Okay, this is WAY above my pay grade, but I’ve been sent articles on this by several authors, including an explanation at the Guardian. It’s a description by two theoretical physicists of an experiment that uses quantum superposition to put a bacterium in two places at the same time. They plan to collaborate with experimentalists to actually carry it out. Here’s what the Guardian says about it:
The researchers plan to build on the work of others at the University of Colorado who showed in 2013 that a tiny, vibrating aluminium membrane could be placed in a superposition of states.
“We propose to simply put a small microbe on top of the aluminum membrane. The microbe will also be in a superposition state when the aluminum membrane is in a superposition state. The principle is quite simple,” Dr Li said.
The researchers plan to go one step further in a second experiment that would entangle the position of the microbe with the spin of an electron inside it. “The purpose of the second experiment is to make the system useful. It can be used to detect defects of DNA and proteins in a microbe, and image the microbe with single electron spin sensitivity,” Dr Li said.
Li said he hoped to conduct the experiment, but that leading scientists in the field had laboratories better equipped to take the project on, and that he hoped to collaborate with them. “If the top group in quantum electromechanics want to focus on doing this experiment, I think a microbe could be put into a superposition state in three years,” he said.
The experiment is proposed in a paper by Tongcang Li and Zhang-Qi Yin (full pdf here) placed at ArXiv before publication. The abstract:
Schrödinger’s thought experiment to prepare a cat in a superposition of both alive and dead states reveals profound consequences of quantum mechanics and has attracted enormous interests. Here we propose a straightforward method to create quantum superposition states of a living microorganism by putting a small bacterium on top of an electromechanical oscillator. Our proposal is based on recent developments that the center-of-mass oscillation of a 15-μm-diameter aluminium membrane has been cooled to its quantum ground state [Nature 475, 359 (2011)], and entangled with a microwave field [Science, 342, 710 (2013)]. A microorganism with a mass much smaller than the mass of the electromechanical membrane will not significantly affect the quality factor of the membrane and can be cooled to the quantum ground state together with the membrane. Quantum superposition and teleportation of its center-of-mass motion state can be realized with the help of superconducting microwave circuits. More importantly, the internal states of a microorganism, such as the electron spin of a glycine radical, can be prepared in a quantum superposition state and entangled with its center-of-mass motion. Our proposal can be realized with state-of-art technologies. The proposed setup is also a quantum-limited magnetic resonance force microscope (MRFM) that not only can detect the existence of an electron spin, but also can coherently manipulate and detect the quantum state of the spin.
And here’s the diagram of the experiment from the paper:
Because this is all beyond my ken, I asked Official Website Physicist™ Sean Carroll for a comment on the feasibility of the experiment. (Note that Sean is giving the famous Gifford Lectures next year and has an intriguing Book on Everything coming out next May). His take:
As far as Schrödinger’s microbe is concerned — there’s no problem in principle, though I am quite dubious in practice. Quantum mechanics says that things can be in superpositions of different locations, and everything in the world (including bacteria) is governed by the rules of quantum mechanics, so it’s certainly conceivable.The problem is that to count as a “superposition” you need to keep the system unentangled from the rest of the world — once the thing interacts with the environment, the superposition branches the whole wave function of the universe (the phenomenon known as “decoherence”). That’s why we can’t even imagine doing it for real cats; they’re always breathing and radiating heat and so forth, thereby interacting with their environments. It seems to me that the same would be true for a bacterium, or anything else that we would qualify as “alive” — unless you were talking about very short time periods indeed. (I’d be much less skeptical if it were a freeze-dried bacterium.) Note that the paper is a theoretical proposal, not an experimental result.
h/t: Grania
Impossible. Superposition of matter over macroscopic distances (>1 um) with greater than 10^9 particles not all occupying the same coherence state…impossible.
If demonstrated, it would effectively overthrow a probability of something like >>1/10^20 assuming our general understanding of quantum mechanics holds. And a cell has many more particles than 10^9!
Just as a side note, Tongcang is brilliant (I have co-authored papers with him) and if there is anyone who is probably going to push the boundary of classical-quantum transition and the limits of decoherence it would probably be him.
I am not sure that I understand the description of the proposed experiment correctly*, but it seems to say that the “center of mass” will be put into a superposition of states, not the entire bacterium.
Actually I am very sure that I don’t have a good understanding of the proposed experiment.
That’s where I lost it, too. I’m more comfortable thinking in terms of wave functions that describe individual particles in superpositions of states… but never heard of an abstraction like a “center of mass” being so described.
The claim seems to be that it’s already been done successfully with an oscillator substantially more massive than the bacterium:
I think the cool thing about the idea is that it utilizes the negligible contribution of adding a small virus (or such) to a micro mechanical resonator.
From a theoretical standpoint, this is interesting because maybe it means that mass bears no limit to decoherence in space or time?? This is doubly interesting because both general relatively and QM are interested in things that have measurable mass (but that is another story; cf. works of Tony Leggett and Frank Wilczek on the subject).
