Single particles of light (photons) to simulate quantum particles travelling through time were just used by scientists from the University of Queensland, Australia. They showed that one photon can pass through a wormhole and then interact with its older self. Their findings were published in Nature Communications.
Closed timelike curves are a concept necessary to understand this experiment(CTC). CTCs are used to simulate powerful gravitational fields, like the ones produced by a spinning black hole, that could theoretically (based on Einstein’s theory of general relativity), warp the fabric of existence so that spacetime bends back on itself. This creates a CTC, almost like a pathway to travel back through time.
“It’s intriguing that you’ve got general relativity predicting these paradoxes, but then you consider them in quantum mechanical terms and the paradoxes go away.” – University of Queensland physicist Tim Ralph (source)
Tim Ralph (quoted above) and his PhD student Martin Ringbauer simulated a Deutsch’s model of CTCs, according to Scientific American, “testing and confirming many aspects of the two-decades-old theory.” Although it’s just a mathematical simulation, the researchers (and their team/colleagues) emphasize that their model is mathematically equivalent to a single photon traveling through a CTC. Nothing has actually been sent back through time though; to do that, scientists would have to find a real CTC, which has yet to happen as far as we know. Of course, there always remains the possibility that black budgetscience has.
Think in terms of the ‘grandfather paradox,’ a hypothetical scenario where someone uses a CTC to travel back through time to cause harm to their grandfather, thus preventing their later birth. Now imagine a particle going back in time to flip a switch on the particle-generating machine that created it – this is a possibility that these physicists say they have shown through their simulation.
You can read the specifics of the experiment here.