01735nas a2200145 4500008004100000245007200041210006900113260001400182490000800196520127600204100003501480700002501515700002801540856002101568 2023 eng d00aQuantum simulations of time travel can power nonclassical metrology0 aQuantum simulations of time travel can power nonclassical metrol c11/3/20230 v1313 a
We construct a metrology experiment in which the metrologist can sometimes amend her input state by simulating a closed timelike curve, a worldline that travels backward in time. The existence of closed timelike curves is hypothetical. Nevertheless, they can be simulated probabilistically by quantum-teleportation circuits. We leverage such simulations to pinpoint a counterintuitive nonclassical advantage achievable with entanglement. Our experiment echoes a common information-processing task: A metrologist must prepare probes to input into an unknown quantum interaction. The goal is to infer as much information per probe as possible. If the input is optimal, the information gained per probe can exceed any value achievable classically. The problem is that, only after the interaction does the metrologist learn which input would have been optimal. The metrologist can attempt to change her input by effectively teleporting the optimal input back in time, via entanglement manipulation. The effective time travel sometimes fails but ensures that, summed over trials, the metrologist's winnings are positive. Our Gedankenexperiment demonstrates that entanglement can generate operational advantages forbidden in classical chronology-respecting theories.
1 aArvidsson-Shukur, David, R. M.1 aMcConnell, Aidan, G.1 aHalpern, Nicole, Yunger uarXiv:2207.07666