Gravity Wave Detection Using Entanglement?
Clifford at 11:58 am, May 25th, 2006Despite the annoying use of the words “spooky” and “weird” (why do people so often use those words when talking about quantum mechanics? why? why? why? why?!), I’d like to point you to a nice New Scientist article about the possible use of quantum entanglement to detect gravitational waves. It is by Zeeya Merali, and you can find it at this link.
Have a look and come back and tell us what you think, and/or ask questions. We’ve experts in both areas as readers who might also comment, and who might respond to others’ thoughts on the matter.
-cvj
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This is a neat idea, but would it be any less susceptible to the background noise that occupies current efforts like LIGO? Why or why not?
Would this detect gravitational waves from temporally stable objects or from a catastrophic event (supernova) or some other one time phenomenon?
I’m skeptical, and the one paragraph explanation (quant-ph/0605135) of entanglement swapping wasn’t clear to me. The strains being measured in LIGO are really small, 10^{-21}…and I’m not sure how this improves on that problem.
On a somewhat related note of connecting gravity with tabletop experiments, consider measuring the value of g. BEC’s can measure g and possibly act as gravitometers, which is kind of exciting…see http://massey.dur.ac.uk/articles/newoptics.pdf
Quantum Mechanics *IS* spooky
Haven’t read the link yet, but I just had to throw that in.
Of course, GR is pretty spooky too. But QM… man, that stuff is spooky.
Max Tegmark gave a public talk where he made an excellent point: why should we *expect* the fundamental laws of reality to work in a way that is intuitive to our brains? Our brains (particularly our conscious minds) evolved to deal with spatial scales of millimeters to kilometers (if even that), and timescales of a tenth of a second (generously) to years. We have mental models that work well on those scales… but have never been optimized on anything else. That’s not really much of a range of space and time scales there. On the must fundamental levels– small spatial scales, small timescales– things may be different from what we’d expect with a good functional model from “human normal” scales. Likewise for really big scales And, sure enough, they are.
The world just doesn’t work the way we think it ought to, unless we’ve studied enough relativity and quantum mechanics to understand something about the way the world really works.
-Rob
I also think that QM is weird and spooky. It’s not the main attraction, but it doesn’t hurt.
Ways in which we look at gravitatonal fields are interesting to me. Are these appropriate?
Maybe Rob, like seeing the interferometer from it’s early inception(Michelson-Morley experiment) to how it is used today?
How does the photon act in a gravitational field?
Atomic Fountains
And of course, what use atomic clocks in terms of resonance curve?
Adam, Rob Knop:
“Weird” and “spooky” imply -to the outsider- that there is something central that is not understood about how Quantum Mechanics works, when in fact we can compute results with it to remarkable accuracy. (Notice that I did not use the word “why” in the previous sentence, but “how”.) Using those words therefore undermines a popular level article a little bit … the outside reader reads it and thinks “well, if they don’t understand how QM works, how are they going to reliably apply it to do something?”. Anything then concluded with the use of this “spooky” or “weird” thing is suspect in that reader’s mind. I think that the word you - as people who understand QM - are thinking of is “counterintuitive”. This is not the same as “weird” or “spooky”, imho.
So I repeat. It is not “weird” and “spooky”, it is “counterintuitive”. The latter does not mean that we cannot work with it with 100% reliability…. the former two words suggest that we cannot, at least to the untrained ear.
-cvj
Quantum Mechanics? That’s normal by now. Gauge invariance, now that is some spooky stuff.
See how this works? We just start calling the next thing spooky or wierd and then it gets posted to the front page of digg. And, for this, everyone is that much wiser.
Uhhhh sorry to be unhip and all, but what is digg?
Whoa! You mean this? http://digg.com/
>shakes head slowly < …learn something new everyday…..
-cvj
I don’t take ‘weird’ or ’spooky’ to mean ‘not well understood’. Yes, to me, it really does mean something like ‘counterintuitive’, but I’ve not got the impression in my time teaching or talking to laypeople, about QM, that most of them take the use of those words to mean ‘not well-understood’.
As for being well-understood*, that’s true for pure states; mixed-state entanglement/specifying LOCC operations, for example, has a ways to go (and mixed states are the most interesting ones, practically).
*By ‘well-understood’, I’m really talking about ‘we can make predictions with accuracy’; I think that’s all physics can claim to achieve, in fact.
How important is it to understand the nature of the photon, in all the research going on? Glast, in gamma ray detection?
Will this information help in understanding the entanglement issue, from the “wording of Plectics” by Gellman” that I had mentioned previously, and on name.
Teleportation breakthrough made, By Paul Rincon
It relies on a strange behaviour that exists at the atomic scale known as “entanglement”, whereby two particles can have related properties even when they are far apart. Einstein called it a “spooky action”.
