What are Qiskit primitives?

• Statevectorsampler: can sample the output quantum state from the quantum circuit in the computational basis. For example, if we have a circuit represented by a unitary $U$, Statevectorsampler can sampler $U|0\rangle$.

• StatevectorEstimator: can estimate expectation values of observables with respect to the output quantum state of the quantum circuit. For instance, if we have a circuit represented by a unitary $U$ and an observale $O$ we'd like to measure, StatevectorEstimator calculates $\langle 0|U^{\dagger}OU|0\rangle$.

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Reference

1. PENNYLANE - Qiskit primitives: https://pennylane.ai/qml/glossary/what-are-qiskit-primitives
2. Qiskit 101