Duda Jarek

Indeed stimulate the target to emit/deexcite, like pulling photons out of it - suggested by symmetry (T/CPT) ... if possible could lead to lots of new applications, e.g.:

- new calculation possibilities e.g. for quantum computing,

- low probability nuclear transitions - if they produce some characteristic gammas, then they could be stimulated by such caused deexcitation - these high energy photons are available e.g. in free electron lasers, wigglers/undulators in synchrotron ... also in standard laser setting using above Einstein's equation. Which nuclear transitions would be the most interesting, practical?

- similarly for chemistry - probably useful for many technological processes ...

To test application of the emission formula for the target on the left, it needs to be initially excited - e.g. a lamp.

In this case it would deexcite in isotropic way - the question to test is if there is additional deexcitation caused by the laser, what would be seen by detectors around: in this case getting a lower power of light.

The polarization might be interesting to try to use it to stimulate deexcitation of one polarization of atoms, what might allow e.g. for CPT analogue of state preparation for quantum computing.

The basic test is for nonpolarized target: if the formula on the left applies also to the target on the left, as suggested by CPT symmetry switching the targets. The main difficulties of such test is requirement of high N_2/N excited population, and that the asymmetry is imperfect - some percentage of photons travel in the opposite direction, exciting our target.

1 minute ago, swansont said:

The stimulated de-excitation can happen with the laser causing the excitation. It’s why a two-level system can’t have more than 50% of the atoms in an excited state.

And since de-excitation requires that the atom be in an excited state, the situations aren’t the same.

You are writing about the central target (pumped crystal) - to which both equations apply. The question is about the left/right targets - CPT symmetry suggests both should have corresponding formula.

Here is another perspective on the ring laser setting using formulas from https://en.wikipedia.org/wiki/Stimulated_emission

There are two (Einstein's) formulas - for absorption it applies to the central target (pumped crystal), and the standard target on the right.

The symmetric emission formula is considered only for the central target.

However, in perspective after CPT symmetry the targets and equations would switch - hence emission formula should also symmetrically apply to the target on the left - stimulate its deexcitation (if satisfying condition of being excited).

Some potential applications of such suggested by CPT symmetry stimulated deexcitation, intuitively "pulling of photons":

- low probability nuclear transitions - if they produce some characteristic gammas, then they could be stimulated by such caused deexcitation - these high energy photons are available e.g. in free electron lasers, wigglers/undulators in synchrotron ... also in standard laser setting using above Einstein's equation. Which nuclear transitions would be the most interesting, practical?

- similarly for chemistry - probably useful for many technological processes (which ones?).

- maybe stimulated proton decay - ultimate energy source: complete matter -> energy transition, ~100x energy density than fusion from any matter. Violation of baryon number is required e.g. by baryogenesis, Hawking radiation. They cannot observe it in room temperature water, but maybe it is a matter of proper conditions, like pulling photons of characteristic energies by some powerful free electron laser? Could use normal laser setting.

- ?

Deexcitation is time/CPT reversal, analogue of excitation - here caused by the action of laser.

Isn't it lots of microscale tests?

The CPT symmetry seems nonintuitive especially due to time symmetry, e.g. applying it to macroscopic scenario with clear causality, naively it should reverse causality, e.g.:

CPT(laser causes excitation of target) = CPT(laser) causes deexcitation of CPT(target)

microscopically: CPT(stimulated emission) in laser = stimulated absorption

Is it true? If so, it could bring lots of applications, but seems unknown ...

Thanks for the list, so I think we agree CPT should be true also in macroscale - but were there experiments really testing macroscopic CPT?

If not, maybe it is worth to design and conduct such tests - like proposed, using time-asymmetric light sources e.g. ring laser or free electron laser.

The only nonstandard in the discussed setting is being "behind" instead of "in front" of the source of coherent light ... but becoming proper "in front" when looking from perspective after applying CPT symmetry. This way we would ask physics if it works the same after applying CPT.

Microscopically, while e.g. laser cooling is CPT analogue of laser heating, we are asking if there exists CPT analogue of stimulated emission - some stimulated absorption.

Because in CPT transform of this setting, photon directions would be reversed - laser would excite this target: increase probability of its atoms being excited.
Hence returning from CPT, it translates into increased probability of these atoms being deexcited.

I imagine there would be both - standard isotropic deexcitation, plus slightly increased probability of deexcitation in the direction of laser.

