A Russian "transhumanist and life extensionist" named Alexey Turchin has published his plan for bringing people back to life.
Called technological resurrection, a super-powered artificial intelligence uses a Dyson Sphere megastructure "to harness computing energy from the sun." That will provide the Sphere the power it needs to collect all the historical and personal information possible about a person. It then rebuilds a digital copy of that individual.
From that point, a person will live their entire life again, but this time in a simulated reality. Just like the first biological life, a person's digital life will also end in death, at which point Turchin theorizes they will be sent to a simulated afterlife with all of humanity (the simulated beings) in the same place.
Turchin and fellow researchers have published their "Immortality Roadmap" for how it's all possible:
Turchin has been fascinated by the idea of immortality ever since he was 11 years old and a young girl in his class at school died. He believes the Dyson Sphere is the key to making it happen.
Humans do not have the capability to construct a Dyson Sphere, but researchers say that nanorobots could one day do so.