Physicists use Einstein's 'spooky' entanglement to invent super-sensitive gravitational wave detector

May 17, 2017 by David Blair, The Conversation
When black holes collide, gravitational waves are created in space itself (image is a computer simulation). Credit: The SXS (Simulating eXtreme Spacetimes) Project

The first direct detection of gravitational waves, a phenomenon predicted by Einstein's 1915 general theory of relativity, was reported by scientists in 2016.

Armed with this "discovery of the century", physicists around the world have been planning new and better detectors of gravitational waves.

Physicist Professor Chunnong Zhao and his recent PhD students Haixing Miao and Yiqiu Ma are members of an international team that has created a particularly exciting new design for gravitational wave detectors.

The new design is a real breakthrough because it can measure signals below a limit that was previously believed to be an insurmountable barrier. Physicists call this limit the . It is set by the quantum uncertainty principle.

The new design, published in Nature magazine this week, shows that this may not be a barrier any longer.

Using this and other new approaches may allow scientists to monitor black hole collisions and "spacequakes" across the whole of the visible universe.

How gravitational wave detectors work

Gravitational waves are not vibrations travelling through space, but rather vibrations of space itself. They have already told us about an unexpectedly large population of black holes. We hope that further study of gravitational waves will help us to better understand our universe.

But the technologies of gravitational wave detectors are likely to have enormous significance beyond this aspect of science, because in themselves they are teaching us how to measure unbelievably tiny amounts of energy.

Gravitational wave detectors use laser light to pick up tiny vibrations of space created when black holes collide. The collisions create vast gravitational explosions. They are the biggest explosions known in the universe, converting mass directly into vibrations of pure space.

It takes huge amounts of energy to make space bend and ripple. Our detectors – exquisitely perfect devices that use big heavy mirrors with scarily powerful lasers – must measure space stretching by a mere billionth of a billionth of a metre over the four kilometre scale of our detectors. These measurements already represent the smallest amount of energy ever measured.

But for gravitational wave astronomers this is not good enough. They need even more sensitivity to be able to hear many more predicted gravitational "sounds", including the sound of the moment the universe was created in the big bang.

This is where the new design comes in.

A spooky idea from Einstein

The novel concept is founded on original work from Albert Einstein.

In 1935 Albert Einstein and co-workers Boris Podolsky and Nathan Rosen tried to depose the theory of mechanics by showing that it predicted absurd correlations between widely spaced particles.

Einstein proved that if quantum theory was correct, then pairs of widely spaced objects could be entangled like two flies tangled up in a spider's web. Weirdly, the entanglement did not diminish, however far apart you allowed the objects to move.

Einstein called entanglement "spooky action at a distance". He was sure that his discovery would do away with the theory of quantum mechanics once and for all, but this was not to be.

Since the 1980s physicists have demonstrated time and again that is real. However much he hated it, Einstein's prediction was right and to his chagrin, quantum theory was correct. Things at a distance could be entangled.

Today physicists have got used to the "spookiness", and the theory of entanglement has been harnessed for the sending of secret codes that cannot be intercepted.

Around the world, organisations such as Google and IBM and academic laboratories are trying to create quantum computers that depend on entanglement.

And now Zhao and colleagues want to use the concept of entanglement to create the new 's design.

A new way to measure gravitational waves

The exciting aspect of the new design is that it is actually just a new way of operating existing detectors. It simply uses the detector twice.

One time, photons in the detector are altered by the gravitational wave so as to pick up the waves. The second time, the detector is used to change the quantum entanglement in such a way that the noise due to quantum uncertainty is not detected.

The only thing that is detected is the motion of the distant mirrors caused by the gravitational wave. The quantum noise from the uncertainty principle does not appear in the measurement.

To make it work, you have to start with entangled photons that are created by a device called a quantum squeezer. This technology was pioneered for gravitational wave astronomy at Australian National University, and is now an established technique.

Like many of the best ideas, the new idea is a very simple one, but one that took enormous insight to recognise. You inject a miniscule amount of squeezed light from a quantum squeezer, and use it twice!

Around the world physicists are getting ready to test the new theory and find the best way of implementing it in their detectors. One of these is the GEO gravitational wave detector at Hannover in Germany, which has been a test bed for many of the new technologies that allowed last year's momentous discovery of .

Explore further: 'Listening' to black holes form with gravity waves

More information: Yiqiu Ma et al. Proposal for gravitational-wave detection beyond the standard quantum limit through EPR entanglement, Nature Physics (2017). DOI: 10.1038/nphys4118

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xinhangshen
1 / 5 (6) May 18, 2017
Unfortunately, there does not exists such a thing called 4D spacetime in nature and thus no spacetime vibration because Einstein's relativity theory has already been disproved both logically and experimentally (see "Challenge to the special theory of relativity", March 1, 2016 and a press release on Eurekalert website: https://www.eurek...16.php).

