Accidentally hit my head on the toilet and came up with a flux capacitor, jokes aside, but here is a time machine concept?
You see a double split experiment, where a particle is determined as an wave or an particle depending on the observation of it.
The idea is, Send this light down a tunnel (Bounce it back or forward, or a long of mirrors or w/e that slows light down as much as possible might have to be pretty big),
then into the double slit, of which the screen has an interference pattern.
Now here's the beauty, determine its a particle or wave at the double slit, (wait into experiment done), then look under the box. It should read a 0 or 1 according to what the light ends up being.
So in theory, this should send the information back a few seconds?
Or perhaps this:An beam splitter, of which into the box and into the tunnel. Determine at the end of the experiment, and change the outcome inside the box.

Delayed Quantum Eraser Experiment Tweak Invention:
Mentions of regards to delayed quantum eraser:The experiment shown in 1999, the delayed quantum eraser paper, that observing with A or B caused it to be in an erased state of state 1, and not observing with A or B caused it to be in state 2.
In the 1 light-year picture figure below example:A person is looking at the screen in 2020 On Earth, it takes to 2021 for it to reach A/B Destination. The person on Earth would already see it's either state 1 or 2 in 2020 while looking at the screen, as it travels to A/B detectors Accordingly in 2021. (Takes 1 year to reach its destination speed of light)
Another person presses a red button in 2021 on say another planet, turning A/B detectors off, resulting in state 2. Sending, the information 1 year into the past of 2020. The person looking at the screen on Earth would have already seen it in state 1 or state 2.

OMG!! I want to be your first passenger...