Amazing stuff! Possibly a breakthrough!
"... Now Google “is launching a new analog-digital hybrid approach for quantum simulation to try and get the best of both worlds,” ...
The new system possesses 69 superconducting qubits. It begins its simulations by applying gates to qubits to prepare the initial states of the model, and then lets the model quickly evolve in an analog manner. Finally, it returns to digital performance so that researchers can measure the results in an extensive way. “We get a combination of flexibility and speed,” ...
Previous research had explored analog-digital hybrid quantum simulation, but it often suffered from large errors during the analog evolution stage. The new system employed a high-fidelity calibration scheme that significantly reduced this problem, achieving a 0.1 percent error rate per qubit. “This was one of the breakthroughs that made this work possible,” ..."
From the abstract:
"Understanding how interacting particles approach thermal equilibrium is a major challenge of quantum simulators. Unlocking the full potential of such systems towards this goal requires flexible initial state preparation, precise time evolution and extensive probes for final state characterization.
Here we present a quantum simulator comprising 69 superconducting qubits that supports both universal quantum gates and high-fidelity analogue evolution, with performance beyond the reach of classical simulation in cross-entropy benchmarking experiments.
This hybrid platform features more versatile measurement capabilities compared with analogue-only simulators, which we leverage here to reveal a coarsening-induced breakdown of Kibble–Zurek scaling predictions in the XY model, as well as signatures of the classical Kosterlitz–Thouless phase transition.
Moreover, the digital gates enable precise energy control, allowing us to study the effects of the eigenstate thermalization hypothesis in targeted parts of the eigenspectrum.
We also demonstrate digital preparation of pairwise-entangled dimer states, and image the transport of energy and vorticity during subsequent thermalization in analogue evolution.
hese results establish the efficacy of superconducting analogue–digital quantum processors for preparing states across many-body spectra and unveiling their thermalization dynamics."
Fig. 1: Analogue–digital simulation with high-precision calibration.
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