# Test of CPT symmetry with ring laser (or free electron laser)?

#### Jarek Duda

Registered Senior Member
CPT symmetry Wikipedia article says "The CPT theorem says that CPT symmetry holds for all physical phenomena". However, while e.g. laser cooling could be seen as CPT analogue of laser heating, there are phenomena for which it seems there is no CPT analogue, like stimulated emission (?) - are there any arguments, experimental tests to confirm or deny it?

I would like to organize such a test using ring laser (or free electron laser) - it uses optical isolator
as kind of photon diode, enforcing photons traveling in one direction.

Applying CPT symmetry to the shown 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 laser cause deexictation of the target? (lamp continuously excited in corresponding spectrum, directional deexcitation in addition to standard isotropic radiation).

I am looking for access to ring laser to organize such test of CPT symmetry - it would be probably the first such test, so even if negative should be well publishable and inspire further. If you know somebody having access to such laser and potentially open for such collaboration, please contact me.

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.

- ?

Optical pulling allows to pull in optical tweezers, negative radiation pressure to pull solitons - some hypothetical application: 2WQC (two-way quantum computers) maybe solving 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 (details in Section V of https://arxiv.org/pdf/0910.2724 )