Entanglement Makes Quantum Particles Measurably Heavier, Says Quantum Theorist

KentuckyFC writes: Physicists have long hoped to unify the two great theories of the 20th century: general relativity and quantum mechanics. And yet a workable theory of quantum gravity is as far away as ever. Now one theorist has discovered that the uniquely quantum property of entanglement does indeed influence a gravitational field and this could pave the way for the first experimental observation of a quantum gravity phenomenon. The discovery is based on the long-known quantum phenomenon in which a single particle can be in two places at the same time. These locations then become entangled — in other words they share the same quantum existence. While formulating this phenomenon within the framework of general relativity, the physicist showed that if the entanglement is tuned in a precise way, it should influence the local gravitational field. In other words, the particle should seem heavier. The effect for a single electron-sized particle is tiny — about one part in 10^37. But it may be possible to magnify the effect using heavier particles, ultrarelativistic particles or even several particles that are already entangled.

Comments

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Re:GNAA has GAY NIGGER ENTANGLEMENTS AVAILABLE NOW

[Anonymous Coward]

You may want to look into getting MyCleanPC.

Uh No

[Anonymous Coward]

We can't measure anything using any instrument anywhere to a precision of 1/10^37th. Bullshit meter is off the charts

Re:Uh No

[bobbied]

Sure we can.... Light years....

Re:Uh No

[disambiguated]

No, really. We cannot measure anything to 37 decimal places. Not even close. If you measure the speed of light there will be uncertainty. If you insist the speed of light is exact by definition, then the uncertainty is in the length of a meter or the duration of a second or both.

Re:Uh No

[Anonymous Coward]

I can measure any damn thing I want to 37 decimal places. The trick is starting with a unit that's sufficiently large, like 1 universe. Now, your unit describes fractions of it. Seeing as there's at least 1.45x10^53 atoms of ordinary mass, I think 37 decimal places will work.

Measurement error is yet another number, which is given in conjunction with the measured value. Given our hypothetical universe unit, I think the measurement error can be safely hidden past 37 decimal places.

Re:Uh No

[sribe]

Sure we can.... Light years....

No, we can't. Think about it for a second ;-)

Re:Uh No

[Tough Love]

The size of the visible universe is only on the order of 10^9 light years, so that won't do it. But combine it with the range of the weak force, which has been measured and our direct measurement capability spans a range of about 10^39 (weak force ~= 10^-18 meters, lightyear ~= 10^12 meters, visible universe ~= 10^9 lightyears) so we can at least comprehend this number in a concrete way. Measuring it even indirectly... not going to happen with your basic bathroom scale. But we are talking about finding a way to relate effects on the Planck scale to the cosmogical scale so big exponents should be unsurprising. Unlike the outspoken AC above I will wait for peer review before adjusting my bullshit meter. Naturally, we all want to believe there is some big breakthrough here after the endless low calorie diet of contrived mathematical attempts to unify the big theories for the last too many decades. Is this one it? Seems unlikely just based on the long run of failed attempts. But I will just sit back with popcorn and enjoy the show. At worst, a refreshing break from the usual multidimensional mathematical salad parade. I'm particularly interested in more eplanation of how two entangled particles became one, at least according to the press.

Re:Uh No

[Okian Warrior]

We can't measure anything using any instrument anywhere to a precision of 1/10^37th. Bullshit meter is off the charts

We can't make any single measurement which contains 37 digits and have each of those digits accurate, that's true.

Just out of curiosity, how do radios work? I'm told that the measurement units for an antenna nanovolts per meter. Does the receiver make a 12-volt measurement to 8 digits of accuracy in order to recover the signal?

Or does the receiver amplify the signal so that it's large enough to be readily detected?

And is there no way to make multiple measurements so that the effect adds up? Can we do a million measurements added together to make the signal a million times stronger?

Re:Uh No

[Anonymous Coward]

Yes, you can measure anything to any number of digits. After the last significant digit you can just start making them up. Because when someone is talking about how many digits they measure to, they are talking about significant digits. Yes, it's a short hand, but a well understood one.

Re:Uh No

[Anonymous Coward]

Minor error in googling. There's probably closer to 7.4x10^79 atoms at a minimum (extrapolated from the initial #, which is visible mass, taken to be hydrogen, then multiplied by .74 to get just the hypothetical hydrogen atoms).

This only shores up my point that 37 decimal places is not all that astounding given the proper units. Context matters. A blanket statement that "we cannot measure to 37 decimal places" is as useless as a measurement with no figure for error and no units given.

Re:Uh No

[Anonymous Coward]

Only one of the meter or the second can be independently uncertain. The speed of light in a vaccuum, whatever it is, is exact and therefore we say it exactly relates 299972458 meters to one second, with the smallest uncertainty originating from the measurement of time's passage.

