Add Suzuki-Trotter to C API

[Estebanrg21]

Summary

This pull request implements the Suzuki-Trotter evolution within the C API.

Details and comments

1. New APIs:

• The file with the implementation for the Suzuki-Trotter evolution at crates/circuit_library/src/suzuki_trotter.rs
• The file with the implementation for the Suzuki-Trotter evolution at crates/synthesis/src/evolution/suzuki_trotter.rs
• The file with the exposure of the Suzuki-Trotter evolution for the C API at crates/cext/src/synthesis/suzuki_trotter.rs

2. As part of the implementation, some APIs were made public:

• modulesynthesis/evolution
• Instruction struct from crates/circuit_library/src/pauli_evolution.rs
• module crates/circuit_library/src/pauli_evolution.rs

3. The qiskit-synthesis and qiskit-quantum-info crates were added as dependencies for qiskit-circuit-library

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[Cryoris]

Thanks for the PR @Estebanrg21, this already looks pretty good! I think we can improve the datastructures a bit and avoid some clones and collections.

This would also need a release note 🙂

[Cryoris]

You don't have to collect this into a vec if you're just iterating over it later, i.e, we can do

let mut graph = ..
for term in terms.iter().sorted_by_key(..) {
  graph.add_node(term);
}

[Estebanrg21]

I did some changes in ba99114. Here this iteration cannot be done just once because sorted is used in other parts of the code. Should I still refactor it?

[Cryoris]

Is there a way to tell the graph what capacity we need, such that we can allocate the required memory only one?

[Estebanrg21]

On ba99114 I used the function like this:

Graph::with_capacity(sorted.len(), edges.len())

Would that be enough?

[Cryoris]

This function does a lot of collecting and cloning, that we should try to avoid. We could change e.g. to return the indices in which the terms should be applied instead of cloning and collecting into a new container.

[Estebanrg21]

I refactored the code in ba99114 to only have the collection of terms in the sorted variable. I believe now it's avoided most of the collecting and cloning present before. What do you think?

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[coveralls]

Pull Request Test Coverage Report for Build 20451425357

Details

• 18 of 194 (9.28%) changed or added relevant lines in 3 files are covered.
• 4 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.1%) to 88.191%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
crates/circuit_library/src/suzuki_trotter.rs	0	82	0.0%
crates/synthesis/src/evolution/suzuki_trotter.rs	0	94	0.0%

Files with Coverage Reduction	New Missed Lines	%
crates/circuit/src/parameter/parameter_expression.rs	1	82.3%
crates/qasm2/src/lex.rs	3	92.29%

Totals
Change from base Build 20366546417:	-0.1%
Covered Lines:	96755
Relevant Lines:	109711

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💛 - Coveralls