Thanks, I couldn't access this article ("downloaded 2 times"), but there is accessible another from J-PET team (next building to mine): "The tests of CP and CPT symmetry using the J-PET detector" https://www.epj-conferences.org/articles/epjconf/pdf/2019/04/epjconf_meson2019_05027.pdf

They study decay of positronium - this is microscopic CPT symmetry, while the suggested laser ring experiment is supposed to test macroscopic CPT symmetry ... from microscopic perspective asking if there is CPT analogue of "stimulated emission" as "stimulated absorption"?

Better than ring laser would be free electron laser (FEL), but they are much more difficult to access.

The problem I see is that ring laser, in contrast to FEL, has some percentage of photons traveling in the opposite direction - exciting our target, making its hypothetical stimulate deexcitation more difficult to detect.

What other problems can you point in such ring laser test of CPT symmetry?

Sure such continously excited lamp would deexcite - normally in isotropic way.

However, applying CPT symmetry to the above setting, CPT of laser would cause excitation of target,  what without CPT translates to additional directional radiation - increase of deexcitation rate in direction toward laser, I would like to test.

Applying CPT symmetry to this ring laser setting, would reverse photon directions - CPT(laser) would cause excitation of target ... hence returning from CPT symmetry, it means laser would cause deexcitation of target.

The central question is if after CPT symmetry physics works as ours (assumption used in the above statement) - including macroscopic physics, this experiment is supposed to test.

Maybe it doesn't, what would be also interesting and publishable - as probably first macroscopic CPT test (?), inspiring further experiments.

The problem I see is that, in opposite to free electron laser, such ring laser is not perfect - rather also has some small percentage of photons traveling in the opposite direction, exciting the target - making detection of hypothetical caused deexcitation more difficult.

The frequencies of excited target and laser need to overlap, the more the better, e.g. some gas discharge lamp with narrow spectrum, or maybe another laser.

I don't understand the need for SPDC? For now these are energy balance calorimetric-type measurements requiring high luminosity ... if successful, much better methods will be soon developed.

I have tried to organize such test of CPT symmetry in synchrotron, but it turns out technically challenging.
However, searching for a different laser having clear time asymmetry, a colleague has suggested that there are ring lasers - using optical isolator as kind of photon diode, enforcing photons traveling in one direction.

Applying CPT symmetry to the below setting, photons would travel in the opposite direction - causing excitation of the target (lamp).
So going back from CPT to to the original setting, shouldn't they cause deexictation of the target?

I am looking for access to ring laser to organize such test of CPT symmetry - please contact me in this case.

Better diagram for hypothetical https://en.wikipedia.org/wiki/Non-orientable_wormhole - if they are allowed by physics, there should be also allowed T(laser) causing deexictation of target.
If the above test of existence of such effect e.g. in synchrotron will turn out negative (working on it), it could be used e.g. as counterargument against possibility of non-orientable wormholes, or as argument for causality indeed working only in past->future direction (against CPT symmetry).
If the test would turn out positive, already possibility of stimulating deexcitation of target in chosen frequencies should probably quickly find hundreds of applications e.g. in technological processes, chemistry.

Electron is much more - quantized electric charge, somehow of finite energy (infinite for perfect point charge) ... plus magnetic dipole moment and angular momentum ... plus zitterbewegung/de Broglie clock - confirmed experimentally: https://link.springer.com/article/10.1007/s10701-008-9225-1

We can simulate some aspects of electron, but it seems we are still far from its complete understanding.

I also think it should remain valid in macroscopis physics - just imagine building larger and larger Feynman diagrams.

However, CPT naively reverses causality direction, like in this hypothetical rocket which traveled through Klein-bottle-like wormhole - what seems highly controversial.

Taking a setting with clear causality direction e.g. this laser causes excitation of its target later, if constructing CPT analogue of this situation, should CPT(laser) cause deexcitation of target earlier?

While building CPT analogue of laser seems technically extremely challenging, at least for free electron laser(FEL) it seems realizable: just replace electrons with positrons traveling in the opposite direction.

To test if it can cause deexcitation of target, we could use e.g. a gas-discharge lamp continuously exciting its atoms as the target - the big question is if such CPT(FEL) could increase deexcitation rate in this direction? (what could be measured monitoring lamp's energy balance)

I don't know and believe only experiment could really answer this question (?) - I would love to conduct (if only getting allowance to place such lamp e.g. in synchrotron?)