Technically, there appears to be no roadmap suggested by the paper for macroscopic entanglements that would necessarily imply coherence times greater than 100 us or lengths greater than ~1000 um for massive objects.
I’m more skeptical about the active metabolism than I am the number of particles. Haven’t others already done successful superposition experiments with structures like buckeyballs? I know this is still orders of magnitude larger but the fact that they’ve done it with an aluminum membrane tells me that intermediate sized (between, say, nm and a few microns) crystalline solids and things with fairly simple, stable molecular structures may not be a big issue. A bacterium, however, isn’t that. Its chemically very active, which poses a very large problem for an experiment with the requirement “nothing can interact with these atoms.”
I think, if anything, there is very little difference between entangling a block of water ice the size of a Tobacco mosaic virus and the actual virus encased in water ice, based on what I read.
It says it’ll be “cooled to the quantum ground state”. Isn’t that at/near absolute zero? Maybe the bacterium would be completely frozen…
A bacterium to replace a kitteh? Preposterous!
I’d far rather they did this to a bacterium than to a cat.
“How Can You Be In Two Places At Once When You’re Not Anywhere At All” Firesign Theatre 1969.
Will they be able to superpose Aluminium and Aluminum?
Bacteria have all the fun.
Sup. (as in superposition)
Of course it will trigger the Chopra Itch. [ https://en.wikipedia.org/wiki/Copra_itch ] The twitter nut was comic gold too.
Seems to me the experiment wants to use a glycine radical spin transition in the same way people have started to use diamond dopants as qubits [ https://www.eecs.mit.edu/news-events/media/englund-teams-enhance-duration-quantum-states-towards-practical-quantum-computing ] or sensitive probes of its immediate surrounding. (Here the environment would be a flash frozen bacteria cooled to near 0 K.)
Re the dangers of having a dead bacteria in “two places at once”, it is in Sean’s manyverse quantum theory that they are real bacteria (unless I am mistaken). In other theories observables are not necessarily real until they are observed. And even in MWT any interaction will make the alternate bacteria inaccessible from any specific universe.
Great. Now I have no excuse for not being at a meeting and at a different meeting at the same time.
No, no, no. You are looking at it wrong. You can be at a meeting and also be home in bed sleeping.
I more or less understand the aluminum film experiment (that means I more or less follow the math), but am a bit skeptical about the bacterium proposal. For one thing the aluminum film (made up of of identical Al atoms, BTW) is cooled to near absolute 0, so that everything is in the ground state. To claim that any experiment at this temperature is performed on a ‘living’ bacterium seems a bit of a stretch.
Maybe if they used a bacterial endospore?
Does this interact with the material basis for a lack of free will? I feel like it should but can’t put my finger on it. If superstition is real are both worlds equally real? Would the two ‘mes’ be the same me? Would both be bound by the same chemistry?
Gifford lectures – have they not a religious twang?
I’m no physicist, but wouldn’t the deocoherence time here be ridiculously small? (I think that’s the right question!)
Of course! All you have to do is to vibrate the foil at the same rate as our universe. Then you can use the harmonics to jump to other universes. Simple isn’t it? ’tis the musik of the spheres!
I guess my only question is what would be the implications if they succeed? If they mentioned this, I didn’t catch it.
It’s all geek to me.
It’s all part of an ongoing effort to expand the practical limits of superposition. Some formulations of quantum mechanics (e.g. Copenhagen) insist that at some point the superposition must collapse (exactly how and when isn’t specified) to produce a unique macro-scale outcome.
Other formulations (Everettian aka “Many Worlds”) see no need for this arbitrary collapse postulate, and maintain that there’s no reason in principle that the entire universe couldn’t be in a superposition of (non-interfering) states.
So the ability to demonstrate superposition at larger and larger size scales tends to cut the legs from under collapse formulations and lend support to no-collapse formulations.
That’s my amateur view of it anyway.
That helps Gregory, thanks!
It’s amazing how strongly that resembles English!
Yes, just like listening to Professor Stanley Unwin
Ha Ha Ha, exactly! 😀
In addition to what Gregory said, I think being able to put larger structures into decoherent states may have future practical implications for quantum computing. I imagine a lot of chip engineers would be relieved to know they don’t have to create 3-atom circuits in order to get the effect to work.
You’re all idiots for bothering with this topic. WHY DONT YOU STICK TO SOMETHING YOU KNOW??????
I’d like to apologize for the above comment. I didn’t write it, it was my Schrodinger Twin, and he knows my password ( of course) He also happens to be a real wus (unlike me)
There’s probably four of you by now. Or 2^x, where x is the number of times someone doesn’t understand anything he’s reading about the experiment.
There’s no such thing as a rigid cantilever. A very, very stiff one, yes. Perfectly rigid, no.
I know this is even farther beyond my pay grade than this is Jerry’s…but I still get the impression that we’re in a situation akin to where we were after we were certain that Mercury’s orbit wasn’t what Newton said it should be and before Einstein figured it out. Lots of people doing great research, looking for extra planets, trying to figure out just what was going on…and then a radical reformulation of our perspective and it suddenly made sense, in a sense…for those for whom Relativity makes sense….
