Start reworking qasm parser

src/qibotn/quimb.py

@@ -0,0 +1,74 @@
+import re
+
+import qibo
+import quimb.tensor as qtn
+import numpy as np
+
+
+def get_gate_functions(qasm_str, start_idx):
+    func_list = []
+    result = []
+    idx_inc = 0
+    for line in qasm_str[start_idx:]:
+        if "gate " in line:
+            result = re.findall("[^,\s()]+", line)
+        elif result and "{" not in line and "}" not in line:
+            params = get_gate_params(line)
+            func_list.append(*params)
+        elif "}" in line:
+            print("Returning the list")
+            print(func_list)
+            return func_list, idx_inc
+        idx_inc += 1
+
+
+def convert(nqubits: int, qasm_str: str, with_swaps: bool = True, psi0=None):
+    circ = qtn.Circuit(nqubits, psi0=psi0)
+
+    qasm_str = qasm_str.split("\n")
+    for idx, line in enumerate(qasm_str):
+        command = line.split(" ")[0]
+        if re.search("include|//|OPENQASM", command):
+            continue
+        elif "qreg" in command:
+            nbits = int(re.findall(r"\d+", line)[0])
+            assert nbits == nqubits
+        elif "swap" in command:
+            break
+        elif "gate" in command:  # TODO: Complete gate handling
+            gate_func, increment = get_gate_functions(qasm_str, idx)
+            pass
+        elif "barrier" in command:  # TODO: Complete barrier handling
+            pass
+        elif "measure" in command:  # TODO: Complete measure handling
+            pass
+        else:
+            params = get_gate_params(line)
+            circ.apply_gate(*params)
+
+    if with_swaps:
+        for i in range(nqubits // 2):  # TODO: Ignore the barrier indices?
+            circ.apply_gate("SWAP", i, nqubits - i - 1)
+
+    return circ
+
+
+def init_state_tn(nqubits, init_state_sv):
+    dims = tuple(2 * np.ones(nqubits, dtype=int))
+
+    return qtn.tensor_1d.MatrixProductState.from_dense(init_state_sv, dims)
+
+
+def eval(qasm: str, init_state, backend="numpy", swaps=True):
+    """Evaluate QASM with Quimb
+
+    backend (quimb): numpy, cupy, jax. Passed to ``opt_einsum``.
+
+    """
+    circuit = qibo.models.Circuit.from_qasm(qasm)
+    init_state_mps = init_state_tn(circuit.nqubits, init_state)
+    circ_quimb = convert(circuit, swaps=swaps, psi0=init_state_mps)
+    interim = circ_quimb.psi.full_simplify(seq="DRC")
+    amplitudes = interim.to_dense(backend=backend).flatten()
+
+    return amplitudes