Scratching head….. and Penrose called for a new spacetime/quantum world view by defining it as quanglement?
I remember reading an earlier paper making a similar suggestion. I have no idea what the feasibility is, but I would guess that it’s not comparable to LIGO, or else everyone would be doing these instead.
I will remark that quantum superpositioning is nearly as spooky as quantum entanglement. Therefore, I will pose an extremely naive question: If gravity waves can imprint their signature upon entangled particles, then is it quite plausible that gravity waves can imprint their signature upon particles in superposition? Just a simple reminder… The annoying term “spooky” continue to endure in popular culture because this term is a direct descendant of a phrase coined by Einstein: spooky action-at-a-distance.
I’ve been pondering something that your comment brought to mind… where do we draw the line between description and explanation?
Most people see Schroedinger’s equation and think wow, these particles are teleporting, etc…. but being a very good description of what we observe and painting a physical picture of events are two different things. I’m not saying that it’s wrong, but I think the next big leap will come from an emphasis on rigor and a resulting focus on examining our picture of what is happening, followed by changing that picture, rather than fitting more math into its framework.
Or maybe I’m talking out my ass. What do you think?
I always preferred Einsteins “Quantum Mechanics: Real Black Magic Calculus” over his “spooky”.
Of course when Einstein said spooky he actually did mean ill-understood. And one can reasonably claim that it is.
Superposition is the root of spookiness.
adam: With regards to your above comment #16, are you implying that quantum entanglement is simply an offshoot of quantum superpositioning? I view entanglement and superpositioning as two distinct concepts with some overlapping features. In general, I thought superpositioning refers to the operations of a single subatomic particle. In contrast, entanglement refers to the operations of two or more subatomic particles.
Hi,
somewhat off-topic and smart-aleck like: Working in the field of gravitational physics, I’d like to point out that it might be better not to use the term “gravity waves” in the context of gravitational radiation. Researchers in my field tend to use “gravitational waves”. The distinction is important, since the term gravity waves is primarily used in fluid dynamics to describe fluid oscillations that have gravity as their restoring force (link to Wikipedia).
In fact, quadrupole (and higher-l/m order) gravity waves in protoneutron stars may be strong emitters of gravitational waves!
Christian: Your point is well taken… However, because ‘New Scientist’ has placed “gravity waves” in the title of their feature article, you probably ought to also direct your complaint to the editor of ‘New Scientist’. As far as my usage of the term “gravity,” I was using the phrase “gravity waves” over “gravitational waves” simply because “gravity” requires less text than “gravitational.”
Doh! I share Christian’s bias, and I’m not even in that field.
“Gravity waves” are ocean waves, and are probably the kind of waves that most people are most familiar with.
But, if the common nomenclature changes… well, I guess we have to live with it. Unfortunately, there will be much confusion as old textbooks and people who know the real definition of gravity waves collide with people who’ve read “gravity waves” as what LISA is going to look for.
-Rob
Hi Clifford —-
Since I allegedly know something about gravitational waves, thought I’d take a look at this. My conclusion is very similar to Seth Lloyd’s — it’s a neat concept, but I have a hard taking this seriously as something that would be pursued anytime in the near (or even not-so-near) future.
The basic idea is that entanglement correlates the momentum and spin states of widely separated “test masses” (in this case, particles that respond to the passing GW). Hence, by monitoring spin states, you infer something about the momentum of the distant particles. Thinking of the GW as acting like a force (not something a GR purist would do, but a useful paradigm for exercises like this), you thus can in principle infer the action of a GW.
What’s missing from the paper is any discussion of practical issues. In particular, how can we tell a GW from noise? What makes something like LIGO feasible is that the GW signals are frequency bounded (so you can filter out noisy bands and focus on those of particular astrophysical interest), and spatially coherent with a particular angular distribution. Noise is incoherent and typically stochastic. One tries to take advantage of the coherency of the signal vs the incoherency of the noise to overcome the inherent weakness of the signal being searched for.
Where I can imagine this entanglement idea paying off is that you are essentially making the GW detector into a coherent quantum state. Thus, you presumably gain in sensitivity in proportion to N, the number of particles used in the detector. By contrast, a “classical” detector typically gains in sensitivity in proportion to sqrt(N) for appropriate definitions of N. (For example, the sensitivity in a laser interferometer at high frequencies is set by the number of photons gathered over a measurement, and goes with the square root of that number.)
My guess is you’d need an enormous N to overcome the inherent weakness of astrophysical GWs. The authors of this paper talk about an amplification procedure that could compensate for this weakness. Still, there’s a hell of a long way to go. The number of states that would need to be entangled to be sure of beating noise is probably pretty far beyond what is feasible anytime soon. Maybe when quantum computation is routine, this could be the next challenge for people interested in quantum measurement.
cheers,
scott h.
ps — the nomenclature issue (”gravity waves” vs “gravitational waves”) is really annoying, particularly when (as Christian notes) you are looking at a situation in which gravitational waves and gravity waves, with their separate proper meanings, both make an appearance. In my papers, I typically write “gravitational waves (GWs)” once, and then use GW and GWs from then on.