The uncertainty limits are set by resonance bandwidths of the transitions measured by atomic clocks (There is no "time-energy" uncertainty relation, because time is not an operator that can fail to commute). Cesium has been pushed down to a relative uncertainty of 10^-14sec/sec; Because the frequency is so much higher, aluminum ion clocks can acheive uncertainties around of 10^-17.

However this only applies to direct measurement: A cesium clock's output frequency is stable enough that the GR-induced change in frequency due to raising it one meter higher, for example, is directly measurable because that change is larger than the random wander. But if you know what you're looking for, there are other techniques to extract a signal from far below the noise floor (c.f. lockin amplifier / synchronous demodulator) or ways to derive side-effects which provide a better SNR in the first place (e.g. a Higgs itself will never be directly observed, but the LHC picks up plenty double-photon or 4-lepton events)

Re:Uh No

[Man On Pink Corner]

Your question doesn't have a simple answer, but if it did, it would involve signal-to-noise ratio within a given bandwidth. A radio receiver with a bandwidth in the audio range (~10 kHz) can amplify a signal by about ten trillion times its original power or a few million times its original voltage, before hitting the thermal noise floor of -174 dBm/Hz. These figures aren't exact (for one thing, they neglect the impedance change from a 50-ohm antenna input to an 8-ohm speaker) but the basic idea is correct: the noise floor at 25C in a 50-ohm system is -174 dBm/Hz + 10*log(bandwidth) dBm.

You can improve SNR by making your measurement near absolute zero, but you can't get rid of the noise entirely because some of it isn't strictly thermal in nature. Synchronous demodulation can let you recover information from below the noise floor, given a carrier of known phase. There are other tricks and hacks, but the bottom line is that you are still going to be at least ten or fifteen orders of magnitude away from being able to work with 37 significant figures in any real-world physical measurement. Integration times for such a measurement would have to approach heat-death-of-the-Universe durations.

Re:Uh No

[Anonymous Coward]

Good thing there was a whole second half of the sentence addressing that...

Re:Uh No

[disambiguated]

Only one of the meter or the second can be independently uncertain.

Yes you're right I was thinking of mass (or force). In any case, the choice of which units to define and which to measure is arbitrary, so it makes sense to define the ones we have the least ability to measure.

Cesium has been pushed down to a relative uncertainty of 10^-14sec/sec

Which is a mind-blowing achievement, I think, but it's still a far cry from 10^-37.

However this only applies to direct measurement: A cesium clock's output frequency is stable enough that the GR-induced change in frequency due to raising it one meter higher, for example, is directly measurable because that change is larger than the random wander.

That's also amazing, and maybe there's a way to test this "entanglement makes particles heavier" idea, but we still aren't going to get measurements of anything down to 10^-37 that way. You mentioned "one meter higher", so that can't be better than our measurement of the meter (or second), right? I'm not a physicist. :)

Re:Uh No

[Anonymous Coward]

Turns out it makes no difference whatsoever what units you use. We don't have the ability to measure anything to 37 decimal places in any units. 7.4x10^79 atoms is two decimal places.

Re:Uh No

[Beck_Neard]

Radio receivers work through several mechanisms. First, you have an antenna that is only sensitive to a certain frequency range (but highly sensitive in that range). Then you have some kind of tunable resonant circuit that narrows down the range of frequencies even further, ideally to just the single frequency band you're looking for. When radio reception is good, the signal/noise ratio in that band is quite large, even if the signal is weak. That is, the radio signal is overwhelmingly the most powerful thing in that band, far more powerful than the noise in that band. So it's not really a measurement of '8 digits of accuracy'. It's more like 3 or 4 digits of accuracy.

Re:Uh No

[l0n3s0m3phr34k]

No, at worst is these experiments to prove this cause the Earth to collapse to the size of a pea.

Re:Uh No

[StripedCow]

"decimal places" should have been "significant digits".

Turns out the parent post was only accurate to within its first 44 characters.

medium disclaimer

[Anonymous Coward]

please add a disclaimer that the content is served using medium.

Re:medium disclaimer

[Fwipp]

You can't hover over links before you click them?

Re:medium disclaimer

[Anonymous Coward]

Am I supposed to know why this is apparently a bad thing?

Re:medium disclaimer

[Anonymous Coward]

I think he wants the disclaimer in the headline so he can ignore any article based on a link from that website.

Re:medium disclaimer

[Anonymous Coward]

medium is the goatse of words.

Re:medium disclaimer

[Anonymous Coward]

You can't hover over links before you click them?

He must be using a current Firefox or Chrome browser.

