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Why are VQE runs often constrained by decoherence time?

Asked on Nov 01, 2025

Answer

Variational Quantum Eigensolver (VQE) runs are often constrained by decoherence time because the quantum circuits used in VQE must maintain coherence long enough to accurately perform the necessary gate operations and measurements. Decoherence leads to loss of quantum information, which can significantly affect the accuracy of the VQE results, especially when dealing with complex molecules or materials.

Example Concept: Decoherence time is the duration over which a quantum system, such as a qubit, maintains its quantum state without losing information to the environment. In VQE, maintaining coherence is crucial because the algorithm relies on iterative quantum measurements and adjustments to minimize the energy of a quantum system. If decoherence occurs too quickly, the qubits may not accurately represent the desired quantum state, leading to errors in the energy estimation.

Additional Comment:

VQE is a hybrid quantum-classical algorithm, which means it uses a quantum processor to evaluate the energy of a system and a classical optimizer to adjust the parameters of the quantum circuit.
Decoherence can be mitigated by using error correction codes, shorter circuit depths, or optimizing gate operations to fit within the coherence time.
Superconducting qubits and trapped ions are common hardware platforms for VQE, each with different coherence times and error rates.
Improving coherence times is a key area of research in quantum hardware development.

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Why are VQE runs often constrained by decoherence time?

Asked on Nov 01, 2025

Answer

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