Brian M
Sort of makes sense - But does make a presumption that time is a travelable dimension (as we can and do in 3 dimensions). Unfortunately we really don't understand the nature of what time is or if it actually even exists other than in our own perceived concept of a historical timeline and relativity.

This seems to assume almost exactly what it claims to prove. In the experiment, the single Qbit gets changed, but nothing else does, and all the other entanglements essentially resurrect the Qbit (if I understand correctly). But in a more realistic model it seems to me that the changes made in that Qbit (or anything else) would propagate outward and change the rest of the system?
"reality is more or less “self-healing,” so changes made to the past won’t drastically alter the future you came from – at least, in the quantum realm."

IMHO, concept of spacetime in macro scale/world is an emergent property!
Just like concept of water/fluid (which only exists in macro scale/world & NOT in micro (atomic/molecular) scale/world)!

Would we expect removing a water molecule, could really make any noticeable difference in macro scale structure/movements of any piece of water/fluid?
(I think the answer is no & it can be easily proven w/ any computer fluid simulations!)

But, still, realize, we already know/proven that Butterfly Effect is quite real & powerful for any fluids/weather!

So, IMHO, this result does NOT really prove that time travel into past can be harmless!

(By the way, IMHO, spacetime is a superfluid created by gas-like dynamics of virtual particles of quantum vacuum!)
James Macaluso
To speculate, could it also be possible that a variable manipulated further in the past would simply have additional variables to affect along its now seperate time frame before we could register changes from our point of view of temporal incusion. To use the grandfather paradox to simplify; murdering grandfather 70 years ago and returning to the present wondering why I still exist... I now would require an additional 70 years before any of the results of my past meddling became apparent to myself since those altered elements now exist in a temporal vacuum and must ripple forward to affect all other variables. In short I propose that the results in the present would not be immediately apparent as we have now created an alternate time stream of cause and effect assuming a fluid singular universe model.
There is a joke that asks "Do you know why God created time?" The correct response is "So everything doesn't happen at once!" Seems to me that makes about as much sense as anything else. I only hope that none of my tax money paid for this experiemnt.
So much for free will it seems...

@Brian - backwards time is a travelable dimension (experiments have succeed in changing changing the past).
Douglas Bennett Rogers
Maybe there are five extended dimensions, length, width, height, time, and probability. An entity perceives a volume, (dx, dy, dz, dt). The entity acts on the volume, producing an array. At time, t2, the entity picks an element of the array, which becomes the basis of the entity's universe. All of the other elements still exist and fulfill the requirements of past history alteration.
A confusion I have about time travel to the past that is exemplified by the 'kill my grandfather' paradox is as follows: Suppose I travel back in time, taking a gun with me, and shoot and kill my grandfather a year before my father is conceived. That gun is made of a variety of atoms, mostly iron, that existed at that previous time. The iron atoms were probably in some magnetite iron ore on a mountainside at that time. So now all the molecules in my gun are at two places at once. This also applies to all the atoms in my body and in my time machine and anything else a took back in time with me. How does that work? Forget about my act of grandpapacide, won't this happen for any travel back in time, i. e., the instantaneous duplication of all the atoms going back in time? Has Calvin (of Calvin and Hobbes fame) figured this out?
Ralf Biernacki
@James: but by the time the disturbance has propagated the 70 years forward and reached the present, the present has moved---you are now another 70 years forward. In other words, if things work as you assume, the past will be rolling over, but the changes will never catch up with you---the "front" will always be 70 years in the past. That's very interesting: in a world that works like that, you can travel to the past and change it, but to experience the results of the change you must stay in the past. If you return, nothing will have changed for you. But if you travel into the past again, you will land in the altered past. What if someone else changes it in the meantime? It could end up so that if you travel to the past, you will find that it has no resemblance to the past that you expect, as recorded in history books---it is a completely different timeline resulting from many interventions. And the farther back you go, the more numerous the differences.
James Macaluso

What you propose is also very fascinating. I would never presume to be an expert on such things, I just enjoy thinking of such things. One place where I believe you missunderstood my supposition is that I do believe the future would be altered by our traveling to the past; however, I think not in the manner depicted in the movies.

For another example, I travel back in time 5 minutes and move my pen from my desk to the refrigerator. Then I return to the present to see my pen still on my desk. In another 5 minutes it will move to the refrigerator once the altered time stream catches up to me.

Now if multiple people begin time traveling and altering the past, then yes I believe any past we jump into would become quite chatoic and possibly unfamiliar, if I understand commenter Rogers postulation, as there would not only be our original 4th to contend with but the 4¹ that we altered as well as all others. I believe that each change to the past creates a mobile ripple of changes that eventually over writes the present.

On a completely different note, would we not be bringing diseases we are immune to into the past to a civilization unprepared for them and possibly wiping out massive swaths of life forms? Would our travel a great distance into the future be equally as dangerous to ourselves personally?