I Applications for negative radiation pressure?

[JD23]

TL;DR Summary

Can we pull with waves? Which ones and how? Applications?

There are a few articles about negative radiation pressure - in theory allowing to pull e.g. solitons: https://scholar.google.pl/scholar?q=negative+radiation+pressure
The articles suggests realization in graphene - could it work?
Could there be different realizations, like negative radiation pressure with EM waves, photons using something like laser?
If so, what applications could it allow for?
There are optical tweezers ( https://en.wikipedia.org/wiki/Optical_tweezers ) allowing to move objects - is it related?

ps. In https://en.wikipedia.org/wiki/Radia...sure_from_momentum_of_an_electromagnetic_wave
radiation pressure is <E x H>/c - it doesn't seem to require being positive?

 

[JD23]

Just found "Macroscopic laser pulling based on the Knudsen force in rarefied gas " article with lots of examples of pulling with photons: https://opg.optica.org/oe/fulltext.cfm?uri=oe-31-2-2665&id=525052

About 10 years ago, optical pulling force (i.e. optical tractor beam) emerged [10–12] as an attractive and popular concept, not only because the counterintuitive feature but also the profound mechanism underneath and promising applications. In the recent several years, a variety of optical pulling schemes have been proposed mainly based on the physics of momentum transfer and energy transfer. On the one hand, as for the momentum transfer path, Bessel beams were proposed to pull elongated objects [13] and core–shell structures [14,15]. Fernandes et. al. reported an optical pulling using chiral light [16]. Enhancement of optical pulling force was reported using optically bound structures [17]. Optical pulling in a periodic photonic crystal background was reported, which was originated from the self-induced backaction of the object to the self-collimation mode [18]. Long-range optical pulling of nanoparticle based on Bessel beam was achieve by simultaneously using several novel and compatible mechanisms [19]. Optical pulling mechanism via engineering the topology of light momentum in the background was also reported [20]. Besides, optical pulling can be also realized using the fluidic drag force and metamaterials (the so called “meta-tweezers”) that have provided numerous opportunities in compact multifunctional optical manipulations, such as trapping, transporting, sorting and imaging [21,22]. On the other hand, optical pulling based on photon energy transfer also appear with the assistance of surrounding medium including gas and liquid, in which the photophoresis induced optical pulling is a significant scheme. Photophoretic force discovered by Ehrenhaft has been widely used in optical manipulation [4,23,24]. When an absorptive object is irradiated by inhomogeneous light, asymmetrical temperature distribution is created, and then hot side will give a larger recoiling force than the cold side originated from the thermal motion of medium molecules. In rough comparison, the Photophoretic force imparted by the gas molecules is c/3υ times greater than the radiation pressure originated from the photon momentum transfer, where c is the speed of light and υ is the gas molecular velocity [25]. Shvedov et. al. achieved long-range polarization-controlled laser pulling of gold-coated hollow glass spheres [26]. Zhang et. al. demonstrated a new principle of the laser-induced hammer-hit vibration of a micron-sized black sphere in liquid glycerol [27]. Lu et. al. reported light-induced pulling and pushing of micro gold plate by the synergic effect of optical force and photophoretic force [28]. Up to now, based on the physics of momentum transfer and energy transfer, various optical pulling of small objects at the micro-nano scale have been demonstrated. However, optical pulling of a macroscopic object is challenging and is rarely reported.

 

[sophiecentaur]

TL;DR Summary: Can we pull with waves? Which ones and how? Applications?

electromagnetic_wave
radiation pressure is <E x H>/c - it doesn't seem to require being positive?

It's a very attractive (no pun intended) idea but . . . .

From what's in your references, the effect is 1. Restricted to nanoscale particles and 2. Involves more than one 'beam' so is the intuitive picture of the Poynting vector relevant?

It doesn't imply that the Klingon ship could actually grab us.

 

[JD23]

Indeed, while there are various approaches, it seems to be restricted to microscopic objects.

