Gravitational Waves

Chipper Q
Chipper Q
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RE: RE: I have a

Message 79488 in response to message 79487

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I have a question for this linear thinker who has a hard time getting his head around general relativity:-).

Join the club! Incidentally linear is a key word here, so do read on ...... :-)


Is it linear thinking when you think inside the box, or outside the box? And what of those who think there is no box? :))

As if the whole of relativity isn't enough to try and wrap your mind around (and as a follow-up on an earlier post of mine on different efforts to directly detect GWs), try this one on for size: Detection of Gravitational Wave – An Application of Relativistic Quantum Information Theory

Anyone have any thoughts on that approach? For instance, could the LIGO scientists piggyback some entangled massive spin-1/2 particles down the arms of the interferometers and check for a change in spin entropy? And for crunchers/hackers/home-brewers would it be possible to make a GW sensor that would fit on the work bench, and then upload data (relative to each specific location & time) to be crunched?

One thing I know for sure about 'the box' is all mine are crunching for EatH :)

Mike Hewson
Mike Hewson
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RE: Is it linear thinking

Message 79489 in response to message 79488

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Is it linear thinking when you think inside the box, or outside the box? And what of those who think there is no box? :))


Linear thinking is when you drive straight through the steel barriers instead of turning the corner! :-)

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As if the whole of relativity isn't enough to try and wrap your mind around (and as a follow-up on an earlier post of mine on different efforts to directly detect GWs), try this one on for size: Detection of Gravitational Wave – An Application of Relativistic Quantum Information Theory


I think it means that for certain particles momentum and spin state are reliably related. GW's affect their momentum, thus their spin. You start with entangled pairs, and one of each pair is sent on some traverse up an arm. You can't measure each pair's difference upon return, so you do population counts comparing those that 'stayed home' vs. those that 'went to market'. A passing GW will cause a difference in the numbers here - pushing away from an equilibrium state as it imparts energy to some particles to change their momentum/spin - this trend is coined as 'negative entropy'.

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Anyone have any thoughts on that approach? For instance, could the LIGO scientists piggyback some entangled massive spin-1/2 particles down the arms of the interferometers and check for a change in spin entropy? And for crunchers/hackers/home-brewers would it be possible to make a GW sensor that would fit on the work bench, and then upload data (relative to each specific location & time) to be crunched?


Well, it would be swapping photon phase changes for particle-X spin changes. The photon changes at present come out as electrical current via some photodiodes, whereas the spin changes would measurably convert to what via what? I think the chosen detector technology is well understood.

Cheers, Mike.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Rod
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RE: RE: Is it linear

Message 79490 in response to message 79489

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Is it linear thinking when you think inside the box, or outside the box? And what of those who think there is no box? :))

Linear thinking is when you drive straight through the steel barriers instead of turning the corner! :-)

Cheers, Mike.

Sorry Guys.. This is what linear thinking is about:-)
Linear Thinking

There are some who can live without wild things and some who cannot. - Aldo Leopold

Chipper Q
Chipper Q
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RE: RE: RE: Is it

Message 79491 in response to message 79490

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Is it linear thinking when you think inside the box, or outside the box? And what of those who think there is no box? :))

Linear thinking is when you drive straight through the steel barriers instead of turning the corner! :-)

Cheers, Mike.

Sorry Guys.. This is what linear thinking is about:-)
Linear Thinking


lol! - that looks like how I do a lot of my thinking – clamoring atop shoulders with minds way brighter than mine, hoping to make sense from the view :))

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Well, it would be swapping photon phase changes for particle-X spin changes. The photon changes at present come out as electrical current via some photodiodes, whereas the spin changes would measurably convert to what via what? I think the chosen detector technology is well understood.


oops, I didn't mean to imply swapping anything – I borrowed the phrase 'piggyback' from that link on Doppler tracking (where they included the gravitational wave science in a collaborated 'piggyback' fashion aboard a sciencecraft already having a primary mission). I was wondering if it would be possible (or practical) to include a particle beam (composed of the massive spin-1/2 particles), separate from the optics and without disturbing the regular operation of the interferometer. Probably not :) But after rereading the paper, it's assumed 'that the spacetime curvature doesn't change drastically within the spacetime scale of the wave packet,' so that sounds like it's a measurement not requiring a lot of area to begin with (or that too much of an interval becomes detrimental to the measurement).