CPT symmetry (charge, parity, time) is at heart of modern physics:

Quote

The CPT theorem says that CPT symmetry holds for all physical phenomena

However, it seems treated seriously only in scale of Feynman diagrams with a few particles - is it still valid for macroscopic physics? Feynman diagrams of Avogadro's scale numbers of particles?

In other words, if preparing CPT(initial conditions), should they lead to CPT(their evolution) ... including time reversed causality direction?

While it seems technically challenging to prepare CPT(initial conditions), in theory general relativity allows to prepare T(initial conditions) - by hypothetical Klein-bottle-like wormholes ( https://en.wikipedia.org/wiki/Non-orientable_wormhole ) e.g. rotating 180 deg. light cones - while standard laser causes excitation of its target, would laser in a rocket traveled through such wormhole cause deexcitation of target?

Fully synthetic cells are already created and working (e.g. https://en.wikipedia.org/wiki/Artificial_cell ,  https://www.nist.gov/news-events/news/2021/03/scientists-create-simple-synthetic-cell-grows-and-divides-normally ) - for simple microbes it is just a matter of putting what's needed into phospholipid bag ... and there are financial motivations: to cheaply synthesize mirror chemicals e.g. for drugs.

It is quite likely there will be first mirror microbes in a decade - it is now time to prepare for that: understand the dangers (e.g. taking over ecological niches while being toxic), try to prevent them ...

Thanks, added to https://en.wikipedia.org/wiki/Mirror_life

... mirror microbe by 2040?

Radiation of linear antenna is probably detected everyday, the question is minimal size of rotating dipole to still radiate EM waves?

So what is the minimal number of atoms building a dipole, such that the radiation power formula from the first post still works?

4 minutes ago, swansont said:

So…not femtoseconds.

Indeed, while both calculations suggest alignment already for classical magnets, they seem to lead to essentially different times for such process - bringing interesting question of which is more appropriate, has better agreement with experiment.

So please take a look in the attached article - calculations for classical magnet in external magnetic field - satisfying below equation (3), do you disagree with it?

Sure such magnet is built of atoms, but I don't think atomic physics is a proper description for antenna (?)

You are focusing on internal atomic physics of these atoms, but please also take a look at the classical picture e.g. in calculation of this article.

Imagine you have a nanonmagnet built of a thousand of atoms - I think you agree we can treat it as a classical magnet, so this classical calculation should be valid (?)

EM radiated energy during such classical alignment might not necessarily be localized like photons (?) - rather as EM radiation of cylindrically symmetric antenna, suggesting such EM wave might be e.g. cylindrically symmetric ... I don't know if atomic physics describes well antennas?

Now reduce the number of atoms one by one to a single atom ...

Ok, maybe I should use e.g. "excessive" word instead - generally a system having excessive energy (larger than minimal), has tendency to release this energy.

E.g. excited atom has tendency to release excessive energy as EM radiation (photon carrying the difference of energy, momentum, angular momentum) - deexciting to energy minimum of the ground state.

I see unaligned "classical" magnetic dipole in external magnetic field analogously - this field causes precession, which means excessive kinetic energy - which can be released through EM radiation, leading to aligned magnetic dipole without this excessive energy.

If you want more formal classical calculation, there is a deep analysis in the linked article.

Sure this is different description than quantum, the big question is where is the boundary?

Why cannot they be just different perspectives on the same systems? Like phonons which are both normal modes, and effects of creation operator in perturbative QFT ...

4 minutes ago, exchemist said:

The passage you quoted is not a classical treatment, but a QM treatment. That's what the wave function integral is about.

There is no way for a classical treatment to give you a series of beams, corresponding to discrete orientations. You would get a continuum, since all possible orientations are allowed - or just one spot if the particles had time to orient themselves with the field before exiting it.  

The article ( https://www.preprints.org/manuscript/202210.0478/v1 ) uses classical electromagnetism - just a magnet in external magnetic field: should not only precess, but also finally align in parallel or anti-parallel way, what can be imagined e.g. as EM radiation of abundant (kinetic) energy, or direct calculation in this article.

Please point mistake, problem in this derivation ... or if you cannot, the size boundary where it no longer works?

As classical it should work for large magnets - made from how many of atoms? A million? A thousand? ... a single atom? electron?

Experimentally it agrees also with the last two ... so where do you see the classical-quantum boundary here?