Concerns: Better control is needed over moment structure (gates to moment customization) at construction and transformation time. NISQ users perform simplifying transformations by hand rather than using Cirq circuit transformers. Currently, cirq.merge_single_qubit_moments_to_phxz has poor performance. Cirq also has poor scaling of transformations for larger circuits.

• Identify concrete use cases where the concerns above arise.
• Explore if there is a common pattern for new customizable transformers that would satisfy missing needs.
• Establish what transformers need to be improved for large circuits and optimize them to meet the required throughput.
• Ensure these transformers are covered by ASV benchmarks to guard against performance regressions.