I guess the "good" news is the next major IE version is to copy the Firefox GUI, so it too will no longer have a status bar or show link targets. Then we can all be equal and finally get along.

Re:medium disclaimer

[Anonymous Coward]

Current Firefox and Chrome both show link URLs on mouseover.

Particle physics is easy ...

[Cassini2]

We only need to measure the mass of a 9.10938291 × 10^-31 kilogram particle accurate to 1 part in 10^-37. Alternatively, we can speed the electron up to 0.999c so it weighs more, then entangle it, and then measure it's mass to 1 part in 10^-37, with less than 5 sigma of measurement error.

Either way, I should have it done by lunch time.

Re:Particle physics is easy ...

[Anonymous Coward]

You've got 8 decimal places already. Only 29 to go! You are well on your way, especially since you posted late afternoon. You have about 19 hours until lunch. Come to think of it, I think I have a scale that measures kilograms +/- 10^-68 kilogram.

This really is non-news. The whole reason the theories of gravity and quantum mechanics work so well is that they never have to play in the same measurement. They are around 30 or 40 orders of magnitude different. And seriously, only Capt. Dumass could think you could get 37 or more significant digits in a measurement. Really? You can measure the meter bar to within one one hundredth of a Plank length? You could measure a distance of about a light year to within 1 trillionth of a nanometer? Ok. Seems legit. I can't see any technical hurdles.

Re:Particle physics is easy ...

[radtea]

Either way, I should have it done by lunch time.

Or we could spend some time coming up with additional consequences that might allow indirect tests. For example, does this effect have any consequences for the spectrum of Hawking radiation (just to consider one area were entangled pairs and high gravitational fields are involved)?

How about the structure of the very early universe?

Or are there ridiculously subtle interferometric effects that might allow the detection of the phenomenon? Or other quantum effects?

Consider the Mossbauer Effect as an example of measuring stupidly small energy splittings so many orders of magnitude below any reasonable detector resolution that no doubt some smug bastard made fun of the people doing the hard work of calculating them "because no one will ever be able to measure that!"

Re:Particle physics is easy ...

[smaddox]

Mod parent up.

Also, perhaps further development of the theory could hint at methods of unification of QM with GR.

Re:Particle physics is easy ...

[rgbatduke]

You saved me from having to reply. I do not think that this "measurably heavier" means what you think it means (or rather, they think that it means), to quote Inigo Montoya. Let me 'splain. No, there is too much, let me sum up. In addition to the fact (as you have so ably pointed out) that we will never, in the future course of the universe, be able to measure the effect predicted, it is a theoretical prediction based on assumptions in a particular circumstance. If the assumptions turn out not to be correct, it might not be any more correct than the assumptions. And since we will never, ever, ever be able to verify the prediction of measurable changes in weight -- where I am pretty certain that they meant to say "mass" and not "weight", since the former is an intrinsic property of particle configurations and the latter describes the macroscopic Newtonian force between two objects where traditionally at least one of the two is rather large, say a planet or a star -- of two quantum entangled microscopic particles in a Universe where the other forces acting on them are tens of orders of magnitude larger under pretty much all circumstances, we cannot even use this to demonstrate the empirical consistency of the unproven theory.

I'll have it done by lunch time, as long as the lunch is held in the restaurant at the end of the Universe, which I will get to via an infinite improbability drive using the plausibility of measuring the difference in weight of quantum entangled states.

Oh, one last thing. Everything is in a quantum entangled state. Literally everything. All of the time. After all, there is no "outside" of everything to perform a classical measurement and force the system to disentangle. Something to think about, while contemplating the Nakajima-Zwanzig equation -- for the Universe:

http://en.wikipedia.org/wiki/N...

rgb

Re:Particle physics is easy ...

[rgbatduke]

Sure, and consider that we do not yet have direct experimental confirmation that antiparticles fall down, instead of up. There's a reason for that, and it is 30 orders of magnitude.

The antiparticle experiment actually might be doable. And it is the thing that is a mere 37 orders of magnitude short of measuring the difference in weight of entangled quantum antiparticles.

So yes, you are right, one cannot be certain that there is no supremely clever way to measure Planck-length scale phenomena without using experimental probes with the energy of a freight train per particle and so on. What we can say with certainty is that at this particular moment, there is no justification for the use of any "measurable" variation of weight. No, there is no measurable variation of weight in particular, and probably no measureable variation of mass. The same laws of quantum mechanics that produce the supposed entanglement make it impossible to measure things at that resolution on a particle scale.

Now, if you could entangle whole planets, or even entire cats, matters might be different. I'd suggest building a scale and put Schrodinger's diabolical apparatus (plus a volunteer cat) onto it. Tell us what you measure regarding the difference in weight of the entangled vs non-entangled cat, bearing in mind that measuring weight is measuring so don't be surprised if the cat's state is collapsed to the classical one of live or dead but not both while you perform the measurement.

rgb

Re:Particle physics is easy ...

