qiskit/releasenotes/notes/0.19/hhl-negative-eigenvalues-ef...

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---
features:
- |
The :obj:`.HHL` algorithm can now find solutions when its matrix has negative eigenvalues.
To enable this, the algorithm now adds an extra qubit to represent the sign of the value,
and the helper algorithm :obj:`.ExactReciprocal` was updated to process this
new information. See `#6971
<https://github.com/Qiskit/qiskit-terra/pull/6971>`__ for more details.