Communications of the ACM
Computing With Time Travel
Researchers at the National University of Singapore have shown a quantum computer can solve insoluble problems, even if it is is traveling along "open time-like curves."
Credit: Amblin Entertainment
About 10 years ago, Google's Dave Bacon showed a time-traveling quantum computer could quickly solve a group of problems, known as NP-complete, which are known for being very difficult. However, Bacon's quantum computer had to travel around "closed time-like curves," which are paths through the fabric of spacetime that loop back on themselves. General relativity shows such paths exist through contortions in spacetime known as wormholes, but physicists argue something must stop such opportunities from arising because it would threaten causality.
However, National University of Singapore (NUS) researchers have shown a quantum computer can solve insoluble problems even if it is traveling along "open time-like curves," which do not create causality problems. The researchers found these curves do not allow direct interaction with anything in the object's own past, meaning the time-traveling particles, or the data they contain, never interact with themselves.
Nevertheless, strange quantum properties that permit "impossible" computations are left intact, according to the researchers.
Quantum particles sent on a timeloop could gain super computational power, even though the particles never interact with anything in the past because some information is stored in the entangling correlation, which is what is being harnessed, according to NUS researcher Jayne Thompson.
From National University of Singapore
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