A randomized quench protocol enables the first fully analog measurement of infinite-temperature OTOCs on Rydberg atom arrays, revealing information propagation lightcones.
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Constructive inter- ference at the edge of quantum ergodic dynamics
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abstract
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 out-of-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.
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Krylov winding emerges as a generic feature of quantum chaotic systems from the universal operator growth bound, producing size winding when a low-rank Krylov-to-size mapping exists and the chaos bound saturates.
Unitary designs emerge from the temporal ensemble of two chaotic Hamiltonian evolutions separated by a random Pauli operation, based on the universal Pauli spectrum.
In a chaotic quantum system, higher-order correlations reach thermal equilibrium faster than state design moments, both relaxing exponentially.
Adiabatic evolution prepares local thermal states from initial Gibbs states while conserving entropy density in the thermodynamic limit, with mirror-circuit benchmarking of hardware noise entropy demonstrated experimentally on a 5x4 Ising model.
QESEM is a characterization-based error mitigation technique that achieves unbiased estimates with substantially reduced runtime cost compared to probabilistic error cancellation while outperforming zero-noise extrapolation on utility-scale circuits.
In a monitored dissipative spin model realizable on Rydberg simulators, free-energy functionals applied to trajectory ensembles identify dynamical features akin to hydrophobic effects in classical phase transitions.
NISQ quantum-advantage demos keep falling to classical simulation because hardware-fidelity circuit regions coincide with classically compressible structure; exit requires fault tolerance.
Post-selection probability and fidelity of bidirectional teleportation are expressed via the Loschmidt echo, revealing initial-state dependence of fidelity and stability of probability in integrable models.
The paper identifies four key hurdles in the transition from NISQ to FASQ quantum computers and argues that targeting them will accelerate progress toward useful quantum advantage.
citing papers explorer
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Information Propagation in Rydberg Arrays via Analog OTOC Calculations
A randomized quench protocol enables the first fully analog measurement of infinite-temperature OTOCs on Rydberg atom arrays, revealing information propagation lightcones.
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Krylov Winding and Emergent Coherence in Operator Growth Dynamics
Krylov winding emerges as a generic feature of quantum chaotic systems from the universal operator growth bound, producing size winding when a low-rank Krylov-to-size mapping exists and the chaos bound saturates.
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Unitary Designs from Two Chaotic Hamiltonians and a Random Pauli Operation
Unitary designs emerge from the temporal ensemble of two chaotic Hamiltonian evolutions separated by a random Pauli operation, based on the universal Pauli spectrum.
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Timescales for Deep and Full Thermalization
In a chaotic quantum system, higher-order correlations reach thermal equilibrium faster than state design moments, both relaxing exponentially.
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Adiabatic preparation of thermal states and entropy-noise relation on noisy quantum computers
Adiabatic evolution prepares local thermal states from initial Gibbs states while conserving entropy density in the thermodynamic limit, with mirror-circuit benchmarking of hardware noise entropy demonstrated experimentally on a 5x4 Ising model.
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Reliable high-accuracy error mitigation for utility-scale quantum circuits
QESEM is a characterization-based error mitigation technique that achieves unbiased estimates with substantially reduced runtime cost compared to probabilistic error cancellation while outperforming zero-noise extrapolation on utility-scale circuits.
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Revealing emergent many-body phenomena by analyzing large-scale space-time records of monitored quantum systems
In a monitored dissipative spin model realizable on Rydberg simulators, free-energy functionals applied to trajectory ensembles identify dynamical features akin to hydrophobic effects in classical phase transitions.
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The NISQ Trap: Eight Years of Demonstrations the Hardware Was Built to Lose
NISQ quantum-advantage demos keep falling to classical simulation because hardware-fidelity circuit regions coincide with classically compressible structure; exit requires fault tolerance.
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Post-Selection Probability and Fidelity of Bidirectional Teleportation
Post-selection probability and fidelity of bidirectional teleportation are expressed via the Loschmidt echo, revealing initial-state dependence of fidelity and stability of probability in integrable models.
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Mind the gaps: The fraught road to quantum advantage
The paper identifies four key hurdles in the transition from NISQ to FASQ quantum computers and argues that targeting them will accelerate progress toward useful quantum advantage.