Personally I am more interested in even smaller objects - if we could "pull photons" with some negative photon pressure?
E.g. using ring laser like below - it allows for nearly unidirectional photon trajectories, from perspective after CPT symmetry this direction would be reversed - "pushing photons" to the target on the left, what without CPT suggests pulling photons from it (?)
From equations perspective ( https://en.wikipedia.org/wiki/Stimulated_emission#Mathematical_model ), the absorption equation acts on the central target, but also the target on the right (behind right mirror) - so shouldn't the emission equation also act on the target on the left (behind left mirror)?
It would require initial excitation of this target: N_2>0, e.g. as a lamp.

 

[JD23]

As optical pulling allows to pull e.g. in optical tweezers, negative radiation pressure to pull solitons - maybe we could pull photons?
One of application direction might be 2WQC (two-way quantum computers) attempting to solve NP problems (standard 1WQC might be bounded with e.g. Shor, Grover).

I would gladly discuss and generally am searching for collaboration in these topics, especially access to ring laser to test if it allows for negative photon pressure, what is required e.g. by CPT symmetry.

View attachment 329229

 

[sophiecentaur]

if we could "pull photons" with some negative photon pressure?

Is there any example of photon - photon interaction?

This wold be quite different from an interaction between a charged mass.

 

[JD23]

Here I thought as positive-negative photon pressure, like in stimulated emission-absorption: https://en.wikipedia.org/wiki/Stimulated_emission#Mathematical_model
As one allows for quantum computer state preparation, shouldn't the second allow for its CPT analogue?

From photon-photon interaction there can be e.g. pair production: https://en.wikipedia.org/wiki/Pair_production
https://newscenter.lbl.gov/2020/09/23/lhc-creates-matter-from-light/

 

[sophiecentaur]

Those links are all about photon - matter interaction.
Photons are Bosons which are not subject to the Pauli Exclusion Principle so where would photons become entangled?

 

[JD23]

Pair creation is about creation of e.g. electron+positron pair from pair of photons, here if running backward you get its analogue for 1D topological defects: https://en.wikipedia.org/wiki/Topological_defect

Production of entangled photons is made e.g. using SPDC crystals or a few new ways on photonic chips - see e.g. https://www.nature.com/articles/s41534-020-0263-7

 

[JD23]

Existence of optical pulling, negative radiation pressure, brings question about its applications for computational purposes.

For electronic or microfluidic chip we can actively influence them from both directions: both pushing into a chip, and pulling from for better flow control - could it be done for mathematically similar: EM, photonic? - also pull with negative radiation pressure?

E.g. ring laser allows for unidirectional photon trajectories, from perspective of CPT symmetry it would create positive radiation pressure toward minus time - suggesting negative pressure toward plus time (?)

EM-hydro analogy table is from here: https://www.researchgate.net/public...gy_between_electromagnetism_and_hydrodynamics

 

[Drakkith]

For electronic or microfluidic chip we can actively influence them from both directions: both pushing into a chip, and pulling from for better flow control - could it be done for mathematically similar: EM, photonic? - also pull with negative radiation pressure?

Probably not. Photon-photon interaction is virtually non-existent except at extremely high intensity and energy.

E.g. ring laser allows for unidirectional photon trajectories, from perspective of CPT symmetry it would create positive radiation pressure toward minus time - suggesting negative pressure toward plus time (?)

Pressure on what and where? Why do we even need to talk about CPT symmetry?

 

[Vanadium 50]

This looks needlessly over-complicated. The question seems to boil down to "can a beam of light carry momentum opposite to its direction of motion?" which has a clear answer - "no".

 

[JD23]

This analogy focuses on radiation pressure - being able to do it for e.g. for hydrodynamics, which especially for superfluids (no viscosity, entropy growth) uses nearly the same hyperbolic PDEs.
Claiming it is impossible for EM waves, photons, one needs to point the difference - what equation difference forbids this analogy?

The main difficulty seems being able to realize a pump for EM waves, photons.
While there should exist various ways as for optical pulling, negative radiation pressure, I think ring laser (unidirectional: with optical isolator) should already allow for that.

The main argument uses CPT theorem - that from perspective with applied CPT symmetry, physics should work the same - especially if avoiding asymmetric processes like entropy growth.
So looking at above diagram from CPT symmetry perspective, unidirectional photon trajectories of ring laser would be reversed - it would push photons into the chip from the opposite side, what in standard perspective (no CPT) means pulling photons from the chip (positive <-CPT-> negative radiation pressure).

