Quantum entangled photons react to Earth's spin | Hacker News Reader

Quantum entangled photons react to Earth's spin

phys.org

130 pointswglb32 comments

> "The core of the matter lays in establishing a reference point for our measurement, where light remains unaffected by Earth's rotational effect. Given our inability to halt Earth's from spinning, we devised a workaround: splitting the optical fiber into two equal-length coils and connecting them via an optical switch," explains lead author Raffaele Silvestri.

> By toggling the switch on and off, the researchers could effectively cancel the rotation signal at will, which also allowed them to extend the stability of their large apparatus. "We have basically tricked the light into thinking it's in a non-rotating universe," says Silvestri.

"Experimental observation of Earth's rotation with quantum entanglement" (2024) https://www.science.org/doi/10.1126/sciadv.ado0215

Sagnac interferometer: https://en.wikipedia.org/wiki/Sagnac_effect

Given our inability to halt Earth's from spinning

Good to have some baseline assumptions!

So almost like an optical wheatstone bridge ?

Wheatstone bridge > Modifications of the basic bridge: https://en.wikipedia.org/wiki/Wheatstone_bridge#Modification... :

> Carey Foster bridge, for measuring small resistances; Kelvin bridge, for measuring small four-terminal resistances; Maxwell bridge, and Wien bridge for measuring reactive components; Anderson's bridge, for measuring the self-inductance of the circuit, an advanced form of Maxwell's bridge

Is there a rectifier for gravitational waves, and what would that do?

Diode bridge > Current flow: https://en.wikipedia.org/wiki/Diode_bridge#Current_flow

And actually again, electron flow is fluidic:

- "How does electricity find the "Path of Least Resistance"?" (and the other paths) https://www.youtube.com/watch?v=C3gnNpYK3lo

- "Observation of current whirlpools in graphene at room temperature" (2024) https://news.ycombinator.com/item?id=40360684 :

> How are spin currents and vorticity in electron vortices related?

But, back to photons from electrons; like in a wheatstone bridge.

Are photonic fields best described with rays, waves, or as fluids in gravitational vortices like in SPH and SQS and CFD? (Superhydrodynamic, Superfluid Quantum Space, Computational Fluid Dynamics)

Actually, photons do interact with photons; as phonons in matter: "Quantum vortices of strongly interacting photons" (2024) https://www.science.org/doi/10.1126/science.adh5315 https://news.ycombinator.com/item?id=40600762

Perhaps there's an even simpler sensor apparatus for this experiment?

This got me thinking about the old concept of the ether, which was supposedly debunked by the Michelson-Morley experiment. However, I don't think that experiment completely disproved the existence of the ether – it just showed that the classical ether theories were inconsistent with the observed constancy of the speed of light.

What if we consider the quantum vacuum, with its virtual particles and fluctuations, as a modern version of the ether? In that case, could the rotation of the Earth interact with this "quantum ether" and influence the propagation of the entangled photons in the Vienna experiment? It's kind of like the idea of frame dragging in general relativity, where the rotation of a massive object affects the surrounding spacetime geometry.

Of course, this is just speculation, and any theory involving an ether-like concept would need to be consistent with all the experimental evidence supporting relativity and quantum mechanics. But I think it's still worth exploring these ideas, as they could lead to new insights into the nature of space, time, and gravity.

The ether was considered to be the physical medium in which light waves propagate, much like air is the medium in which sound waves propagates. The Michelson-Morley experiment (and its successors) proved that it can't be a stationary medium - it would have to move together with the Earth; other experiments had proved that the Earth can't have a very powerful "drag" effect on it either. So, it isn't stationary and it isn't being dragged along with the Earth's movements - almost a contradiction.

Special relativity came along and basically gave an explanation of the workings and movement of light that simply didn't need to make any assumptions about the medium in which light waves propagate. The photoelectric effect, showing that light has a dual nature, either particle or wave, pushed the need for an aether to carry it even lower down. QM probably sealed that completely, with the Schrodinger equation as an explanation of the wave-like nature of fundamental particles.

I really don't think that this interaction between the spin of the Earth and the properties of photons has any true relationship with the notion of an aether. If you wanted to, it would be easier to call the fields in QFT as a kind of aether, I believe they share more properties with the concept.

