Quantum gas microscopy of Kardar-Parisi-Zhang superdiffusion

Area of Science:

• Condensed Matter Physics
• Quantum Simulation
• Statistical Mechanics

Background:

• The Kardar-Parisi-Zhang (KPZ) universality class typically describes classical stochastic models.
• A recent conjecture proposed KPZ universality also governs spin transport in the one-dimensional quantum Heisenberg model.
• Experimental verification of KPZ scaling in quantum spin systems is crucial for understanding universal dynamics.

Purpose of the Study:

• To experimentally test the conjecture that KPZ universality describes spin transport in the quantum Heisenberg model.
• To investigate the conditions required for KPZ scaling in quantum spin chains.
• To probe the nonlinear dynamics characteristic of KPZ universality in a quantum system.

Main Methods:

• Utilized a cold-atom quantum simulator to study spin chains up to 50 spins.
• Experimentally probed domain-wall relaxation dynamics in the spin chains.
• Employed single-spin-sensitive detection using a quantum gas microscope to measure spin-transport statistics.

Main Results:

• Confirmed that domain-wall relaxation in the quantum Heisenberg model is governed by the KPZ dynamical exponent z = 3/2.
• Demonstrated that KPZ scaling necessitates both integrability and nonabelian SU(2) symmetry.
• Measured a spin-transport observable, providing a clear signature of the nonlinearity characteristic of KPZ universality.

Conclusions:

• The study provides the first experimental evidence for Kardar-Parisi-Zhang universality in the one-dimensional quantum Heisenberg model.
• Integrability and nonabelian SU(2) symmetry are identified as critical requirements for KPZ scaling in this quantum system.
• The findings open new avenues for exploring universal nonlinear dynamics in quantum many-body systems.