From perspective of stimulated emission/absorption equations ( https://en.wikipedia.org/wiki/Stimulated_emission#Mathematical_model ), in CPT symmetry perspective they are switched - hence B_12 = B_21 Einstein's coefficients have to be equal.
We assume both these equations act on the laser crystal inside, but additionally target on the right absorbs produced photons as in absorption equation on the right.
From perspective of CPT symmetry, photon trajectories would be reversed - hence target on the left should absorb photons accordingly to equation on the rights, what means acting of equations on the left in standard perspective (no CPT).

 

[Drakkith]

Claiming it is impossible for EM waves, photons, one needs to point the difference - what equation difference forbids this analogy?

No one said anything about an analogy. You can use whatever analogy you want as long as you remember that it's just an analogy and can only taken so far before it starts to fall apart.

The main argument uses CPT theorem - that from perspective with applied CPT symmetry, physics should work the same - especially if avoiding asymmetric processes like entropy growth.
So looking at above diagram from CPT symmetry perspective, unidirectional photon trajectories of ring laser would be reversed - it would push photons into the chip from the opposite side, what in standard perspective (no CPT) means pulling photons from the chip (positive <-CPT-> negative radiation pressure).

I'm no expert in CPT symmetry, but I'm not convinced this is accurate. A 'mirror image' of this setup would have the positions of everything mirrored too, correct? Which would seem to be required if the evolution of the system is to be identical to the evolution of the original system. Thus the photons would not be 'pulled' from the chip in either system.

 

[JD23]

Regarding analogies, having two situations governed by the same equations, recreating scenarios between them you should get the same behavior.

Regarding CPT symmetry, physicists believe it is satisfied: https://en.wikipedia.org/wiki/CPT_symmetry
"The CPT theorem says that CPT symmetry holds for all physical phenomena"
the diagrams for simplicity use only time symmetry - formally there is also applied P and C.

While in standard view ring laser in diagram hits the photonic chip, in perspective of CPT symmetry there is additional beam of photons in the opposite direction: hitting CPT(photonic chip) with positive radiation pressure toward minus time, what means negative radiation pressure toward plus time.

Below is example of such photonic chip from https://www.nature.com/articles/s41467-019-11489-y - in which laser pulse acts as state preparation influencing the initial state.
In CPT symmetry perspective there is similar laser pulse for state preparation of CPT(photonic chip) - influencing its initial state, which is the final state of photonic chip.
If being able to influence the final state, we could attack postBQP problems e.g. NP replacing postselection with physical constraints - in theory could build much more powerful quantum computers.

 

[Drakkith]

While in standard view ring laser in diagram hits the photonic chip, in perspective of CPT symmetry there is additional beam of photons in the opposite direction: hitting CPT(photonic chip) with positive radiation pressure toward minus time, what means negative radiation pressure toward plus time.

I don't think this is the case. The photons should not be going from the chip to the laser. Such a system would not evolved identically with its non-mirrored system, which is the whole point of CPT symmetry if I understand it correctly.

 

[JD23]

Looking at this system from perspective of CPT symmetry, photon trajectories would be reversed - ring laser would still send photons, but in the opposite direction.
The situation seems exactly as in hydrodynamics, also symmetric - reversing the flow in time/CPT symmetry perspective.
They use active pump - requiring additional energy source, there is no violation of e.g. 2nd law of thermodynamics.

While naively radiation pressure seems only positive, it is a vector <E x H>/c ( https://en.wikipedia.org/wiki/Radia...sure_from_momentum_of_an_electromagnetic_wave ): can be toward a surface (positive, pushing), or outward (negative, pulling) ... time symmetry perspective reverses direction of forces, pressures.
https://scholar.google.pl/scholar?q=negative+radiation+pressure
https://scholar.google.pl/scholar?q=optical+pulling

 

[Drakkith]

They use active pump

Who or what is 'they' and what pump are you referring to?