Cynthia 17: my point was that without superposition, there’s no entanglement.
In terms of “gravitational waves” and “gravity waves,” some points to remember.
Thanks
Scott H., and others. Thanks! I (and probably others) learned a lot from your comments on this.
-cvj
Rob Knop on May 25th, 2006 at 7:03 pm
Interesting picture in your hands. What is it? Is it the picture in linked quote?
The superposition, entanglement paradox?
Take an item in an entangled state as the only thing in existence (Universe with a two-particle content), then the only information you can learn about the entangled state, is the gravitational attraction of the two particle system?
Basically, if there were a system that was in so much isolation from anything/everything else (thats what must be attained, noise from anything will cause so much pollution) in the Universe, then GW’s would be “strong” in signal terms.
Making matter exist in a “PURE-STATE” is simply what must be achieved, any particle that is entangled, MUST be shielded from everything that could influence or collapse the state into a “non-entangled” system. The whole basis of Entanglement and superposition is that if one creates a “table-top” experiment, that is entanglement, then the two particle state is, whilst it exists, classed as the only things in existence, as far as those particles are concerned , nothing else in the “UNIVERSE” Exists?
Just how one sets up the detector to gleen information, without disturbing the pure state, is akin to the early universe, the detector MUST recieve information of the system, BEFORE the system recieves information of the detecter?
Well, maybe develope a place, where such a beginning is understood? Create some association in ICCUBE and secondary particle recognitions? Of course they need a wide array of detectors?
If LHC can monitor in the calorimeter, then why not in how we percieve the “early universe” contained to events?
If, supersymmetrical relaizations from such a collapse created then what issues forth in terms of entanglement?
“Plectics” in this case, recognizes the very beginning?
Plato Yes indeed!
The aspect of detector/detection is parmount. I have an idea about the creation of a delayed “detector”, one that can infact be tuned to a “one-way” mode?
Again, one has to detect, before one is detected?
What effect of Moore’s law, while we think the “varying energy” of gamma ray detection, allows us a view of the cosmo much deeper then we ever had before? The “distant past” here now.
Our Window on the Universe. Can it then be distorted?
Paul Valletta - if you are still making contact with this thread…
Perhaps there is a solution to the underlying “chicken and egg” problem in regards to the origins of entanglement and superpositioning… If one assumes the “tightly-bound, Pre-Bang” condition as having pure-state entanglement, then superpositioning can be viewed as an emergent feature of the expanding cosmos. Therefore, as the universe evolves with expansion, superpositioning “kicks-in” to create mixed-state entanglement.
Intersting article! Some time ago I read an article about the possibility of using light from stars to detect gravitational waves:
Detection of gravity waves by phase modulation of the light from a distant star
Cynthia:
http://en.wikipedia.org/wiki/Spin-statistics_theorem
can be elaborated further?
All things having “already” been washed by GW’s, and thus fixed by expansion. Contraction of say a Bose-Nova(squeezed state), will reveal interesting properties regarding the GW’s signals.
Finite measure is achievable via local “Quantum TO Macro” paramiters, not “Macro to Quantum” !
Missed another link:http://en.wikipedia.org/wiki/Degenerate_star
Which ties in neatly with the Count’s Post!
If your dealing with a 5d world there are certain assmptions you make? Even from a supersymmetrical point of view, it is tied together microscopically as well as macroscopically?
Clifford:
What about the measurement problem? What is not understood is how to deal with quantum mechanical observers. The way QM is formulated rules out non-classical observers and is thus incomplete. Although one can argue that observers need to be large, you can in principle make intelligent quantum computers.
In Kaku’s preface of Hyperspace, page ix, we find a innocent enough statement that helps us orientate a view that previous to all understanding, is counched in the work of Kaluza.
In para 3, he writes,
Strominger:
Two papers that give clue’s:
http://arxiv.org/abs/physics/0111058
is the first step, and this:
http://arxiv.org/abs/physics/0605227
is the authors latest paper.
“Making matter exist in a “PURE-STATE†is simply what must be achieved, any particle that is entangled, MUST be shielded from everything that could influence or collapse the state into a “non-entangled†system. The whole basis of Entanglement and superposition is that if one creates a “table-top†experiment, that is entanglement, then the two particle state is, whilst it exists, classed as the only things in existence, as far as those particles are concerned , nothing else in the “UNIVERSE†Exists?”
Thus, that includes any DETECTOR/OBSERVER!