Experiments show that drag coefficient for light depends on light frequency, but light is not a plain radiowave, it's a Hopfion or a similar thing, so our intuition about its interaction with physical vacuum (ether) can be wrong. Moreover, light is an electromagnetic wave, so it propagates through physical vacuum (ether) because of non-zero capacitance and inductance of the medium. It's possible that light interacts with physical vacuum (ether) only when transitioning from one state to another OR when it is in one of two states, which explains the behavior.

PS.

For example, look at walking droplet. It interacts with the medium through it pilot wave when it bounces off, part of the time, so drag is partial and depends on frequency too.

Frank Wilczek has argued for something similar to this point of view. Here's a non-technical 'op-ed' where he discusses it:

https://drive.google.com/file/d/0B7pl5V0YU9taaXE0ZWJNRzlHNlU...

If there were any kind of ether it would perhaps allow a universal positioning system, basically 3D GPS without supporting infrastructure that worked no matter where you went as long as the system could track you and periodically recalibrate itself vs some landmark. The more sensitive and precise the less recalibration it would ever need.

Yes and no. We can measure our speed and direction of movement against the cosmic microwave background, which averages over a much larger area than our visible Universe (if redshift is interpreted as light aging because of ether), but local measurements will be sensitive to local flow only. It's like measuring speed of wind to calculate position. It's possible, to some degree, if you have a map of winds, but its precision is extremely low.

I think the ether can be seen as a very primitive form of quantum field theory. It's like Newton attempting to do alchemy by turning lead into gold. We later find out that it is possible but not the way he was doing it and tremendously difficult.

But we don't know if ether or QFT or any of these theories is actually what's going on.

Ether is a physical thing, while quantum field is a mathematical model of the physical thing. Don't mix physics and mathematics, please.

Nothing in quantum theory is understood at a level where we can say "this is a physical thing" vs "this is a mathematical abstraction of the physical thing", like we can say for classical physics. In classical physics, it's easy to say "masses and speeds and positions and forces are physical things, while energy or the Langrangian or the Hamiltonian are mathematical tools".

But in quantum physics, we have things like the Schrodinger equation (or the QFTs) where it's not clear. They don't appear to be physical, but we also have the Bell inequalities that suggest there can't be an objective physical layer beneath them either, so we are left with a conundrum.

I think a lot of people do believe that quantum fields are real physical things, and actually "more real" than the classical intuitions we have. In this view, the electron field or the electric field are what actually exists, and balls or water or ether are the abstractions.

Yes, this is the problem I'm talking about. We are not understanding physics at quantum level, so we are using mathematical model to describe reality, but it creates problem when we are starting to understand the physics.

Hydrodynamic quantum analogs are macroscopic objects with quantum behavior, which we can study. We can clearly see, with our own eyes, medium, particle, it pilot wave, and their interaction. For example, double slit experiment is not a mystery anymore: it just self-interference of pilot wave.

I know about the hydrodynamic analogues, and I've seen the double-slit experiment with the bouncing droplet. However, it is unfortunately not a very good model, as it requires changes in the wave to propagate at infinite speed in order to explain other experiments (the ones that fail Bell's inequalities). And that in turn causes many other problems as well. Not to mention, the pilot wave interpretation actually needs lots of work that no one has done yet to actually concur with QFT and the extraordinarily precise experiments that have confirmed the results there. So, it's a particularly problematic interpretation of quantum mechanics, despite having the neat hydrodynamic model.

Hydrodynamic model is not an interpretation or a theory - it's a model. Models are not perfect, but they are physical, they are real things in the real world, no need to prove anything, because they are the proof.

HQM exists, it demonstrates quantum behavior, it has the pilot wave. If QFT doesn't fit the real world, then it is bad for theory, not for the real world.

The hydrodynamic analogue of quantum mechanics has some behaviors of QM, but not all. It's a nice analogy, and it is a real physical system of course, but it is not how elementary particles behave.

If you construct a hydrodynamic experiment where two droplets are bounced on the same wave in different directions (analogous to two entangled particles moving in different directions), and then performed simultaneous measurements on them far away from each other, you would not see the same correlations between the measurements on the separate droplets that you see when doing this experiment with entangled particles.

However, if you perform your measurement on one side, and after enough time on the other, you would see the expected correlation: the measurement on droplet A modifies the pilot wave, and that modification is carried over to affect the behavior of droplet B after some time. In experiments on elementary particles though, this time is 0, or at least much less than distance/c, which is why we say that QM pilot wave theory is non-local.

