CI-2: Implement Observable/Estimator backends

[yuyamashiro]

Priority: High

Description

The ObservableEstimator protocol currently only has protocol definitions. Backend-specific implementations need to be completed for expectation value estimation.

Dependencies

None

File

qamomile/circuit/observable/estimator.py

Tasks

• Concrete implementation of ObservableEstimator protocol
• Complete QiskitExpectationEstimator
• Complete QuriPartsEstimator
• Implement CudaqEstimator
• Sampling-based expectation value estimation

Tests

• Expectation value calculation for Pauli observables

Related

See Development Roadmap for full context.