[l0n3s0m3phr34k]

I'll raise you this quote: "You'd like to think that, wouldn't you?!" yet on the actual arXiv site they do indeed say "Our results suggest that there is a form of entanglement that has a weight." It's actually the third word of the paper. And here, weight IS the correct term, as it is the measurement of the pull of gravity on an object. That's the whole point of the paper...current theory is quantum entanglement doesn't interact with gravity but these guys say in certain instances this might be incorrect. " Our results suggest that there is a form of entanglement that has a weight, since it affects the gravitational field." IANAQP, so here is the PDF so others can read it too and comprehend it better than I.

Re:Particle physics is easy ...

[Anonymous Coward]

"But it may be possible "

LOL
so unusual for these articles to have a title sounding like its just being or been done, and then finish with a "but it may be possible" clause that is about a bazillion years down the line

Re:Particle physics is easy ...

[Neil Boekend]

The mass difference between an entangled cat and a non entangled cat is the mass of the tread it got entangled in.
see these images

Re:Particle physics is easy ...

[rgbatduke]

So you're/they're saying mass-energy in any form doesn't have a "weight"? Einstein was even wronger? Rearrangements at constant mass-energy can have different weight? At the Planck scale you can say pretty much anything you like and not have much chance of your words being falsified, and while I'm not a falsificationist and agree that a consistent hypothesis can have meaning even if it can't be verified or falsified, this falls into the same scientific category that magnetic monopoles do, only tens of orders of magnitude worse. At least in the case of monopoles, I can understand all sorts of observationally true sequellae -- like charge quantization -- and they should be easy enough to observe subject only to their Bayesian prevalence and looking in the right places with the right tools. It wouldn't surprise me in the least if magnetic monopoles are eventually observed, adding a really, really important building block to our incomplete TOE. But in the meantime, I accord them only a weak degree of belief because I cannot rule out from a near infinity of hypotheses human have not thought of -- yet -- alternative explanations of the same sequellae that don't involve monopoles and because it becomes increasingly difficult to explain why we haven't observed at least one monopole yet unless there is some truly enormous energy barrier or symmetry breaking that we do not understand.

So I think that there is a very reasonable chance that monopoles exist and that physics completes in that general direction and that we'll eventually be able to take that "chance" (far too weak to call a "true fact") and turn it into a probably true fact through observation. I think that there is almost no chance that the hypothesis that entanglement alters weight at what amounts to the Planck scale ever gets any experimental validation either way. In its own way, it is like hypothesizing that dynamics at that scale is all due to neurotic invisible fairies. Which is, of course, very nearly a perfect metaphor for quantum field theory anyway.

rgb

Re:Particle physics is easy ...

[l0n3s0m3phr34k]

Personally, I'm not saying anything. I was just clarifying per the article of arXiv...AND I couldn't help but use another Princess Bride quote.

Re:Particle physics is easy ...

[rgbatduke]

:-)

BTW, nice recursively demonstrative 1337 handle...;-)

rgb

... that explains my doctor's visit

[Anonymous Coward]

Doc said I'm gaining weight. Now I know that I am just entangled. I will cancel my diet.

Re:... that explains my doctor's visit

[Tough Love]

Now I know that I am just entangled.

Massively entangled.

It's true

[Gliscameria]

Yo mama's so fat her wave function collapses into multiple eigenstates.

Re:It's true

[Anonymous Coward]

I noticed how fat yo mamma is when I got entangled with her last night.

A little tiny scale.

[Anonymous Coward]

As anyone who has been to weight watchers knows, of course you can measure 10^-37. Different underwear. Poop before going. Disentangle yourself from the universe...

Next Big Thing

[sycodon]

So what is going to be the Next Big Thing?

What is the next Theory of Relativity waiting to be solved and what will be the game changing technology made possible by it?

Re:Next Big Thing

[Gravis Zero]

not to spoil it for you but it's time travel. i'll be making my announcement in 2044 and personally demonstrate that you can travel 5 minutes back in time. needless to say, i forgot to carry the one.

Re: Next Big Thing

[Anonymous Coward]

Time travelling works fine. To prove it, I will travel back to when this article was accepted on slashdot and be the first poster. Be warned, time travelling makes me cranky and homophobic.

The fuck do you mean "heavier"?

[Anonymous Coward]

An increase in rest mass? Added momentum/energy?

I wish I could find somewhere that talked about physics without dumbing it down to the point that there's no actual information. I've yet to see anything about entanglement that isn't pop science nonsense, and it leads me to see it in the same light Einstein did - horse shit.