> If you construct a hydrodynamic experiment where two droplets are bounced on the same wave in different directions (analogous to two entangled particles moving in different directions), and then performed simultaneous measurements on them far away from each other, you would not see the same correlations between the measurements on the separate droplets that you see when doing this experiment with entangled particles

Why not? And what "measurement" means for walking droplets, when we can see the whole situation just by looking at it?

Measurement means the same thing in classical and quantum mechanics: you interact with the system using a measurement apparatus. For the particular experiment I'm thinking of, you'd have to interact with the bouncing droplets to measure some property that is shared by both through their common pilot wave. Most likely this should be something like adding a wave filter and seeing if the droplet is dissolved or not, similar to a polarization filter for light. The key is to perform the two measurements in a way that should show some correlation, such as checking for polarization under non-orthogonal angles.

The reason why I'm certain that this experiment will not reproduce the quantum effect, even though I didn't perform it, is that classical wave polarization is a local phenomenon, it propagates at the speed of light (or much slower) from the location where the polarizer is added. Conversely, the kinds of correlations that have been observed between entangled particles are non-local: they can't be explained by the two particles exchanging information at speeds lower or equal to the speed of light. This is well established in experiments related to Bell's inequality. It is also well established in experiments that this doesn't hold true for classical systems.

I'm scratching my head about how to reproduce Bell inequality in macro, to see what's going on...

It's not very hard to perform Bell test-style experiments with macroscopic objects, the problem is that the Bell inequality actually holds for them. Many classical physics phenomena produce pairs of objects whose properties must be shared, analogous to quantum entanglement.

In fact, the inequality in Bell's theorem is based exactly on how classical statistics works: if you and I randomly choose to measure some aspect of each of a pair of "entangled" objects, and assuming the result of our measurement can only be +1 or -1, then on average the sum of our measurements will be less than or equal to 2. It turns out though that this logic doesn't work for entangled quantum objects.

And one small note here: based on everything we know, the key here is quantum entanglement, not scale. That is, if you could entangle two basketballs or planets for long enough to perform a Bell test on them, they would likely reproduce the particle results. However, this property of quantum systems is very hard to preserve for such a large system with so many ways of interacting with the environment and experiencing decoherence.

The problem with walking droplet is that they have no polarization. However, we can use a pair of walkers, which walk together, to try to see how they walk through a line of pillars at different angles. It should work and produce similar results to results produced by polarized filters with light.

Maybe, it will be possible to make two entangled pairs of walkers and then see what happens to them.

Aren't the waves in the walking droplet experiment transverse waves, that do have polarization? Polarization is a property of waves, not particles.

This is a really great experiment. It's nice to see real work being done on the ground with these kinds of tests and write-ups. I am not a physicist but I imagine this could have implications for gravitational wave detection by improving LIGO's optical sensors, maybe optical sensors in general?

Or maybe this could help with tracking time more accurately? Hopefully someone with knowledge can chime in with what this means in practice.

I don't believe the LIGO experiment is utilizing entangled photons. This experiment is using a very different type of interferometer because they're trying to be sensitive to rotations, whereas LIGO's interferometer is for measuring changes in length. LIGO's biggest problem is how to minimize losses in their mirrors.

LIGO could potentially utilise EPR entanglement between photons in different parts of the detector but it does not do so yet. That’s a potential future development. It does use quantum squeezing though

https://www.science.org/doi/10.1126/sciadv.ado0215

Why would the earths rotation be more significant influence on particles versus its orbit or the solar systems movement around the galactic core, the galaxy's movement, etc? Or do they all, but are unaccounted for in this experiment maybe?

1/day ~ 1,16e-5 Hz

1/year ~ 3,17e-8 Hz

1/230 million years ~ 1,38e-16 Hz

From this perspective, the next effect that might be relevant is the moons orbit, which should be at a frequency 1.5 orders of magnitude below the Earth spin.

Yeah, but for that to be relevant you'd have to set up the experiment on the moon :D

I’m not sure how interesting this is - of course rotation causes the paths to differ and become measurable.

I’ve been wondering about sending photons away from earth and having their paths bend due to gravity (and later have them interfere). That would be interesting because GR would be involved.

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