23 minutes and 20 seconds. This record-breaking result is exciting in itself but the team believes that it could open new ways to high-precision measurements and even information processing for quantum computers – possibly even allowing scientists to probe the limits of physical theories.
The study, which is yet to be peer-reviewed, conducted by scientists at the University of Science and Technology of China, saw 10,000 atoms of ytterbium cooled down to a few thousandths of a degree above absolute zero and trapped using light. Each atom could be controlled with great accuracy and was put into the superposition of two very different spin-states. This is known as a “quantum cat” state.
In the famous Schrödinger’s cat thought experiment, we see a cat closed in a box with a poison activated by a random quantum process. Without opening the box we cannot ascertain the state of the cat, so it is both alive and dead, two contradictory states in the non-quantum reality we experience. In the quantum world, quantum cat states are superpositions where a quantum state can exist in several ways at once, although it’s impossible to tell which one it really is so it’s effectively all of them at once.
In the new experiment, it is the length of this quantum cat state that is astounding. In nature, the superposition will collapse into one or the other in a fraction of a second, but here it persisted for 1,400 seconds. The team thinks that with a better vacuum system, it can be made to last even longer.
“It’s a big deal because they’re making this beautiful cat state in an atomic system and it’s stable,” Barry Sanders, from the University of Calgary who was not involved in the study, told New Scientist. “A probe gets jiggled and pushed and nudged and prodded, and then by seeing what happens, you learn about the things that interact with it.”
Here’s a screenshot of the paper’s title from Arχiv (click to read). I’ve put its abstract below, but good luck understanding it!
The abstract:
Quantum metrology with nonclassical states offers a promising route to improved precision in physical measurements. The quantum effects of Schr{ö}dinger-cat superpositions or entanglements allow measurement uncertainties to reach below the standard quantum limit. However, the challenge in keeping a long coherence time for such nonclassical states often prevents full exploitation of the quantum advantage in metrology. Here we demonstrate a long-lived Schr{ö}dinger-cat state of optically trapped 173Yb (\textit{I}\ =\ 5/2) atoms. The cat state, a superposition of two oppositely-directed and furthest-apart spin states, is generated by a non-linear spin rotation. Protected in a decoherence-free subspace against inhomogeneous light shifts of an optical lattice, the cat state achieves a coherence time of 1.4(1)×103 s. A magnetic field is measured with Ramsey interferometry, demonstrating a scheme of Heisenberg-limited metrology for atomic magnetometry, quantum information processing, and searching for new physics beyond the Standard Model.
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Finally, one more example, from ZME Science, of a cat aiding scientific discovery. This wouldn’t have happened if the cat’s staff didn’t include a scientist, which helped identify a new virus in a mouse caught by his moggie. Click to read:
An excerpt:
It’s not uncommon for cats to bring home “spoils” from their hunt — usually a mouse, lizard, or some other unlucky creature. So, it wasn’t a shock when Pepper, a Florida cat, came back with a cotton mouse (Peromyscus gossypinus). But Pepper’s owner, John Lednicky, is a microbiologist and virus hunter at the University of Florida. So rather than toss out the rodent, Lednicky brought it to his lab. And there, he made an unexpected discovery: a previously unknown virus.
. . . Lednicky and his team initially tested the mouse to see if it carried mule deerpox virus (MDPV), a pathogen that has recently spread through Florida and a few other US states. Instead, they discovered something completely new.
By using next-generation sequencing technology, the researchers decoded the virus’ genome and classified it within the paramyxovirus lineage.
Paramyxoviruses belong to a larger group called Jeilongviruses. This family includes viruses responsible for measles and mumps in humans, as well as severe animal diseases like Hendra and Nipah. The newly identified virus, named GRJV1, exhibited an ability to infect various mammalian cell types, from rodents to humans. This broad “cell tropism” suggests the virus could potentially spill over from animals to humans or other mammals, which raises some concerns.
The lesson: don’t handle wild mice! And don’t buy mice in the wet market!
Here’s a three-minute video of the discovery:
Lagniappe: A 6-7 year old injured street cat makes a miraculous recovery:
Street cat was as light as a kitten when he was rescued — watch him get chubby and gorgeous and knead on his new mom nonstop 🧡 pic.twitter.com/jrKPmyWjIv
— The Dodo (@dodo) November 18, 2021
h/t: Ginger K.
Feynman famously said “If you think you understand quantum physics, you don’t understand quantum physics. The late Steven Weinberg, who was about as expert as anyone in the world on quantum matters, always bluntly stated he did not intuitively understand QM.
Consider the mathematically simplest possible quantum situation, the two state quantum system that describes electron spin or photon polarization. I can confidently claim to understand the math PERFECTLY. But even in that simple situation my mind boggles when I try to intuitively grasp what the simple math is really saying about reality.
I take the pessimistic view that we can’t understand QM, not because we’re not smart enough, but because human brains simply aren’t wired for the task. Our hunting and gathering ancestors had to intuitively grasp aspects of Newtonian physics well enough to erect huts, throw spears, and invent bows and arrows and hunting darts and boomerangs and such. But before the twentieth century never ever did hominids need to trouble their minds about quantum superpositions.
To make an analogy, I could study in agonizing mathematical detail the data a bat gets about the world from its sonar and echolocation, but I could not integrate the data into a perception of the world the way a bat’s brain can do. My brain doesn’t swing that way. The bat of course, even if it could be as intelligent as me, could make no sense of my visual understanding of the world. (I know, bats aren’t really blind. In fact they have good night vision. But in most respects their vision is rudimentary compared to the vision of a primate.) In the same way I can study a quantum situation, even a fairly complicated one, and master the relevant mathematical details. But I can’t put it together to get a conceptual understanding of the reality that is described by the math.
