Update README.md

Author: jiaqileng

README.md

@@ -5,9 +5,9 @@
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-**QHDOPT** (QHD-based OPTimizer) is a software package for nonconvex optimization.
+**QHDOPT** (QHD-based OPTimizer) is a software package for nonlinear optimization.
 
-QHDOPT implements a quantum optimization algorithm named [Quantum Hamiltonian Descent](https://jiaqileng.github.io/quantum-hamiltonian-descent/) (QHD) on available quantum computers (such as the [D-Wave systems](https://www.dwavesys.com/)). QHD is a quantum-upgraded version of gradient descent (GD). Unlike the classical GD, QHD demonstrates a significant advantage in solving nonconvex optimization problems.
+QHDOPT implements a quantum optimization algorithm named [Quantum Hamiltonian Descent](https://jiaqileng.github.io/quantum-hamiltonian-descent/) (QHD) on available quantum computers (such as the [D-Wave systems](https://www.dwavesys.com/)). QHD is a quantum-upgraded version of gradient descent (GD). Unlike the classical GD, QHD demonstrates a significant advantage in solving nonconvex and nonlinear optimization problems.
 
 <p align="center">
 <img src="img/workflow.png" alt="QHDOPT Workflow" width="600">