Abstract
Coherent many-body quantum dynamics lies at the heart of quantum simulation and quantum computation. Both require coherent evolution in the exponentially large Hilbert space of an interacting many-body system. To date, trapped ions have defined the state of the art in terms of achievable coherence times in interacting spin chains. Here, we establish an alternative platform by reporting on the observation of coherent, fully interaction-driven quantum revivals of the magnetization in Rydberg-dressed Ising spin chains of atoms trapped in an optical lattice. We identify partial many-body revivals at up to about ten times the characteristic time scale set by the interactions. At the same time, single-site-resolved correlation measurements link the magnetization dynamics with interspin correlations appearing at different distances during the evolution. These results mark an enabling step towards the implementation of Rydberg-atom-based quantum annealers, quantum simulations of higher-dimensional complex magnetic Hamiltonians, and itinerant long-range interacting quantum matter.
- Received 28 August 2017
DOI:https://doi.org/10.1103/PhysRevX.7.041063
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
Quantum computers promise solutions to tasks that are intractable by classical machines, such as problems relevant to cryptography, material science, quantum chemistry, and classical optimization. Quantum magnets based on ultracold atoms trapped in optical lattices provide one way to create a special type of quantum computer known as a quantum annealer. To achieve the promised quantum speedup, a quantum annealer requires coherent and fine-tuned interactions among the spins of its atoms. An annealer can be implemented in cold atomic gases by off-resonant optical coupling to long-range interacting “Rydberg states,” states in which one electron of the atom is highly excited. Induced and controlled by laser light, such “Rydberg-dressed” interactions come with a large degree of tunability, distinguishing them from other types of engineered spin interactions in cold atomic gases. In our work, we experimentally realize quantum magnets with such optically induced long-range spin interactions.
Contrary to earlier experiments, our system features unmatched long coherence times. We probe this by tracing a process unique to the quantum world: collapse and revival of the transverse magnetization. Starting in a fully polarized state of maximal magnetization, the interaction first dephases the spins. This results in a decaying magnetization, which later revives when the spins partially resynchronize at long observation times. Local detection with a quantum gas microscope that is sensitive to single atoms allows us to shed light on the remaining decoherence processes as well as the microscopic mechanisms of the collapse and revival dynamics.
Our results mark an important step that pushes the coherence of synthetic quantum magnets toward the implementation of a Rydberg-dressed quantum annealer.