IBM chip builds a 100-site spin chain to study quantum matter

Researchers have successfully created a 100-site spin chain on IBM quantum hardware, a scale large enough to minimize limitations common in these experiments. The work demonstrates 97.9-99.0% fidelity in preparing ground states of the spin-1/2 bond-alternating Heisenberg chain, allowing for reliable extraction of data about symmetry-protected topological (SPT) phases. This programmable approach utilizes a tensor-network-based approximate quantum compiling protocol to achieve circuits with a CNOT depth of 18-39, directly extracting non-local diagnostics of SPT order, including string order for lengths up to 20, and establishing digital quantum devices as flexible platforms for studying complex quantum matter. This achievement bypasses limitations of traditional material platforms used to study symmetry-protected topological (SPT) phases, which often restrict tuning of Hamiltonian parameters and access to the underlying quantum state. The team’s success hinges on the ability to move beyond the Landau paradigm of quantum matter, which traditionally relies on identifying local order parameters; SPT phases, however, exhibit distinct characteristics lacking such conventional markers. Diagnosing these phases typically depends on indirect probes like boundary states, but the IBM processor enabled direct extraction of non-local properties of the many-body wavefunction, offering a more complete picture of the system’s quantum state. 97.9-99.0%, ensuring the reliability of extracted…