---

name: simulation-study-and-noise description: "Run local Cirq simulator, sampler, sweep, histogram, state, density-matrix, Clifford, and noisy-channel workflows." disable-model-invocation: true metadata: disco-role: operating license: Apache 2.0

Simulation, study, and noise

Use this sub-skill when a task asks you to execute Cirq programs locally, choose a simulator or sampler, run parameter sweeps, inspect measurement results, visualize histograms, simulate state vectors or density matrices, or add local noise/channels.

Route here for

• cirq.Simulator, cirq.DensityMatrixSimulator, cirq.CliffordSimulator, and cirq.sample.
• run, run_sweep, simulate, and simulate_sweep decisions.
• Result.histogram, Result.multi_measurement_histogram, and plot_state_histogram usage.
• Linspace and Points sweeps, parameter resolver troubleshooting, and repeated sampling.
• Local noisy simulation with depolarize, amplitude_damp, phase_damp, bit_flip, ConstantQubitNoiseModel, and Circuit.with_noise.

Route elsewhere

• Circuit object construction, custom gates, qids, measurement-key basics, JSON/QASM object handling: core-circuits-and-ops.
• Circuit transformation, decomposition, target-gateset optimization, routing, and compilation before simulation: transformers-and-compilation.
• Cloud samplers, provider credentials, hardware jobs, and provider serializers: hardware-providers-and-serialization.
• Algorithm design, Pauli observables, expectation-value workflows, and textbook circuit recipes: algorithms-and-observables.

Operating checklist

1. Decide whether the user needs samples, sweeps, or final state data.
2. Choose the smallest adequate backend: pure-state Simulator, mixed-state DensityMatrixSimulator, stabilizer-only CliffordSimulator, or quick cirq.sample.
3. Ensure all symbolic parameters are resolved through a resolver or sweep before numeric simulation.
4. Ensure sampling circuits have explicit measurement keys, then read counts through Result histogram methods.
5. For non-unitary channels/noise models, use density-matrix simulation when the post-noise state itself matters.
6. Set seeds for deterministic demonstrations and tests; treat noisy counts as statistical unless repetitions and seed are controlled.

Bundled references and script

• API signatures and simulator-selection guide: references/api-reference.md
• End-to-end local workflows: references/workflows.md
• Simulator and histogram troubleshooting: references/troubleshooting.md
• Safe local noisy-sampling smoke demo: scripts/run_noisy_smoke.py