Re:The fuck do you mean "heavier"?

[Anonymous Coward]

> I've yet to see anything about entanglement that isn't pop science nonsense, and it leads me to see it in the same light Einstein did - horse shit.

Probably because you haven't looked. There are a number of independent studies confirming this.

http://en.wikipedia.org/wiki/Q...

For example, if a pair of particles is generated in such a way that their total spin is known to be zero, and one particle is found to have clockwise spin on a certain axis, then the spin of the other particle, measured on the same axis, will be found to be counterclockwise. If you separate and modify one of the pair, the other will change without a correlating cause to reach the previous state of equilibrium (between the 2). Why does this matter? You can control properties of a particle without observing or operating on it directly. Do you want to know the spin and where the electron is at any given moment? Find where it is and look at it's spin partner.

Re:The fuck do you mean "heavier"?

[Tough Love]

Presumably you get your pop science entirely from tabloids dear anonymous coward because entanglement has been throroughly verified by experiment. Too bad Einstein didn't live to see the flaw in his EPR paradox explained (Bell inequality).

Re:The fuck do you mean "heavier"?

[Anonymous Coward]

I've yet to see anything about entanglement that isn't pop science nonsense, and it leads me to see it in the same light Einstein did - horse shit.

You see things as Einstein did because you're pretending your over sixty years in the past? If you fast-forward to the 1970s, you can find journal articles describing experimental verification of entanglement and Bell's inequality. Or if you just check the internet, you can find more non-pop-sci literature on the topic than probably humanly possible to read, everywhere from leading research to free class notes and textbooks. When I was an undergrad 10 years ago, entanglement was one of the experiments done in an upper level undergrad physics lab course and studied in more detail by undergrad summer research.

Re:The fuck do you mean "heavier"?

[tendrousbeastie]

How do you modify the spin of a particle without measuring it? (and how would you know the difference of whether you had measured it or not?)

Re:The fuck do you mean "heavier"?

[Anonymous Coward]

Interactions with magnetic fields or photons. Stuff like the Stern-Gerlack experiment, especially when you have a magnetic field perpendicular to a known or superposition of states, you will get modified spins that result in "unknown" states (i.e. superpositions) until a measurement is made.

Re:The fuck do you mean "heavier"?

[Anonymous Coward]

Do you want to know the spin and where the electron is at any given moment? Find where it is and look at it's spin partner.

Entanglement doesn't allow you to violate the uncertainty principle. Although it helps that the spin operator will commute with a component of the position operator...

Neutron interferometry?

[Anonymous Coward]

I thought experiments in neutron interferometry already established gravitation influence upon quantum mechanical observations...

Not "does indeed"

[harryjohnston]

That's a theoretical analysis, not an experimental measurement, and is likely to be particularly dubious since we don't have a working theory for quantized general relativity yet. Interesting, but the phrase "does indeed" in the summary is a significant overstatement.

Penrose gravitational wavefunction collapse

[Anonymous Coward]

This sounds a lot like Penrose's proposal for wavefunction collapse caused by gravitational disturbance caused by particles being in a superposition of two locations...

Re:Penrose gravitational wavefunction collapse

[Anonymous Coward]

Yes, it does make you wonder what they were actually measuring, and if by measuring it, they nullified the entanglement....

Interesting use of measurable

[Crashmarik]

Seeing as you are talking about a change in mass that is 34 orders of magnitude smaller than the Planck constant

h/2 > (delta MV)(Delta x)

(6.62606957 × 10-34 m2 kg / s)/2 > (Delta (M)*V)(Delta x)

delta M = 9.10938215kg×(10^-31)/ 10^37
or = 9.10938215kg×(10^-68)

We are looking at some pretty big uncertainty about where the particle is and how fast it's moving.

Should have searched first

[Crashmarik]

The current uncertainty of electron rest mass is

http://en.wikipedia.org/wiki/E...

The 2006 CODATA recommended value has a relative uncertainty of 4.2×1010

So all you need to do is add 27 orders of magnitude to the certainty of the electrons mass.

It's even easier

[Okian Warrior]

[...]Either way, I should have it done by lunch time.

I see you've read the article, so can you explain something for me?

I'm told that photons gain energy when falling into a black hole. Suppose you have two entangled photons and one goes off and gets captured by a black hole.

Based on the article, would there be any noticeable effect on the other entangled photon?

Re:It's even easier

[Anonymous Coward]

The way photons gain energy falling into a black hole is by getting blueshifted. The velocity remains constant (c, of course), but the photon's mass increases as the wavelength shrinks, so it gains both momentum and kinetic energy.

Re:It's even easier

[Garfong]

It's kinetic energy increases, but its mass stays constant (exactly 0), as does its total energy (since it loses gravitational potential energy as it gains kinetic energy).