Good question about measuring what via what - I'm guessing a suitable quantum GW sensor (as distinct from a quantum GW detector, where a proper detector is composed of a network of the sensors) would be a variation on some type of quantum computing architecture that facilitates entanglement with the particles serving as test masses (the particle-X's), and then performs enough entanglement swapping to sufficiently amplify any decoherence effect that would be due solely to a passing gravitational wave. I'll do some more checking when I get the chance, as that paper is already two years old now, and I still don't see any reason why a sensor like that couldn't be made to fit in a small enough package to sit on the bench top... couldn't it? I wonder what's been done in the last couple years to determine if it's a viable approach...?

Mike Hewson
Mike Hewson
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RE: lol! - that looks like

Message 79492 in response to message 79491

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lol! - that looks like how I do a lot of my thinking – clamoring atop shoulders with minds way brighter than mine, hoping to make sense from the view :))


Yeah, good old Sesame Street!! :-)

Speaking of linear thinking .....

Q. How do you get a giraffe in a fridge?

A. Open the door, put it in and close the door.

Q. How do you get an elephant into a fridge?

A. Open the door, take out the giraffe, put the elephant in and then close the door.

Q. The Lion King holds a conference of all the animals. Who didn't turn up?

A. The elephant, because he was in the fridge.

Q. You come to one of the rivers in the jungle, which is known to be crocodile infested. You must cross it, but how do you do that without being eaten?

A. Jump in and swim across ( the croc's are at the Lion King's conference ..... aren't you listening? ).

It is rumoured that 4 year olds perform better at these questions than most adult professional groups ( they tend to generate complex answers ). So stockbrokers, for instance, will be pleased to know that they don't have the minds of 4 year olds .... :-)

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Well, it would be swapping photon phase changes for particle-X spin changes. The photon changes at present come out as electrical current via some photodiodes, whereas the spin changes would measurably convert to what via what? I think the chosen detector technology is well understood.


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oops, I didn't mean to imply swapping anything – I borrowed the phrase 'piggyback' from that link on Doppler tracking (where they included the gravitational wave science in a collaborated 'piggyback' fashion aboard a sciencecraft already having a primary mission). I was wondering if it would be possible (or practical) to include a particle beam (composed of the massive spin-1/2 particles), separate from the optics and without disturbing the regular operation of the interferometer. Probably not :) But after rereading the paper, it's assumed 'that the spacetime curvature doesn't change drastically within the spacetime scale of the wave packet,' so that sounds like it's a measurement not requiring a lot of area to begin with (or that too much of an interval becomes detrimental to the measurement).


Well I think the LIGO vacuum spaces were deliberately generously designed, in anticipation of provision of some as yet unknown techniques/technology in the long haul. For instance, I think the next science run is going to be done with some of the feedback control optics tables in the vacuum space. I couldn't quite see if the particle-X idea was to make an absolute measurement ( ? calibration ), or whether it was a null-type procedure ( as LIGO currently is ).

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Good question about measuring what via what - I'm guessing a suitable quantum GW sensor (as distinct from a quantum GW detector, where a proper detector is composed of a network of the sensors) would be a variation on some type of quantum computing architecture that facilitates entanglement with the particles serving as test masses (the particle-X's), and then performs enough entanglement swapping to sufficiently amplify any decoherence effect that would be due solely to a passing gravitational wave. I'll do some more checking when I get the chance, as that paper is already two years old now, and I still don't see any reason why a sensor like that couldn't be made to fit in a small enough package to sit on the bench top... couldn't it? I wonder what's been done in the last couple years to determine if it's a viable approach...?


