Oxidize UnitarySynthesis pass (Qiskit#13141)

* Inital attempt at oxidizing unitary synthesis.

* Add cacache pygates feature to accelerate

* Use sabre target to speed up preferred_direction

* Adapt code to changes in PackedInstruction

* Use target in preferred_direction

* Some cleanup

* More cleanup

* Apply inline suggestions from  Matt's code review

Co-authored-by: Matthew Treinish <[email protected]>

* Apply remaining review suggestions:

 * Fix details after applying inline suggestions
 * Keep TwoQubitWeilDecomposition attributes private. Add getter.
 * Initialize new_blocks using size hint
 * Remove basis_set as it's not used if there is a target.
 * Use ref_qubits ([PhysicalQubit; 2]) instead of wire_map (IndexMap<Qubit, Physicalqubit>)
 * Define static GOODBYE_SET as suggested
 * Use ImportOnceCell for XXDecomposer and XXEmbodiments to avoid importing in a loop.
 * Set preferred_direction without making it mutable.
 * Fix check_goodbye
 * Privatize assets
 * Use the add_global_phase method instead of the private function.
 * Add qs_decomposition to imports
 * Simplify flip_bits
 * Use NormalOperation to pass around decomposer gate and params info
 * First attempt at attaching synth circuits directly
 * Second attempt at attaching synth circuits directly
 * Use edge set for coupling map
 * Avoid exposing internals from NullableIndexMap
 * Use unitary_to_gate_sequence_inner instead of optimize_1q_gates_decomposition.
 * Use concat! in long error message.

* Use dag.apply_operation_back in 1q case. Additional cleanup.

* Don't return ref to float in two qubit decomposer.

* Use PyList as input type for coupling_edges (previous approach was innefficient)

* Avoid using UnitarySynthesisReturn type, avoid intermediate dag creation in all cases except XXDecomposer.

* Refactor appending to out_dag, remove unnecesary clones.

* Cosmetic changes. Reduce indentation.

* Squash bug

* Fix clippy

* Add qsd test

* Avoid making unnecessary variables public

* Use OperationRef instead of exposing discriminant

* Rename DAGCircuit::substitue_node to py_substitute_node

Co-authored-by: Raynel Sanchez <[email protected]>

* Restore name in Python world

* Rewrite using flatten

Co-authored-by: Raynel Sanchez <[email protected]>

* Apply suggestions from Ray's code review

Co-authored-by: Raynel Sanchez <[email protected]>

* Adjust suggestions from code review. Apply remaining feedback:

* Use circuit_to_dag from crates/circuit/converters.rs

* Simplify iteration over coupling edges

* Replace cumbersome call_method_bound with call_bound

* Apply ownership suggestion from Ray

Co-authored-by: Raynel Sanchez <[email protected]>

* Finish applying ownership suggestion from Ray

* Changes to synth_error function: remove error that wasn't handled, deal with new panic calling operation_from_name

* Undo flatten

* Fix style

* Add getters and setters for TwoQubitGateSequence, expose new, keep struct attributes private.

* Apply Ray's suggestion to use unwrap_operation

Co-authored-by: Raynel Sanchez <[email protected]>

* Use ExtraInstructionAttributes::default()

* Apply suggestion to avoid intermediate collection

* Use target::contains_key

* Apply suggestion to use iter() instead of keys()

Co-authored-by: Raynel Sanchez <[email protected]>

* Final touches

* Final touches

* Replace panics with unreachable

* Format

* Apply suggestions from Matt's code review

Co-authored-by: Matthew Treinish <[email protected]>

* Fix suggestions from Matt's code review

* Apply remaining suggestions

* Apply final suggestions from code review

* Lint: Use `unwrap_or_default()`.

---------

Co-authored-by: Matthew Treinish <[email protected]>
Co-authored-by: Raynel Sanchez <[email protected]>

crates/accelerate/src/euler_one_qubit_decomposer.rs

@@ -581,7 +581,7 @@ pub fn generate_circuit(
 
 const EULER_BASIS_SIZE: usize = 12;
 
-static EULER_BASES: [&[&str]; EULER_BASIS_SIZE] = [
+pub static EULER_BASES: [&[&str]; EULER_BASIS_SIZE] = [
     &["u3"],
     &["u3", "u2", "u1"],
     &["u"],
@@ -595,7 +595,7 @@ static EULER_BASES: [&[&str]; EULER_BASIS_SIZE] = [
     &["rz", "sx", "x"],
     &["rz", "sx"],
 ];
-static EULER_BASIS_NAMES: [EulerBasis; EULER_BASIS_SIZE] = [
+pub static EULER_BASIS_NAMES: [EulerBasis; EULER_BASIS_SIZE] = [
     EulerBasis::U3,
     EulerBasis::U321,
     EulerBasis::U,

crates/accelerate/src/lib.rs

@@ -48,6 +48,7 @@ pub mod synthesis;
 pub mod target_transpiler;
 pub mod two_qubit_decompose;
 pub mod uc_gate;
+pub mod unitary_synthesis;
 pub mod utils;
 pub mod vf2_layout;
 

crates/accelerate/src/two_qubit_decompose.rs

@@ -510,6 +510,15 @@ pub struct TwoQubitWeylDecomposition {
 }
 
 impl TwoQubitWeylDecomposition {
+    pub fn a(&self) -> f64 {
+        self.a
+    }
+    pub fn b(&self) -> f64 {
+        self.b
+    }
+    pub fn c(&self) -> f64 {
+        self.c
+    }
     fn weyl_gate(
         &self,
         simplify: bool,
@@ -1231,17 +1240,39 @@ impl TwoQubitWeylDecomposition {
 
 type TwoQubitSequenceVec = Vec<(Option<StandardGate>, SmallVec<[f64; 3]>, SmallVec<[u8; 2]>)>;
 
+#[derive(Clone, Debug)]
 #[pyclass(sequence)]
 pub struct TwoQubitGateSequence {
     gates: TwoQubitSequenceVec,
     #[pyo3(get)]
     global_phase: f64,
 }
 
+impl TwoQubitGateSequence {
+    pub fn gates(&self) -> &TwoQubitSequenceVec {
+        &self.gates
+    }
+
+    pub fn global_phase(&self) -> f64 {
+        self.global_phase
+    }
+
+    pub fn set_state(&mut self, state: (TwoQubitSequenceVec, f64)) {
+        self.gates = state.0;
+        self.global_phase = state.1;
+    }
+}
+
+impl Default for TwoQubitGateSequence {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 #[pymethods]
 impl TwoQubitGateSequence {
     #[new]
-    fn new() -> Self {
+    pub fn new() -> Self {
         TwoQubitGateSequence {
             gates: Vec::new(),
             global_phase: 0.,
@@ -1273,6 +1304,8 @@ impl TwoQubitGateSequence {
         }
     }
 }
+
+#[derive(Clone, Debug)]
 #[allow(non_snake_case)]
 #[pyclass(module = "qiskit._accelerate.two_qubit_decompose", subclass)]
 pub struct TwoQubitBasisDecomposer {
@@ -1660,7 +1693,7 @@ impl TwoQubitBasisDecomposer {
         Ok(res)
     }
 
-    fn new_inner(
+    pub fn new_inner(
         gate: String,
         gate_matrix: ArrayView2<Complex64>,
         basis_fidelity: f64,
@@ -1798,7 +1831,7 @@ impl TwoQubitBasisDecomposer {
         })
     }
 
-    fn call_inner(
+    pub fn call_inner(
         &self,
         unitary: ArrayView2<Complex64>,
         basis_fidelity: Option<f64>,