Re: It's even easier

[TimMD909]

Wait... e=mc2. Since the photon has energy, it should also have mass as "m" cannot be zero if "e" is nonzero. That's all I was able to understand from a Susskind lecture on the Higgs field.

Re:It's even easier

[smaddox]

How do you define gravitational potential energy such that a massless particle has any?

Regardless, both this comment and the parent comment are ignoring the importance of reference frame. Relativity is not at all my specialty, but it's unclear to me how you should talk about a single photon in relativistic gravitational fields, since it's impossible to make any measurements on the photon without affecting it's energy.

Re: It's even easier

[rgbatduke]

Excuse me? E^2 = p^2c^2 + m^2c^4 is the correct statement (or to be pickier, the four vector P = E/c - \vec{P} has conserved length equal to mc). Photons have zero mass, so for them E^2 = p^2c^2. You are thinking of E = \gamma m_0 c^2, which works fine for massive particles where m_0 \ne 0, not so well for light where \gamma = \infty because light travels at the speed of light.

BTW, does /. grok latex if one wraps it, that is, does $$E = \gamma m_0 c^2$$ work? Might as well try it...

No, apparently not. I suppose I'll have to look at actual documentation to see if there is any way to make it work.

Hey /. Dudes! You keep changing the site, improving it and so on! A 21st century website that cannot speak latex is so, not-even-20th century, and when that site is devoted to technology, it is vaguely insulting. Even wordpress can often understand $latex E = \gamma m_0 c^2$.

rgb

FTL communications?

[Ken_g6]

Given that two particles can emitted by a single source entangled, sent a long distance apart, and remain entangled,
And that if one particle becomes disentangled the other particle instantaneously becomes disentangled,
If we can measure the entanglement of a particle by its mass,
Then we can communicate faster than light.

But the no-communication theorem states that, during measurement of an entangled quantum state, it is not possible for one observer, by making a measurement of a subsystem of the total state, to communicate information to another observer.

So I think this means that either the no-communication theorem is wrong, or the change in mass of an entangled particle cannot be measured.

Re:FTL communications?

[radtea]

So I think this means that either the no-communication theorem is wrong, or the change in mass of an entangled particle cannot be measured.

That's an interesting point, but on my reading of the paper (which was pretty cursory, admittedly) the extra mass term comes from the joint wavefunction, which means both particles would have to be measured. It looks like the pair has greater mass, not the individual particles.

This makes sense because insofar as they are entangled it doesn't even make sense to talk about the individual particles. Furthermore, if one were to measure either of the particles individually, that would break the entanglement and the extra mass term would fall to zero.

Thing of the highly idealized experiment of two sources on a balance beam, one that emits pairs of non-entangled particles, one that emits pairs of entangled particles. The theory says that the balance will tip toward the side of the entangled pairs, but it does not follow from this that measurements on any of the individual particles will reveal increased mass.

Re: FTL communications?

[Anonymous Coward]

The entangled particles do not carry information because you don't get to choose what state the local particle collapses to. In the case of a hypothetical extra mass when entangled, you would have no way of measuring that mass without looking at the total system. So I don't think there's any contradiction.

Re:FTL communications?

[TheDarkMaster]

Sorry but the no-communication theorem seems BS. If you are able to obtain the polarization of the photon and you are also able to force this photon in a given polarization, and the photon is in an entangled state (existing in two places at once), so I do not see what would prevent the transmission of information using this effect and the theorem fails to explain what would be a good reason for this communication be impossible.

Re:FTL communications?

[Anonymous Coward]

You can't use entanglement to tramsmit information. By "obtaining" the polarization you also "force" it, this is the same process. This is quantum mechanics: measuring something affects the result. What you do is you force the particle to a particular state, and if it worked you "obtained" the state, otherwise it was the other state.

If you think about this, you'll see you can't transmit information, you can transmit a message, but only if you already agreed beforehand what the message was.

Re:FTL communications?

[TheDarkMaster]

Well, the idea is transmitting a message. If I understand correctly what you wrote, then the problem is that scientists do not have a method to assign a specific polarization to the entangled photon, I am correct? And if they can "read" the photon but still can not "write" on it, but someone finds the method of "writing" without interrupting the entlangment, then sending messages would be possible right?

Re:FTL communications?

[Anonymous Coward]

you are also able to force this photon in a given polarization

You can't. The entanglement is a particular polarization state of the system, and if you force a polarization on one end, it will no longer be in the entangled state, and there will be no impact on the far end. There are various things you can do to change the state of the system without breaking the entanglement, but mathematically none of them will give a particular polarization on the opposite end (without some classical communication involved), and both ends will always see what appears to be a random measurement result, that only happens to be correlated after they know what the other end gets. E.g. if you measure up-down polarization on such a polarization entanglement, your measurements will all appear 50-50 chances of up and down no matter what the other end does. It is more like a shared coin flip, with no way to force the coin to land a particular way.