While naively radiation pressure seems only positive, it is a vector <E x H>/c ( https://en.wikipedia.org/wiki/Radia...sure_from_momentum_of_an_electromagnetic_wave ): can be toward a surface (positive, pushing), or outward (negative, pulling)

Sure. But I don't feel your CPT argument supports your claim. I still think that you have to mirror your physical setup. But, again, I'm not an expert in this area, so I could be entirely mistaken.

 

[JD23]

"They" as the electric, hydrodynamical, and hypothetical photonic circuits from #10 post above we are discussing - simplified below.

Regarding CPT theorem, it says that looking from perspective with applied this symmetry, the equations of physics are the same.
There are obvious differences like 2nd law of thermodynamics, but they cannot be inside some fundamental equations e.g. of Standard Model.
Instead, they have to be a property of concrete solution we live in - like throwing a rock into symmetric surface of a lake, for 2nd law such "rock" was e.g. Big Bang: when everything was localized, hence entropy was low, creating its gradient we observe.

Ring laser shoots photons in one direction.
Looking at it from perspective of CPT symmetry physics, photon trajectory would be reversed - it should still shoot photons, but into the opposite side of the CPT(photonic chip) ... exactly as in hydrodynamical analog, governed by practically the same equations (especially if using superfluid: no viscosity, entropy growth).

Below is the simplest case: instead of a chip, just use a split - for electrons or fluid it is obvious that flow down the split should be reduced due to also pulling.
One of the simplest experimental test is if we could also do it with photons - if additional negative radiation pressure could reduce flow down the beamsplitter?

 

[Drakkith]

I can barely make heads or tails out of your diagrams. What is the difference between the 2 optical 'circuits' on the right other than the direction of the photons being opposite? What is the beam splitter even doing? What does 'no photon source' mean exactly? Where is this negative pressure coming from? Are the two 'circuits' connected, or are you just showing two different setups?

 

[JD23]

The difference between the blue and violet background setting, is looking at it from standard perspective and with applied CPT - for simplicity there is shown only time symmetry.

CPT theorem says both are governed by the same equations of physics - so in both perspectives ring laser should produce photons, but in the opposite directions.

If the number of photons produced in both perspectives would be the same, then all should go straight through the beamsplitter - similar balance argument suggests in electronic and hydrodynamical analogs the flow down the split should be zero.

 

[Drakkith]

If the number of photons produced in both perspectives would be the same, then all should go straight through the beamsplitter - similar balance argument suggests in electronic and hydrodynamical analogs the flow down the split should be zero.

What's on the other side of the beamsplitter in each setup? Again, are these two separate setups, or are you connecting them?

 

[JD23]

This is the same setup, only viewed from two perspectives: standard and with applied time/CPT symmetry.

Indeed the question what is up/down the beamsplitter is a very important one - e.g. in CPT perspective for photons to go up the beamplitter, in normal perspective would require a photon source there.

So if there are no additional photon sources, e.g. only detectors, it seems photons should go straight through the beamsplitter (?)

ps. Nice related experiment from Vaidman group: literally "Asking photons where they have been": https://physics.aps.org/featured-article-pdf/10.1103/PhysRevLett.111.240402 - turns out light has visited exactly the mirrors seen for propagation in both time directions (also A and B in case (b)):

 

[Drakkith]

This is the same setup, only viewed from two perspectives: standard and with applied time/CPT symmetry.

Okay. You have a setup which works one way normally and apparently works a different way under CPT reversal.

Indeed the question what is up/down the beamsplitter is a very important one - e.g. in CPT perspective for photons to go up the beamplitter, in normal perspective would require a photon source.

So if there are no additional photon sources, e.g. only detectors, it seems photons should go straight through the beamsplitter (?)

What does "go straight through the beamsplitter" mean? I don't think the beam splitter even works as intended if you change the direction the photons are going. They'll reflect upwards instead of downwards, missing whatever you had the split beam going into. Note that by reflecting upwards, the photons are just lost. You don't have anything coming up into the beam splitter to trace the reverse path the split photons from the original setup take.

 

[Vanadium 50]

This still looks needlessly over-complicated. Pressure is proportional to energy density, which is itself proportional to E² + B². Not the squares, his is negative for no values of E and B.

