IBM quantum hardware has successfully simulated a 100-site spin chain, achieving 97.9-99.0% fidelity in preparing ground states of the chain, a scale previously limited by the entanglement needed for accurate results. Researchers used a tensor-network-based approximate quantum compiling protocol to construct shallow circuits, with a depth of only 18-39 CNOT gates, to explore symmetry-protected topological (SPT) order.
The work directly measured string order for lengths up to 20, persisting beyond the decay of conventional correlations, alongside other non-local diagnostics, offering a new way to characterise these complex quantum states. This establishes digital quantum devices as flexible platforms for studying complex quantum matter.
These circuits, ranging from 18 to 39 CNOT gates in depth, enabled the preparation of the 100-site ground states, a scale that pushes the boundaries of current digital quantum hardware. This reduction in circuit complexity is crucial for minimizing errors and maintaining the coherence of quantum information. The ability to prepare these states with high fidelity is a major step forward in the field of quantum simulation, allowing for more accurate and reliable studies of complex quantum phenomena.
Beyond simply preparing the quantum state, the researchers directly measured multiple non-local diagnostics of SPT order. This observation provides strong evidence for the presence of SPT order, a characteristic difficult to observe with traditional experimental techniques. The team observed entanglement spectrum degeneracies and detected symmetry-protected edge modes. The simultaneous observation of these independent diagnostics provides a scalable and programmable approach to preparing and characterising SPT phases on quantum processors, as detailed in their published work.
This establishes digital quantum devices as versatile platforms for investigating complex quantum matter, with access to microscopic observables that are difficult to obtain in conventional experimental systems. This also establishes digital quantum devices as flexible platforms for studying complex quantum matter and provides a practical foundation for exploring non-equilibrium dynamics in regimes that challenge classical computational methods.
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