Observation and Modulation of the Quantum Mpemba Effect on a Superconducting Quantum Processor

Area of Science:

• Quantum physics
• Condensed matter physics
• Quantum information science

Background:

• The quantum Mpemba effect (QME) is a counterintuitive phenomenon in nonequilibrium quantum systems where faster symmetry restoration is observed in systems with greater initial symmetry breaking.
• While theoretical studies on QME dynamics are extensive, experimental investigations, particularly on flexible modulation, are limited.
• Understanding and controlling QME is crucial for advancing quantum information science and exploring quantum many-body dynamics.

Purpose of the Study:

• To experimentally observe and flexibly modulate the quantum Mpemba effect (QME) in a controllable quantum system.
• To investigate the influence of coupling regimes, on-site potentials, and initial states on QME dynamics.
• To utilize entanglement asymmetry (EA) as a sensitive probe for quantifying symmetry restoration in QME.

Main Methods:

• Utilized a superconducting processor with an all-to-all connected, tunable-coupling architecture for precise control over interactions.
• Independently manipulated coupling strengths (short-range vs. intermediate-range), on-site potentials, and initial states (tilted Néel and ferromagnetic states).
• Employed quantum state tomography to reconstruct the density matrix and calculated entanglement asymmetry (EA) to quantify symmetry restoration.

Main Results:

• Observed QME in strong short-range coupling regimes via EA crossovers during quenches from tilted Néel states.
• Demonstrated suppression of QME in intermediate-coupling regimes, evidenced by synchronized EA and entanglement entropy dynamics.
• Showcased reemergence of QME with the addition of on-site linear potentials or quenches from tilted ferromagnetic states, with the latter showing robustness against disorder.

Conclusions:

• Successfully demonstrated flexible modulation of QME on a superconducting quantum processor with multiple controllable parameters.
• Elucidated the distinct roles of coupling regimes, potentials, and initial states in influencing QME.
• Opened new avenues for studying quantum many-body nonequilibrium dynamics and exploring potential applications in quantum information processing.