aiqbench takeQuantum Computing

This is theoretical quantum many-body physics: it shows that exact scar towers can be built in spin chains via unitary transformations within embedded subspaces, without full Hamiltonian matching. For quantum readers, the relevance is conceptual. It maps how non-thermal behaviour survives inside fragmented Hilbert spaces, which bears on quantum simulation and on how far constrained dynamics can be engineered. It is foundational work with no demonstrated hardware or application yet.

Source coveringQuantum Zeitgeist

Tokyo Team Links Fragmentation to Quantum Scars in Spin Chains

Quantum ZeitgeistOctober 25, 20265 min read

Previously, preserving quantum many-body scars demanded maintaining strict Hamiltonian equivalences during system deformation. Now, this work reveals constructing an *exact* scar tower is possible via unitary transformations, even when complete Hamiltonian matching fails. This establishes how fragmentation hierarchies reduce to single scarred states, offering potential control over non-thermal behaviour in complex systems.

Successive local deformations reduce extensive irreducible-string fragmentation through an implicitly embedded spin-1/2 invariant space. This process ultimately leads to a single scar tower connecting the XXC, perturbed XXC, and spin-1 XY scar models. Local dynamics couples states from distinct frozen irreducible-string sectors via this intermediate embedded space and selects a new decomposition into representations. Smaller invariant spaces are then able to be retained as a result. A key constraint on isolating nonsymmetric towers is also established. Furthermore, a constructive correspondence transferring a reduction between locally realizable representations of the embedded dynamics is demonstrated. ## Unitary Transformation Preserves Reduction…

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