If you have a more complicated analysis that gives another answer, there must be an error in it somewhere, jsut as one thinks they have found a perpetual motion machine, there must be an error in it somewhere.

 

[JD23]

Okay. You have a setup which works one way normally and apparently works a different way under CPT reversal.

It is the exactly the same system - just viewed from different perspectives.
E.g. the same circulating electrons/fluid/photons, but in the opposite directions - looking from our perspective and with applied time/CPT symmetry ... like switching pump to opposite direction.

For example quantum computers use unitary/reversible gates - which can viewed from both time directions (avoid asymmetry like entropy growth, also superfluids).
However, their boundary conditions are treated in asymmetric way - it is believed that we can only affect the initial state by state preparation.
If being able to do "the same as state preparation but reversed": realize its CPT symmetry analog (e.g. pull-push, negative-positive pressure, stimulated emission-absorption), then we should be able to also affect the final state - build much more powerful quantum computers (attacking postBQP).

What does "go straight through the beamsplitter" mean?

If in both perspectives (with/without CPT) the ring laser produces the same amount of photons, it would mean that they have to "go straight through the beamsplitter" - instead of "turning" up or down.
The same as for e.g. electron current or fluid - first Kirchhoff law, conservation law say there can be no flow down the split.

Pressure is proportional to energy density

It is entire vector: <ExH>/c - can be positive: toward surface, or negative: outward ... CPT symmetry changes sings of forces, and so also of pressures.
https://en.wikipedia.org/wiki/Radia...sure_from_momentum_of_an_electromagnetic_wave

 

[Drakkith]

It is the exactly the same system - just viewed from different perspectives.

Then why does it work differently in each perspective? Let's look at a simpler setup. Just a single laser shining to the right into a wall. Your version of CPT reversal would simply reverse the direction of the light, making the wall emit light and the laser collect it. That doesn't seem right.

If in both perspectives (with/without CPT) the ring laser produces the same amount of photons, it would mean that they have to "go straight through the beamsplitter" - instead of "turning" up or down.

I'm not sure what you mean. In both cases the beam splitter is reflecting part of the beam, just in different directions (up vs down). I assumed you had something attached to the bottom of the beam splitter, hence why I was saying I didn't think it would work correctly under your CPT reversal since the photons would be reflected the wrong way.

 

[Vanadium 50]

Again, this is overcomplicating things. T reverse a laser and you have a coherent beam entering the laser and then optically pumping the medium.

No different than a broken vase reassembling itself when T reversed. It's not impossible, but requires a spontaneous reduction in entropy. It doesn't violate any laws, it just doesn't happen.

It absolutely does not mean that you can make tractor beams out of lasers.

 

[JD23]

Then why does it work differently in each perspective? Let's look at a simpler setup. Just a single laser shining to the right into a wall. Your version of CPT reversal would simply reverse the direction of the light, making the wall emit light and the laser collect it. That doesn't seem right.

It has to work the same from all perspectives, and does in diagrams I have shown - e.g. inverting direction of circulation in all 3 settings (electronic, hydrodynamic, photonic).
There is asymmetric: spontaneous emission, because of asymmetry of solution we live in: it is easy for photons to escape toward future, but it is difficult to find its source in the past - as in your shining a wall example.
But there are also symmetric: stimulated emission-absorption (e.g. in used ring laser), two equations which switch in CPT symmetry perspective, hence have to be governed by the same Einstein coefficient: B_12 = B_21.

I'm not sure what you mean. In both cases the beam splitter is reflecting part of the beam, just in different directions (up vs down). I assumed you had something attached to the bottom of the beam splitter, hence why I was saying I didn't think it would work correctly under your CPT reversal since the photons would be reflected the wrong way.

For symmetric construction of ring laser, it should produce the same amount of photons in both perspectives (with/without CPT) - what would require that all of them go straight through the beamplitter (without other photon sources).
Analogously to e.g. battery absorbing the same amount of electrons as producing, pump sending out the same amount of fluid as taking in.
Laser requires some initial pumping e.g. using spontaneous emission of some external source, but then for perfect circulation there would be only symmetric: stimulated emission-absorption.

