228th RQC Seminar

• 講演者

  Dr. Nikita Astrakhantsev
  ( Google Quantum AI )

• 日程

  2025年9月25日(木), 11:00 - 12:00 (11:00 a.m. - 12:00 p.m.)

• 開催場所

  ハイブリッド（ZOOM・ Wako Chemistry and Materials Physics Building 5F S507 Meeting Room / 物質科学研究棟5階 S507 会議室 (S51))

• 講演タイトル

  Constructive Interference at the Edge of Quantum Ergodic Dynamics

• お問合せ

  yasunobu.nakamura[at]riken.jp

講演概要
Quantum observables in the form of few-point correlators are the key to characterizing the dynamics of quantum many-body systems. In dynamics with fast entanglement generation, quantum observables generally become insensitive to the details of the underlying dynamics at long times due to the effects of scrambling. In experimental systems, repeated time-reversal protocols have been successfully implemented to restore sensitivities of quantum observables. Using a 103-qubit superconducting quantum processor, we characterize ergodic dynamics using the second-order outof-time-order correlators, OTOC^2. In contrast to dynamics without time reversal, OTOC^2 are observed to remain sensitive to the underlying dynamics at long time scales. Furthermore, by inserting Pauli operators during quantum evolution and randomizing the phases of Pauli strings in the Heisenberg picture, we observe substantial changes in OTOC^2 values. This indicates that OTOC^2 is dominated by constructive interference between Pauli strings that form large loops in configuration space. The observed interference mechanism endows OTOC^2 with a high degree of classical simulation complexity, which culminates in a set of large-scale OTOC^2 measurements exceeding the simulation capacity of known classical algorithms. Further supported by an example of Hamiltonian learning through OTOC^2, our results indicate a viable path to practical quantum advantage.

Reference: https://arxiv.org/pdf/2506.10191