Re:FTL communications?

[Anonymous Coward]

but someone finds the method of "writing" without interrupting the entlangment,

The existence of the entanglement is inherently the same thing your trying to overwrite. Writing a specific state to it is mutually exclusive with retaining the entanglement, and is quite basic to demonstrate with math in quantum mechanics. In other words, if someone finds a way to do so, quantum mechanics would be wrong on a very fundamental level and not just some trick of applying principles of quantum mechanics in a novel way.

Re:FTL communications?

[Anonymous Coward]

The existence of the entanglement is inherently the same thing your trying to overwrite.

Yes, that is the wrong "your" and should be "you're"...

Does this lend credence to Penrose interpretation?

[Anonymous Coward]

http://en.wikipedia.org/wiki/Penrose_interpretation

that should read 10exp10 not 1010

[Crashmarik]

What is with slashdot and the exponentiation symbol\

Maybe It's Me

[JimSadler]

It seems to me that one way to state this information is that mass can be a variable according to circumstances. And that screws the pooch. Are we entering an era in which every term in an equation is a variable? Can mathematics tolerate multiple variables within an equation? And if so to what degree can variables be the elememts of an equation and yield any useful solutions?

wouldn't it be cool

[slew]

FWIW, it appears from the paper that this extra "mass" is an artifact of analyzing entangled particles in a linearized gravity framework and observing a stress-energy tensor term that seems to appear higher for entangled particles and radiated away as particles move to decoherence. This perhaps might be considered the mass of the entanglement.

On the other hand, wouldn't it be cool if the reason for the observed equivalency of gravitational mass and inertial mass was somehow related to quantum entanglement? (yes I know this is unrelated to this phenomena, but still)...

Re:wouldn't it be cool

[PopeRatzo]

it appears from the paper that this extra "mass" is an artifact of analyzing entangled particles in a linearized gravity [wikipedia.org] framework and observing a stress-energy tensor term that seems to appear higher for entangled particles and radiated away as particles move to decoherence.

Right? I was just gonna say that.

Re:wouldn't it be cool

[mbone]

Is it really a motional term (i.e., due to a higher level of quantum jitter)?

Re:wouldn't it be cool

[binarylarry]

Dude that would be so cool!

Re:wouldn't it be cool

[drolli]

I looked at the paper and i have the feeling that they misuse the term "entangled". At least their definition of the density operator seems dodgy. If they would not say it's entangled i would call it a superposition state of a single particle.

Which, in terms of the density matrix is not so different. But we experimentalists usually require two particles with multiple states to use the word "entanglement".

Moreover, since they are comparing a mixed state, i would find it particularly interesting if there is a difference in the Energy Expectation value for realistic Hamiltonians. (If yes, i would not wonder so much about a mass defect).

Not

[mbone]

Entanglement Makes Quantum Particles Measurably Heavier

One part in 10^37 is not measurably heavier. No measurement in science has anything like 37 significant figures*.

*No, the cosmological constant does not count, as it was not measured from quantum principles, but from cosmological ones.

I'm not fat...

[bananaquackmoo]

I'm not fat, I'm quantum entangled!

Re:I'm not fat...

[Anonymous Coward]

Shut up Cartman!

Re:I'm not fat...

[willworkforbeer]

No, you're so fat you're in two places at once.

Holy Fucking WRONG

[sexconker]

The discovery is based on the long-known quantum phenomenon in which a single particle can be in two places at the same time.

Wrooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong.

Re:Holy Fucking WRONG

[swillden]

The discovery is based on the long-known quantum phenomenon in which a single particle can be in two places at the same time.

Wrooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong.

Right. The long-known phenomenon is that a single particle can have two velocities at the same time. Sheesh.

Re:Holy Fucking WRONG

[Anonymous Coward]

WTF is a "particle"?

"I know it all", said the wave to the ocean.

Re:Holy Fucking WRONG

[Anonymous Coward]

This gets modded up? The only way you could argue the quote was wrong is that technically the particle is in an infinite number of places at a time since the wavefunction is continuous over some volume, but still effectively behaves like it is in two places at a time, for everything from the two-slit experiment to the Aharonov–Bohm effect.

Re:Holy Fucking WRONG

[sexconker]

It doesn't "behave" in any way until you interact with it. It doesn't exist "in two places at the same time".

Re:Holy Fucking WRONG

[Anonymous Coward]

It doesn't "behave" in any way until you interact with it.