It absolutely does not mean that you can make tractor beams out of lasers.

Optical tweezers, optical pulling are going toward a "tractor beam".
https://en.wikipedia.org/wiki/Optical_tweezers
https://scholar.google.pl/scholar?q=optical+pulling
e.g. from: https://www.semanticscholar.org/pap...gsen/b3d4e9ac17370604b83ca88c451f50d5711543ef

 

[Drakkith]

It has to work the same from all perspectives, and does in diagrams I have shown

No it doesn't. The beam splitter reflects photons one way in one 'perspective' and another way in the other perspective. I believe you need to do a parity reversal with your setup if you want to preserve the direction the photons are reflected. That is, flip the sign of one or more of the spatial coordinates of each point in your setup.

For symmetric construction of ring laser, it should produce the same amount of photons in both perspectives (with/without CPT) - what would require that all of them go straight through the beamplitter (without other photon sources).

I don't follow you. If the beam splitter reflects half of the incident light then both perspectives should lose half their light, unless beam splitters only work one way. I confess that I don't know if they do. Assuming they do work the same no matter which side the light enters, then it looks to me like you get identical beam intensities in both perspectives.

Also, you keep talking about CPT symmetry, but it isn't entirely clear which reversals/inversions you are actually doing.

 

[JD23]

If the beam splitter reflects half of the incident light then both perspectives should lose half their light, unless beam splitters only work one way.

Exactly - that's my point: if in both perspectives symmetric ring laser would produce the same amount of photons (and there are no other sources), the fact that they are the same system requires that "photons go straight through beamsplitter" - cannot turn up/down.
In electric/hydro analogs, going down the split is directly prevented by negative pressure - suggesting analogous explanation for beam-splitter ... it would be great to perform such a test, but it needs some photonic lab (I don't have access to) ...

Also, you keep talking about CPT symmetry, but it isn't entirely clear which reversals/inversions you are actually doing.

I am talking about CPT because T alone is not conserved.
For simplicity I use T alone in diagrams, but formally imagine there is also CP.

 

[Vanadium 50]

I am talking about CPT because T alone is not conserved.

It is in the electromagnetic interaction.

 

[JD23]

I wanted to add it ... but to get unidirectional photon trajectories there is used Faraday effect, which violates T.

It rotates linear polarization by a fixed angle, due to difference of propagation speeds of two circular polarizations - which are switched in T symmetry.

 

[Vanadium 50]

Faraday effect, which violates T.

No it does not. (A common error is to ignore the effect of T on the magnetic field)

 

[PeterDonis]

here if running backward you get its analogue for 1D topological defects

I don't know where you're getting this from. The CPT inverse of pair creation is pair annihilation: an electron and positron annihilate and a pair of photons comes out.

 

[PeterDonis]

@JD23 where are all these diagrams in your posts coming from?

 

[PeterDonis]

I would gladly discuss and generally am searching for collaboration in these topics, especially access to ring laser to test

PF is not for discussing or pursuing personal research.

 

[Drakkith]

Exactly - that's my point: if in both perspectives symmetric ring laser would produce the same amount of photons (and there are no other sources), the fact that they are the same system requires that "photons go straight through beamsplitter" - cannot turn up/down.

Obviously such a setup would indeed split the laser beam, so I don't know what to tell you.

 

[JD23]

No it does not. (A common error is to ignore the effect of T on the magnetic field)

I have seen such a statement in a few articles, e.g. "Faraday effect that breaks the time-reversal symmetry" in https://www.nature.com/articles/s41566-018-0127-2 so I assumed it is true ... indeed with some internal conflict I should explore as electromagnetism alone is T symmetric and there is nearly no way to get out of EM here (hyperfine interactions with nucleus?)
Thanks for clarification, I will have to think about it.

Obviously such a setup would indeed split the laser beam, so I don't know what to tell you.

In electronic and hydrodynamic analogs the statistics of split is changed by negative pressure - as equations are nearly the same, why it cannot be still true for split of light analog by negative radiation pressure?
CPT theorem suggests it should work, it would be great to test it experimentally ...

