"The holometer"-- experimentally testing the holographic principle?

Coin

Several popular-science type news sources are reporting this weekend on an experiment at Fermilab that claims to experimentally test the holographic principle..

Researchers at Fermilab are building a “holometer” so they can disprove everything you thought you knew about the universe. More specifically, they are trying to either prove or disprove the somewhat mind-bending notion that the third dimension doesn’t exist at all, and that the 3-D universe we think we live in is nothing more than a hologram. To do so, they are building the most precise clock ever created.

Popsci then says a bunch of vague stuff that sounds like they didn't fully understand the information Fermilab gave them. The official page for the experiment goes into more detail, but not much more...

More recently, theoretical studies of black holes, and later in string theory and other forms of unification, have suggested that physics on the Planck scale is holographic. It is conjectured that space is two dimensional, and the third dimension is inextricably linked with time. If so, our three-dimensional world is a kind of approximate illusion that emerges only on scales much larger than the Planck length.

It could be that the illusion is imperfect and blurry. The maximum frequency may introduce a particular kind of noise or jitter into spacetime, as measured by the propagation of light in different directions.

The holometer attempts a direct experimental test of one form of this hypothesis. In a Michelson interferometer, a light beam is split into two parts that travel in different directions, then are brought back together. The vibrations of light in the two directions tend to drift apart by about Planck length per Planck time when they are traveling in different directions. When they are recombined, the difference in light phase can be measured. In the holometer, signals from two different interferometers -- that is, two completely separate systems, each with its own pair of beam arms -- are compared. If they are close enough to probe the same volume of spacetime -- that is, if light in both systems is travelling in about the same direction, at about the same time -- their signals should display the same, correlated jitter, sometimes called "holographic noise".

The official page says they are still in the design phase, the popsci article says construction on the device has begun.

So:

Is this for-real or is some of this hype?

Has an experiment of this type ever been attempted before?

They say they're testing "one form" of the hypothesis. I assume this means they can't falsify the holographic principle through this method. How likely is it that if the holographic principle is true, then holographic jitter is true, and how likely is it that if holographic jitter is real then this experiment will find it? Or in short, if the results of the holometer experiment is negative, what would that tell us?

Have any of the "real" physics blogs picked this one up yet?

atyy

Googling gives

http://arxiv.org/abs/0806.0665
http://arxiv.org/abs/0812.1285

Seems real (ie. not cranks), though I am skeptical.

marcus

Quote by Coin

Several popular-science type news sources are reporting...

Have any of the "real" physics blogs picked this one up yet?

Bee Hossenfelder "Backreaction" 1 March 2009
http://backreaction.blogspot.com/200...hic-noise.html

Bee Hossenfelder 21 September 2009
http://backreaction.blogspot.com/200...ery-noise.html

Here is Craig Hogan's most recent article about this idea, initially dated February 2010:
http://arxiv.org/abs/1002.4880
It has gone thru 7 versions over the past 8 months. It not published except as a Fermilab report.
He has quite a few papers about the idea going back at least to 2008 (as Atyy pointed out)
http://arxiv.org/find/gr-qc/1/au:+Hogan_C/0/1/0/all/0/1

As I recall Hogan got quite a lot of attention back in 2008 when he hypothesized that (in a German interferometer GEO intended as gravitational wave detetector) some unexplained noise
could be due to the holographicness of the world---could be "holographic noise".

This was reported by Woit in Not Even Wrong on a few occasions as I recall. You might be able to find more details of the story there.

Hogan has 82 papers on arxiv going back to 1994, when for example he published a solo paper in Physical Review Letters. I think it is obvious that he is highly regarded. He gets a lot of ideas in a lot of different fields. They don't always work out but clearly people do pay attention.

Coin

Great, thanks so much all. I remembered hearing about the earlier "gravity wave noise" result but wasn't sure if this was the same thing or not.

Also now armed with the appropriate additional search terms, I find why there were several mainstream-news articles about this at the end of last week all at once-- fermilab published a piece in their official magazine. The piece is actually quite good, and confirms the sequence of events that Hogan used his claim about the GEO data to get the holometer experiment greenlighted in the first place. It also gives some concrete data on timeline...

This month, having successfully built a 1-meter prototype of the 40-meter arm, they will weld the parts of the first of the vacuum arms together. Hogan expects the holometer to begin collecting data next year.

The article also clarifies something I hadn't understood: The "holometer" in fact should double as a gravity wave detector, each of the two 40-meter inferometers in the holometer is effectively a gravity wave detector set to detect gravity waves of very high frequency...

( Totally offtopic: Bee's pregnancy countdown banner still kind of freaks me out. It looks like it is implying the girls are going to be bursting out of her stomach... -_-; )

marcus

Quote by Coin

...
( Totally offtopic: Bee's pregnancy countdown banner still kind of freaks me out. It looks like it is implying the girls are going to be bursting out of her stomach... -_-; )

http://backreaction.blogspot.com/2010/09/112.html

crackjack

Why only at Planck scale? Isn't holography conjectured at even as low as ~eV (a la AdS/CMT)?

czes

May be this problem is similar to Turing test:
If the judge cannot reliably tell the machine from the human, the machine is said to have passed the test.

If we can not distinguish between Holographic Universe and Matter Universe it means we live in the Holographic one because it is simpler - just an information and math.

*waterfall*

This February. This is the cover story of Scientific American which brought it to the attention of the wider public so it's appropriate to rediscuss this old topic (I just read the article last night).

http://www.scientificamerican.com/ar...-space-digital

http://www.symmetrymagazine.org/brea...phic-universe/

First, is it mainstream? Do Scientific American discuss only mainstream ideas?
Second. Do you think the device will work? If a train moves hundred of miles away, it can introduce a planck size jitter... so can they make it sensitive enough with filtering electronics to actually isolate the noise from the signal? Do you have confidence the holometer can be successfully built?

Third. If it would be proven. Would it support LQG? But how do you tie up the idea of holographic principle in the spin networks and spin foam in LQG. And when will there be definite results?

I think if proven true. It would have impact much like the MMX experiment in the early 1900 that falsity the aether theory.

czes

I think we have to distinguish the foamy and digital space. The foamy space refers to a kind of an aether and a distance made of the grains of the space. The digital space shows an illusion of the distance as in the quantum information.

The quantum event in digital space doesn't mean a relation between the physical particles of the space but there is a relation between the numbers of a pure math. Therefore we observe the conservation of the information from the farthest galaxy. The only change in a quantum event is the delay of the the Planck time, nothing more.
The polarization of the light remains the same though the length of the wave depends on the relative density of the information in that space.

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atyy Recognitions: Science Advisor	Googling gives http://arxiv.org/abs/0806.0665 http://arxiv.org/abs/0812.1285 Seems real (ie. not cranks), though I am skeptical.

crackjack	Why only at Planck scale? Isn't holography conjectured at even as low as ~eV (a la AdS/CMT)?

czes	May be this problem is similar to Turing test: If the judge cannot reliably tell the machine from the human, the machine is said to have passed the test. If we can not distinguish between Holographic Universe and Matter Universe it means we live in the Holographic one because it is simpler - just an information and math.