I’ll bet a cup of coffee that we’ll eventually collect enough exciting new data from the LHC and NASA and all their friends that something will finally “click” for somebody, and then we’ll have a brand-new model that, of course, reduces to Quantum and Relativistic and Newtonian Mechanics at their respective scales, but as different from them as they are from each other.
That somebody will be somebody like Sean, or maybe like Sean in graduate school…but, statistically, we can be very confident that it’s not any particular individual you care to name, including Sean. But it’ll be somebody at least as immersed in and comfortable with the subject as Sean; that’s for certain. And it’ll be a generalist, like Sean, not a specialist…which is something of a problem, since the field is bordering on too much for anybody to generalize any more. Might have to wait a few more generations for the specialists to finish digesting it into a comprehensible whole.
…but, man! How exciting to live at a time when we’re actually in the thick of exploring all this and making these discoveries! And, with the Internet…it’s like Newton publishing his lab notes in the newspaper, only so much better!
b&
I think a case can be made that the click you’re looking for has already happened, albeit in several stages.
The first click was quantum mechanics itself, which suddenly made sense of a lot of questions that had stumped classical physicists. Early formulations of QM introduced some head-scratchers of their own, but most of those arguably evaporated in 1957 with Everett’s formulation, which basically says to take the math at face value, stop worrying about how to collapse everything down to a unique macroscopic history, and let the universe exist in a superposition of states just as the Schrödinger equation says it should.
What would that look like from the inside? Turns out it looks exactly like what we actually see. Click! Suddenly everything gets a lot simpler and makes a lot more sense, but it does entail a radical reformulation of our perspective on what constitutes reality — which is what you asked for.
A reading suggestion, writing of an Oxford physicist/philosopher, David Wallace, who in IMHO has made that “many-worlds interpretation” much easier to ‘swallow’. Firstly, you can easily find an approx. 2011 guest post by him on Sean Carroll’s blog. If you like the writing and can get hold of it, his 2012 book entitled “The Emergent Universe” is very hard going for most of us in its 500-page entirety. Despite the title, it is not a ‘mere’ science popularization, quite the opposite. But the writing is particularly clear, and many pages near the beginning of a few chapters are quite digestible without any huge math/physics background.
I cannot resist quoting the 2nd and 3rd sentences of his Ch. 1, to illustrate that entertaining writing, this bit being clearly a ‘challenge’ to the ‘shut-up-and-calculate/Copenhageners’:
“…There is no mystery at all about what the claims of our best theory of dinosaurs are supposed to be: they are supposed to be about dinosaurs, they are supposed, quite literally to be telling us about the giant animals we believe lived on earth tens of millions of years ago. Nobody seriously believes that ‘dinosaurs’ are just a calculational device intended to tell us about fossils; everyone knows that the purpose of palaeontology is to make certain factual claims about certain aspects of the world (in this case,aspects in the past)…”
Sorry, should have been “The Emergent Multiverse”.
http://blogs.discovermagazine.com/cosmicvariance/2011/11/18/guest-post-david-wallace-on-the-physicality-of-the-quantum-state/
b&
Hmmm…you might have a point.
I’m still expecting something different, maybe even different yet again, after the dust settles when gravity gets fully reconciled and we’ve got a solid theory of cosmogenesis.
Different how? If I knew, I’d have my Nobel….
b&
Maybe someone should scout the Swiss patent offices for fresh talent?
Have you patented that idea?
I have no insight into this topic, but it sure is nice to read the comments from the physics-minded.
I did recently read: “Quantum ‘spookiness’ passes toughest test yet.”
At: http://www.nature.com/news/quantum-spookiness-passes-toughest-test-yet-1.18255?WT.mc_id=TWT_NatureNews
The only insight I was able to glean was that the “hidden variables” of physics sound like confounders to my epidemiology-trained head. But, I heard from Thomas Lumley (statistician) that my understanding was roughly how Einstein was viewing the issue but precisely what Bell’s inequality says is impossible. “Latent common causes can’t get the right correlations” (Lumley).
I’m guessing there is some (indirect) connection to the present topic of quantum superposition and Bell’s inequality?
Clueless but curious 🙂
Only if the hidden variables are *local* in the technical sense.
Not believing this until I see an endorsement by Sean Carroll (the phycisist).
Schrodinger, in his proposal of the dead and alive feline thought experiment, was attempting to point out the absurdities of the current quantum theory. He’d probably do the same today.
After reading that ,I think I’m in a Superpositive State.lol
Its feasible, perhaps this is *really* how life spreads throughout the Universe.
Planet supercools after its parent star goes dark and eventually regions of the surface approach absolute zero resulting in dormant organisms tunneling (with a non zero probability) to other planets potentially thousands of light years away.
If we encounter aliens one day it is quite likely therefore that they will contain DNA, RNA and similar nucleotides as a result.