Regarding the diagrams, some are linked articles, some I have made for potential computational applications of negative radiation pressure this thread is about.

 

[Drakkith]

In electronic and hydrodynamic analogs the statistics of split is changed by negative pressure - as equations are nearly the same, why it cannot be still true for split of light analog by negative radiation pressure?
CPT theorem suggests it should work, it would be great to test it experimentally ...

As has been said already, light doesn't interact with itself hardly at all. As far as the light is concerned, there is no radiation pressure at all on itself. This is unlike physical flows like water or electric current where the flow is highly interacting with itself.

 

[JD23]

But thinking about EM waves not individual photons, the equations are practically the same as for superfluids - what would prevent recreation of such circulation with active pump?
Negative radiation pressure and optical pulling exist both theoretically and experimentally - claiming impossibility requires a different argument.

So what about intermediate picture - microwaves in waveguides?
Would such EM wave be mathematically very different from superfluid?
Searching "microwave Farday effect" there are a few articles - so enforcing unidirectional circulation might be doable (?)
Would it be possible to build circulation with active pump for wicrowaves?
If so, could split behavior be controlled also by negative (radiation) pressure like in hydrodynamical analog?
If so, what would change for optical photons - of shorter wavelengths?

Ps. Some waveguides from https://www.testandmeasurementtips.com/basics-waveguides-microwaves-ovens/

 

[Drakkith]

But thinking about EM waves not individual photons

Irrelevant. Light does not interact with itself enough either way you look at it.

the equations are practically the same as for superfluids

Again, irrelevant.

So what about intermediate picture - microwaves in waveguides?
Would such EM wave be mathematically very different from superfluid?

That depends entirely on what you mean by 'very different'. And on how deep you look into things.

If so, could split behavior be controlled also by negative (radiation) pressure like in hydrodynamical analog?

No. Radiation pressure acts on matter, not on light.

 

[JD23]

Pressure is effective description of hidden dynamics, e.g. <E x H>/c averaged vector for radiation - so how does this dynamics differ between superfluid and electromagnetism to prevent recreation of circulation with pump?
Please point this difference in equations governing them.

Here are lots of articles about this analogy:
https://scholar.google.pl/scholar?q=electrodynamics+hydrodynamics+analogy

ps. Related: video of Casimir effect for waves in water - this time pulling taken in the opposite direction of this analogy:

 

[Drakkith]

Pressure is effective description of hidden dynamics, e.g. <E x H>/c averaged vector for radiation - so how this dynamics differs between superfluid and electromagnetism to prevent recreation of circulation with pump?

Enough with the analogies. Either talk specifically about your optical setup, using optical terminology, or I will lock this thread. Things like 'recreation of circulation with pump' add an unnecessary step that we have to work through to get to what you're actually wanting to know.

 

[JD23]

I have shown the setting in #10 and #19 here, and we have discussed that e.g. CPT theorem suggests such setting should work similarly in all: electronic, hydrodynamic ... so why not for e.g. EM microwaves, photons?
I agree that negative radiation pressure feels non-intuitive, but it doesn't make it nonexistant, for what I still haven't seen meritorious counterargument.

Ok, so let us skip this potential computation application direction, and leave this thread for different aspects of "Negative radiation pressure" as in the title (please don't lock it).

 

[Drakkith]

I agree that negative radiation pressure feels non-intuitive, but it doesn't make it nonexistant, for what I still haven't seen meritorious counterargument.

I don't think anyone here is claiming that negative radiation pressure doesn't exist (see here). We're saying that your setup probably doesn't do what you think it does.

I have shown the setting in #10 and #19 here, and we have discussed that e.g. CPT theorem suggests such setting should work similarly in all settings: electronic, hydrodynamic ... so why not for e.g. EM microwaves, photons?

Again, I don't see any need to invoke CPT symmetry. If you provide an optical setup, it should immediately be clear what it does. Your setups provided so far do nothing exceptional. You have a ring laser and a beam splitter that splits the beam. That's it. It's a very simple setup.

