Example Concept: Decoherence refers to the loss of quantum coherence in qubits, where quantum information is lost to the environment, causing errors in quantum computations. In iterative variational algorithms, such as the Variational Quantum Eigensolver (VQE), decoherence can lead to inaccurate energy estimations and hinder the optimization process. Techniques like dynamical decoupling, error correction codes, and noise-aware circuit design are employed to mitigate these effects and improve algorithmic outcomes.