There are lots of experimentalists here, so I thought to ask if somebody has (or know somebody having access to) ring laser (or free electron laser, synchrotron)? - please contact me if so.

They might allow for currently unknown effect (increase deexcitation rate of target) - which if true would allow for lots of new applications including fusion, e.g. stimulation of improbable nuclear transitions.

Ring laser with optical isolator (acting as diode for photons) allows for nearly unidirectional photon trajectories.

CPT theorem says that "CPT symmetry holds for all physical phenomena" - applying this symmetry to ring laser would reverse photon trajectory, making it should ** cause excitation of target** in below diagram. In the original perspective (no CPT) it translates to

**causing deexcitation of target**__.__

Assuming this target is gas-discharge lamp, its excited atoms usually deexcite in isotropic way - the question is if such laser can additionally __increase probability of deexcitation in this direction__ (and corresponding frequency)? In this case it would be seen by detectors around.

It needs experimental test - negative result would suggest macroscopic CPT violation (and its further investigation), positive would allow for lots of new applications.

ps. to spice potential "new applications", such hypothetical caused deexcitation would be earlier - what might allow e.g. for time-loop computers (more details in Section IV.A of https://arxiv.org/pdf/0910.2724 ) :