Dynamical quantum simulation protocols are usually designed to measure a specific quantity, such as a response or correlation function. Yet the process implicitly prepares a family of many-body states that hold far more information than the original observable. A new study proposes exploiting these states as laboratories for quantum information, reusing data that is normally discarded after the measurement.

As a case study, the authors analyse local-pulse protocols used to compute Green functions in finite XX and XXX spin chains. They interpret opposite source rotations as encoding a classical bit into the many-body system. This makes it possible to track how the resulting record propagates, how it is shared across local subsystems, and how readily it can be recovered with different measurements.

The results show a clear separation between representation and readout. In the XX chain, fermionic covariance data exactly reconstruct the signed response, while in the XXX chain simple spin measurements recover a larger fraction of the locally available information. This reversed ordering persists when moving from finite-pulse discrimination to local source-angle estimation.

Going beyond the source record, the same reduced states allow the results to be reinterpreted in terms of Bell state recovery and quantum communication rates, while also giving direct access to the evolving bipartite and genuine multipartite entanglement of the system. The conclusion is that dynamical simulations developed for response calculations can naturally pose a much broader set of quantum-information questions about the many-body states they already prepare.