It has a time history, even if it is rather complicated compared to a Newtonian trajectory, and evolves over time. It behaves without interaction. Additionally, it can interact with a closed system before an observation or other outside interaction affects it.

It doesn't exist "in two places at the same time".

You say it again, without any justification, and in spite of things already pointed out like the Aharonov-Bohm effect, which requires a particle to have followed different paths around a magnetic field. You can build things like single particle interferometers, and have a particle interact with components of both legs.

Re:Holy Fucking WRONG

[Anonymous Coward]

Maybe you should look into some the effects named, or something more fundamental like path integral formulation of quantum mechanics before just trying to throw things out.

The real question they need to answer is:

[Anonymous Coward]

If an entangled particle becomes disentangled and loses that extra weight, how long before it gains all of it's weight back?

This would explain a lot of things!

We can use dehydration, laxatives, acceleration to near the speed of light and carb restriction on this particle and see if it still is entangled..

We're gonna need a bigger lab

[Anonymous Coward]

Would the overall observable mass of the entangled particles increase with distance? What about in two different reference frames of time, like say a particle orbiting the earth entangled with a stationary one on its surface?

And

[Richy_T]

Leon's getting larger.

Re:Interesting use of measurable

[Anonymous Coward]

Besides not seeing the trees and not the forest by ignoring the whole bit about the one part in 10^37 not being the likely target of measurement, the uncertainty principle as such doesn't apply to just a measurement of mass as momentum is not as simple as mass times velocity in quantum mechanics (or relativity either). Additionally, it would not apply to ensembled measurements, such as a large number of weak measurements on a repeatable experiment.

Momentum, not mass

[rjh]

The photon has zero rest mass, yes.

E = mc**2 is a nice popularization; it's also wrong. It's actually E**2=(mc**2)**2 + (pc)**2, where p is the momentum. When momentum is zero, you can usually simplify this to E=mc**2, but a photon's existence is defined mostly by its momentum. Since m is zero for a photon, this means the energy of a photon is given by entirely by E=pc.

Hope this helps!

Re:Interesting use of measurable

[Crashmarik]

You're right it's even worse in qm. I am curious why you didn't mention that ?

Oh hell let me put this in a way you can grasp

[Crashmarik]

The amount of change in mass you would be trying to detect is less than what the uncertainty principle allows for the creation of virtual particles over the length of time any reasonable experiment could run. Good luck with that.

Re:Oh hell let me put this in a way you can grasp

[Anonymous Coward]

The ability for virtual particles to affect measurements is already inherent in the mass of particles as we measure it, as it is part of the basic propagator in QFT. The uncertainty principle doesn't change or limit that, nor would that be an issue for relative measurements.

Quantum entanglement IS the gravity we experience

[Anonymous Coward]

Quantum entanglement IS the gravity we experience

encryption

[StripedCow]

Didn't RTFA, but still wondering: does this mean quantum encryption can be beaten by adding a "weight scale" to the transmission link?

I'm not fat

[lars5]

I'm just really quantumly entangled.

Misapplied Bullshit meter

[John.Banister]

If you read the pdf from arxiv you might learn that this is the work of a theoretician. He does the math. He doesn't attempt to measure anything.

not real

[micahraleigh]

I don't buy it.

It takes about 8 minutes for the gravity from the sun to reach the earth, but quantum phenomena would travel instantaneously.

Different things.

That's a little anecdotal, but all truth is on some level.

Re:not real

[Anonymous Coward]

If by "Different things" you mean completely irrelevant because nothing in the stated effect would change how fast gravity travel or allow instantaneous communication... Truth, on any level, isn't irrelevant stories.

Re:not real

[micahraleigh]

Who said anything about communication? Quantum effects travel instantaneously. That's (part of what) spooked Einstein.

I would expect quantum and gravitational effects to travel at the same speed viz. Ockham's razor.

A more complex explanation could model it, but something more would be needed to persuade me.

Re:not real

[Anonymous Coward]

I would expect quantum and gravitational effects to travel at the same speed viz. Ockham's razor.

On what basis? Ockham's razor alone is not a justification for a claim. The only established theory that says anything about the speed of gravitational effects is general relativity, which limits it to the speed of light. Experiments so far have agreed with this. Current attempts at quantum gravity retain the speed limit. Ockham's razor doesn't help you with a claim that is baseless.

Who said anything about communication? Quantum effects travel instantaneously.

Very specific kinds of quantum effects travel instantaneously, and do so in a way that prevent communication of information instantaneously. Suggesting that gravitation effects can travel instantaneously in any sort of general sense would allow for communication in a way not possible with quantum mechanics.

And as the previous AC said, this is all irrelevant to the paper brought up here, because it does not propose quantum effects that would cause instantaneous changes in gravity.