Unitary Layer RB (#1561)

This PR adds a new class to do layer style RB with an arbitrary set of
2Q unitary circuits for the entangling layer. Example usage which will
perform RB with 10 different RZZ angles.

```
rzz_gate_lst = []

for i in range(10):

    qc = QuantumCircuit(2)
    qc.rzz(np.pi/2/10*(i+1),0,1)
    print(np.pi/2/10*(i+1))

    rzz_gate_lst.append(qc.to_instruction())


rb_obj = LayerFidelityUnitary(physical_qubits = [0,1,2,3], 
                              two_qubit_layers = [[[0,1],[2,3]]], 
                              two_qubit_gates=rzz_gate_lst, 
                              lengths = [2,10,100], backend=backend, num_samples=1, seed=1, layer_barrier=False)

```

---------

Co-authored-by: Will Shanks <[email protected]>

Author: dcmckayibm

qiskit_experiments/library/__init__.py

@@ -37,6 +37,7 @@
     ~randomized_benchmarking.StandardRB
     ~randomized_benchmarking.InterleavedRB
     ~randomized_benchmarking.LayerFidelity
+    ~randomized_benchmarking.LayerFidelityUnitary
     ~tomography.TomographyExperiment
     ~tomography.StateTomography
     ~tomography.ProcessTomography
@@ -121,7 +122,12 @@
     ZZRamsey,
     MultiStateDiscrimination,
 )
-from .randomized_benchmarking import StandardRB, InterleavedRB
+from .randomized_benchmarking import (
+    StandardRB,
+    InterleavedRB,
+    LayerFidelity,
+    LayerFidelityUnitary,
+)
 from .tomography import (
     TomographyExperiment,
     StateTomography,

qiskit_experiments/library/randomized_benchmarking/__init__.py

@@ -26,6 +26,7 @@
     StandardRB
     InterleavedRB
     LayerFidelity
+    LayerFidelityUnitary
 
 
 Analysis
@@ -64,4 +65,5 @@
 from .rb_utils import RBUtils
 from .clifford_synthesis import RBDefaultCliffordSynthesis
 from .layer_fidelity import LayerFidelity
+from .layer_fidelity_unitary import LayerFidelityUnitary
 from .layer_fidelity_analysis import LayerFidelityAnalysis

qiskit_experiments/library/randomized_benchmarking/clifford_utils.py

@@ -55,13 +55,17 @@ def _transpile_clifford_circuit(
     return _apply_qubit_layout(_decompose_clifford_ops(circuit), physical_qubits=physical_qubits)
 
 
-def _decompose_clifford_ops(circuit: QuantumCircuit) -> QuantumCircuit:
-    # Simplified QuantumCircuit.decompose, which decomposes only Clifford ops
+def _decompose_clifford_ops(circuit: QuantumCircuit, all_circs: bool = False) -> QuantumCircuit:
+    # Simplified QuantumCircuit.decompose, which decomposes Clifford
+    # ops into the underlying circuit elements. If all_circs is True then this will
+    # also decompose operations starting with "circuit"
     res = circuit.copy_empty_like()
     if hasattr(circuit, "_parameter_table"):
         res._parameter_table = circuit._parameter_table
     for inst in circuit:
-        if inst.operation.name.startswith("Clifford"):  # Decompose
+        if inst.operation.name.startswith("Clifford") or (
+            all_circs and inst.operation.name.startswith("circuit")
+        ):  # Decompose
             rule = inst.operation.definition.data
             if len(rule) == 1 and len(inst.qubits) == len(rule[0].qubits):
                 if inst.operation.definition.global_phase:

qiskit_experiments/library/randomized_benchmarking/layer_fidelity.py

@@ -347,21 +347,22 @@ def __validate_basis_gates(self) -> None:
         if not self.backend:
             return
         opts = self.experiment_options
+        target = self.backend.target
         # validate two_qubit_gate if it is set
         if opts.two_qubit_gate:
-            if opts.two_qubit_gate not in self.backend.target.operation_names:
+            if opts.two_qubit_gate not in target.operation_names:
                 raise QiskitError(f"two_qubit_gate {opts.two_qubit_gate} is not in backend.target")
             for two_q_layer in opts.two_qubit_layers:
                 for qpair in two_q_layer:
-                    if not self.backend.target.instruction_supported(opts.two_qubit_gate, qpair):
+                    if not target.instruction_supported(opts.two_qubit_gate, qpair):
                         raise QiskitError(f"{opts.two_qubit_gate}{qpair} is not in backend.target")
         # validate one_qubit_basis_gates if it is set
         for gate in opts.one_qubit_basis_gates or []:
-            if gate not in self.backend.target.operation_names:
+            if gate not in target.operation_names:
                 raise QiskitError(f"{gate} in one_qubit_basis_gates is not in backend.target")
         for gate in opts.one_qubit_basis_gates or []:
             for q in self.physical_qubits:
-                if not self.backend.target.instruction_supported(gate, (q,)):
+                if not target.instruction_supported(gate, (q,)):
                     raise QiskitError(f"{gate}({q}) is not in backend.target")
 
     def __residual_qubits(self, two_qubit_layer):