I simply have no idea how to best interpret Schödinger’s cat situations. I can calculate stuff and predict outcomes of experiments, but that is different than intuitively understanding a damn thing.
Schrödinger’s point was that a cat cannot be described by a single wave function. Actually it can, in the sense that all of the individual wave functions that make up a cat can be added to make up the description of a whole cat. However, decoherence means that that description jumbles up after a very short time: the wave functions go their own ways and devolve into an incoherent mess. So Schrödinger was essentially correct.
Sure. Decoherence is realistically what happens. But in Schrödinger’s thought experiment one assumes the idealized case that the interior of the box containing the apparatus and the cat is completely isolated from the rest of the universe. In that case decoherence does not occur and the superposition of the live and dead states of the cat persists indefinitely.
Decoherence is applied in two ways. In the many worlds interpretation it is invoked to claim that everything contributes to the wave function of the universe. In the consistent histories interpretation decoherence essentially says that everything disconnects. That latter favours Schrödinger’s point.
THE Richard Bond?
Who he? I am inconsequential.
There is a relatively well known cosmologist/astrophysicist named J. Richard Bond.
https://en.wikipedia.org/wiki/Dick_Bond_(astrophysicist)
The one in this world, not to be confused with the many other Richard Bonds in the many other worlds.
Like it!
Ha!
Bond. Richard Bond.
The poor cat, being held in a quantum state for so long. Oh, the humanity!
I took your challenge to understand the abstract of the article, and I think that I (sorta, kinda) do understand—at least I understand the words. :-). The meaning? Not so much. I’ve read a lot of articles on this general topic. If you read popular books in physics, you can’t escape Schrödinger’s cat—the poor thing.
I had a good friend, I. J. (“Jack”) Good, a British statistician with whom I wrote a few papers. His work was highly mathematical, so much so that it took me many, many hours to “understand” his one-page article in Nature on the fast-Fourier transform. When I told him about my difficulty, he told me that “Mathematics isn’t something you understand; it’s something you get used to.” I feel that the same applies to quantum mechanics. So do lots of physicists, apparently, as their “Shut up and calculate” advice implies: https://en.wikipedia.org/wiki/Copenhagen_interpretation.
Enjoyed the Caturday and reading the comments too.
The IFLScience looks very interesting, but I couldn’t find what IFL means on their site. I’ve decided to subscribe, so thanks for the tip, Jerry.
My guess: “I Feel Like Science”
I F*cking Love Science.
I entered it to Google and got “in fake life.”
But it seems Mark is right.
Wikipedia says it’s not always accurate and doesn’t give corrections.
Being a “curious layperson” and not a scientist, I came to a similar view. Interpretations of QM seem to be somewhat desperate attempts to describe a ball to flatlanders. For example, in many-worlds, anything that can happen, literally does happen – per evolution of the universal wave function. From temporal viewpoint, every Universe that could have arised from the Big Bang, did indeed arise. But we have no contact with those other Universes; they are realities complete within themselves. If we don’t and can’t have any interaction with other Universes of MWI, does it make sense to talk about them as “real”? I can’t even control which Universe I will personally end up in, although some people try prayer – with mixed results. 😉
This is all pretty well over my pay grade, but my gut tells me that the Many Worlds hypothesis must be impossible because of thermodynamics. If new universes are splitting off at every point in space and at every point in time, well, all that matter needs to come by converting energy from something. Where does the energy come from? The energy conversion should also make all universes really really hot at all times.
Anyway, that is what this version of me is typing right now.
It is plausible that the net energy of a universe is zero: energy associated with matter is cancelled by negative gravitational energy. So the many worlds hypothesis does not fail on that count.
My main objection to it is that it is usually explained in terms of a two-way splitting, or at least a discrete number of splits. However, the single photon/electron of Young’s slit experiment shows that the final position of a particle is a continuum, so a single particle undergoing diffraction would create an infinity of other worlds. Also, Everett’s concern was to get rid of probability, but probability still exists in which world one finds oneself.
Why Spooky liked the smell of the woman’s hair? There was probably an ingredient in the shampoo that he reacted to.
And didn’t like her body wash.
As a cat person, I was happy to notice that sometimes when Sean Carroll describes the thought experiment, instead of a lethal gas being released it’s a safe sleeping-gas, and the cat’s two states are given as awake and asleep.
“… superposing an object as large as a cat would pose considerable technical difficulties.”
You think? Have you ever tried to give a cat a bath?
I have a variation on the experiment. It has a special sleep-inducer that is pointed at you, the one reading these words, a radioactive source, and an internal radiation monitor, all in a sealed box. If the monitor detects radiation, the sleep-inducer is triggered and you instantly become unconscious. Tell me, are you in a superposed state of simultaneously conscious and unconscious right now? What’s that like?
I accept Schrödinger’s critique: while the theory may be a pinnacle achievement of humanity, the explanations are nonsensical. I take that to mean simply that we don’t understand it, however accurate the math is.
Which is fine. Perhaps a cogent explanation will be found. Perhaps a new mathematical description will supersede it that is explainable. Perhaps it will be entirely forgotten when a new, more accurate, more explainable theory takes its place.
Science marches on and we watch in wonder.
I never understood why the cat doesn’t count as an observer, which therefore collapses the wave function. Are humans so very special?
Question: When we die is that a form of dechoherence of the brain?