The most obvious and indisputable experimental evidence, which everybody with basic knowledge of special relativity should immediately understand: is the existence of the absolute time shown by the universally synchronized clocks on the GPS satellites which move at high velocities relative to each other while special relativity claims that time is relative (i.e. the time on each reference frame is different) and can never be synchronized on clocks moving with relative velocities.
Gigel
5 / 5 (5) May 20, 2017
Hafele–Keating experiment: https://en.wikipe...periment

The Hafele–Keating experiment was a test of the theory of relativity. In October 1971, Joseph C. Hafele, a physicist, and Richard E. Keating, an astronomer, took four cesium-beam atomic clocks aboard commercial airliners. They flew twice around the world, first eastward, then westward, and compared the clocks against others that remained at the United States Naval Observatory. When reunited, the three sets of clocks were found to disagree with one another, and their differences were consistent with the predictions of special and general relativity.
Da Schneib
5 / 5 (1) May 21, 2017
Geez, 1971. That was, what, 45 or 50 years ago? Shame the physics cranks can't keep up with modern physics so they're at least denying something that hasn't been proven since before they were born.
Da Schneib
5 / 5 (1) May 21, 2017
It would be interesting and informative to see exactly how they're using entanglement to cancel Heisenberg uncertainty. I'll go look and see if I can figure it out.
Da Schneib
5 / 5 (2) May 21, 2017
The open link: https://arxiv.org...6934.pdf

Still analyzing. Looks pretty good so far. The explanation might go into signal processing.
sascoflame
1 / 5 (1) May 22, 2017
1. One time, photons in the detector are altered by the gravitational wave so as to pick up the waves. The second time, the detector is used to change the quantum entanglement in such a way that the noise due to quantum uncertainty is not detected.

This statement is meaningless. It says it gets rid of quantum noise but doesn't it say how.

2. Niels Bohr discovered quantum entanglement. The article tells the absurd lie that Einstein discovered quantum entanglement and argued that is did not exist. That is a contradiction in terms. Einstein did claim there was something called a cosmological constant and later argued against it. That is an absurd stretch but to give in credit for quantum entanglement means that next we will give him credit for all of Newton.

If a freshman turned this in he would get an "f."

Read more at: https://phys.org/...html#jCp
richdiggins
not rated yet May 22, 2017
Geez, 1971. That was, what, 45 or 50 years ago? Shame the physics cranks can't keep up with modern physics so they're at least denying something that hasn't been proven since before they were born.


Oh, wait... so it is the Law of Relativity now? ...
swordsman
1 / 5 (1) May 22, 2017
Many flaws in these assumptions shows a nearly complete misunderstanding of electromagnetic waves. Radiating electromagnetic waves are not spherical, but this false assumption was the basis of Einstein;s theory. Electromagnetic waves obey the law of "superposition" in which they simply add and attract in vector space. Gravitational waves are indeed electromagnetic waves, and they do indeed obey the law of superposition. Wasted effort.
xinhangshen
1 / 5 (1) May 23, 2017
The displayed times of the clocks in H-K experiment are absolute no matter where you observe them. It is a misinterpretation by relativists that the differences of the clock times are caused by relativistic time dilation. Actually the differences are caused by the differences of their paths (1: on the earth, 2: westward around the earth and 3: eastward around the earth). On these different paths, there is something making the atomic clocks tick in different rates, which is irrelevant to where you observe them. This something is what we call aether. It is the velocity of a clock relative to aether (not the velocity relative to the observer as claimed by special relativity) that determines the ticking rate of the clock. On the earth surface, aether is nearly 100% dragged by the earth, but on an airplane with an altitude, aether is no longer 100% dragged by the earth. Therefore, there are different ticking rates after different paths, nothing to do with relativity.
Whydening Gyre
not rated yet May 23, 2017
... On the earth surface, aether is nearly 100% dragged by the earth, but on an airplane with an altitude, aether is no longer 100% dragged by the earth. Therefore, there are different ticking rates after different paths, nothing to do with relativity.

The paths were relative to each other...
Gigel
5 / 5 (2) May 24, 2017
If displayed times are absolute, then they should be the same, no matter the aether or anything else. There should be no difference between them. If they are not the same, then they are not absolute. Unless you mean something else by "absolute". Nevermind, you go on my ignore list.
antialias_physorg
5 / 5 (2) May 24, 2017
On the earth surface, aether is nearly 100% dragged by the earth, but on an airplane with an altitude, aether is no longer 100% dragged by the earth

Question: which direction is this 'aether' dragged in? In direction of rotation? Against it? At right angles?

Because if there was an aether then we'd see different effects depending on which direction the airplane is moving (with the direction of drag or against it).

(Hint: this is what Michelson-Morely was trying to test for - and consequently disproved)
Dingbone
May 24, 2017
This comment has been removed by a moderator.
antialias_physorg
not rated yet May 24, 2017
You cannot detect aether drift

Aaaah...so why yre you saing it's drifting if that drift is undetectable? Hint: stuff that isn't detectable doesn't exist.

aether would be completely superfluid

The word superfuild doesn't mean what you think it means. And the actual definition of superfluidity doesn't apply here (moving through a superfluid would be EXTREMLY well detectable).
xinhangshen
1 / 5 (1) May 24, 2017
If displayed times are absolute, then they should be the same, no matter the aether or anything else. There should be no difference between them. If they are not the same, then they are not absolute. Unless you mean something else by "absolute". Nevermind, you go on my ignore list.


No, you are wrong. Many factors can make atomic clocks function differently, just like your wrist watches which can be influenced by temperature, radiation, electromagnetic fields, gravitation, acceleration, the velocity relative to aether, etc. What I want emphasize is the changes are absolute and can be corrected to make the clocks synchronized, while relativistic kinematic time dilation caused clock differences are relative to observers and can't be corrected to make the clocks synchronized in all reference frames.
Da Schneib
not rated yet May 25, 2017
I've reviewed this now as much as I can, and the proposal seems credible. The additional equipment required is fairly minimal. This is a very innovative application of quantum optics, and it appears that they can, in fact, overcome the quantum limits as they claim. I'll be interested to see whether this gets put into aLIGO.
vacuumforce
not rated yet Jun 29, 2017
spacetime is just nothing, as in not matter or energy

I do not think we can make a direct observation of nothing.

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