 

[JD23]

Beside EM-hydro analogy, the only argument I have is that looking from CPT symmetry perspective, symmetric ring laser should produce the same amount of photons in the opposite direction.
If so, just counting the photons, without other sources, photons would have to go "straight through the beamsplitter" (analogously to straight through the split in electric, hydro settings due to negative radiation pressure).
In both perspectives this is practically the same setting, hence should work the same.

I understand that beamsplitters are made to have fixed proportions e.g. 50:50 (for e.g. laser beam carrying positive radiation pressure).
But was it tested in the presence of negative radiation pressure? (a very subtle condition, opposite to positive)
If it wasn't and there are arguments it might be affected, maybe it is worth experimental verification.

Probably it would not be affected as nearly everybody expects, but it would bring questions:
- what is wrong with the above CPT symmetry-based argument?
- what is the mathematical difference between EM and superfluid allowing circuit with pump for exactly one of them?

 

[Drakkith]

Beside EM-hydro analogy, the only argument I have is that looking from CPT symmetry perspective, symmetric ring laser should produce the same amount of photons in the opposite direction.

By itself it might, but you have other things in the system.

In both perspectives this is practically the same setting, hence should work the same.

But that's the thing. It's not the same setting. The beam splitter is at a different angle relative to the oncoming beam of light in the second setup.

I understand that beamsplitters are made to have fixed proportions e.g. 50:50 (for e.g. laser beam carrying positive radiation pressure).
But was it tested in the presence of negative radiation pressure?

There is no negative radiation pressure in any of your setups and negative pressure appears to only be possible in certain types of materials.

- what is wrong with the above CPT symmetry-based argument?

I think you've forgotten the P in CPT. A parity transform of the system would appear to solve the issues I've brought up.

- what is the mathematical difference between EM and superfluid allowing circuit with pump for exactly one of them?

A great many things. Light can't stop moving, for example. It doesn't interact with itself hardly at all. It's uncharged. It's massless. It's fundamentally different from any superfluid.

 

[JD23]

By itself it might, but you have other things in the system.

But that's the thing. It's not the same setting. The beam splitter is at a different angle relative to the oncoming beam of light in the second setup.

Not having other photon sources, to make it more symmetric we can rotate the beamplitter 90 degrees toward us (up/down -> to/from us) - this way in both perspectives (with/without CPT) it would be practically the same situation.
In CPT symmetric physics, preparing situation being the same in both perspectives like circulation with pump - shouldn't they differ by just direction of circulation?

A great many things. Light can't stop moving, for example. It doesn't interact with itself hardly at all. It's uncharged. It's massless. It's fundamentally different from any superfluid.

Indeed for optical photons it is less intuitive, so I have suggested intermediate picture: microwaves in waveguides - which is more "pure EM" governed by nearly the same equations as superfluid - would such reduction of flow down the split by negative radiation pressure be possible for microwave setting?

If so, maybe such more powerful quantum computer (attacking postBQP by physical constraints) could be made on microwaves?
... or maybe superfluid quantum computer with mechanical qubits (e.g. https://phys.org/news/2023-06-mechanical-qubits.html ) of fluid vibrations, for which construction of such two-way quantum computer would be just a matter of connecting it into a circuit with pump.

 

[Drakkith]

Not having other photon sources, to make it more symmetric we can rotate the beamplitter 90 degrees toward us (up/down -> to/from us) - this way in both perspectives (with/without CPT) it would be practically the same situation.

The only beam splitters I've seen are cube-like with the internal diagonal joining the two pieces as the reflecting surface. There is no way to orient this such that it will reflect the two beams the same way.

Indeed for optical photons it is less intuitive, so I have suggested intermediate picture: microwaves in waveguides - which is more "pure EM" governed by nearly the same equations as superfluid - would such reduction of flow down the split by negative radiation pressure be possible for microwave setting?

No, not as far as I know.

At this point I feel we're just going in circles. Light doesn't follow the mathematical laws of hydrodynamics or electrical circuits, so continually asking, "why won't this work like the analogy does" is getting us nowhere.

If you can find a legitimate setup that shows negative radiation pressure then we can discuss it. But trying to develop your own based on analogies and a questionable argument using CPT symmetry is not going to fly here at PF. Thread locked.