Ultimately the measurement I think has to come out in electronic form, meaning this shift of spin states in the population of the particle-X's needs to be transduced to that. They describe, I think, a time succession of harvests of fractions of an initially coherent group of particles. Each subset is examined with respect to the first to deduce some spin shift that has accumulated due to the wave passage. They are approximating a curved spacetime line ( ie. general relativity ) with a sequence of local Lorentz 'boosts' ( ie. special relativity ). Is this valid? Are they neatly avoiding discussing GR with QM, a known difficult mix? You see the spacetime strain is of the order of 10^(-21), so what negative entropy shift does that produce in said particles, then what is the shift order? In the tenth decimal place? Twentieth? Fiftieth? I couldn't clearly see that we were getting more sensitivity to the base effect rather than less.... quite interesting none-the-less :-)

Cheers, Mike.

[ edit ] By the way, I've just noticed that H2 is still taking data! I forgot they were going to stay up during the upgrades, and their GRB linkage is still active too. I'll look into this some more .... :-)

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Chipper Q
Chipper Q
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RE: I couldn't quite see if

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I couldn't quite see if the particle-X idea was to make an absolute measurement ( ? calibration ), or whether it was a null-type procedure ( as LIGO currently is ).


It was mentioned that, in principle, the technique could be used to deduce the size and shape of a propagating ripple in the curvature of spacetime (I think by measuring the “negativity� of the spin entropy at a number of locations along an interval, where each 'static observer ... is assigned a local inertial frame ...') So going from the inertial frame of the ripple to the inertial frame of the observer would require using the maths of special relativity, right? Hence the Lorentz boost, or continuous succession of them, resulting in environmental decoherence and production of the spin entropy that is unique to the curvature of the spacetime. If it is valid, I don't see how it could get any more sensitive than that. I'm guessing that the entropy data would be collected by passing the (swapped n-times) entangled particles through an inhomogeneous magnetic field, like the Stern-Gerlach experiment.

I've been trying to find out more about the entanglement swapping, and found some 'spooky' stuff, to be sure: Experimental Nonlocality Proof of Quantum Teleportation and Entanglement Swapping
I've heard of “Where does the time go?�, but that experiment seems to make a moot point of time. Scary! So does that mean the data could be processed at a leisurely rate, or whatever rate that the processing hardware performs at (since the entanglement is preserved in the swapping), long after the original test mass particle was subjected to the local spacetime curvature...?

Thanks for the update on H2!

Chipper Q
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Oy, hold on – so many open

Oy, hold on – so many open tabs in the browser as I've been checking on this that the tab with the article that cited the paper got pushed out of view, and now after getting back to it and reading the rest of the article (Spotting the quantum tracks of gravity waves), there's a fairly discouraging opinion right at the end saying that '...to get something observable you would need a gravity field so large that it would rip your lab apart...', and that includes using the amplification from entanglement swapping. Yet the paper mentions that the ideas were first illustrated with the Schwarzschild spacetime, and still acknowledges that the amplitude of gravitational waves may only be of order 10^-21. It looks like the validity isn't in dispute at all, but rather the sensitivity from the amplification is in question... I'll keep checking...

Mike Hewson
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RE: Oy, hold on ...........

Message 79495 in response to message 79494

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Oy, hold on ........... there's a fairly discouraging opinion right at the end saying that '...to get something observable you would need a gravity field so large that it would rip your lab apart...', and that includes using the amplification from entanglement swapping .....


Ahhh, that's a bummer. The old gravity gradient! Sort of like 'between two neutron stars' type of scenario. One wonders whether the entanglement would remain undisturbed with such energy drops abounding - you might get a glow of Hawking radiation and all that other peri-black-hole-horizon stuff. In the ( pathetically brief ) time you'd have to perform the experiment you could directly measure some much easier to see human scale effect of the wave without pffaffing about with quantum pernicketies ...... like the percentage change in your leg length for instance ..... :-)

Cheers, Mike.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

tullio
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Interesting link at LHC@home

Interesting link at LHC@home messages science:
superstrings
Tullio

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