From 8e223fab275953867e9df39468d99b58d29cc310 Mon Sep 17 00:00:00 2001
From: mhucka <1450019+mhucka@users.noreply.github.com>
Date: Sun, 12 Apr 2026 04:20:21 +0000
Subject: [PATCH] Optimize MatrixGate translation using NumPy interleaving

Replaced an inefficient nested list comprehension with a NumPy-based
approach for interleaving real and imaginary parts of unitary matrices.
This avoids thousands of small list allocations and leverages NumPy's
optimized slicing and flattening.
---
 qsimcirq/qsim_circuit.py | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/qsimcirq/qsim_circuit.py b/qsimcirq/qsim_circuit.py
index a5b4ae277..1b89cced6 100644
--- a/qsimcirq/qsim_circuit.py
+++ b/qsimcirq/qsim_circuit.py
@@ -306,9 +306,11 @@ def add_op_to_circuit(
                 time, qsim_qubits, qsim_gate._diag_angles_radians, circuit
             )
     elif gate_kind == qsim.kMatrixGate:
-        m = [
-            val for i in list(cirq.unitary(qsim_gate).flat) for val in [i.real, i.imag]
-        ]
+        unitary = cirq.unitary(qsim_gate)
+        m = np.empty(unitary.size * 2, dtype=np.float64)
+        m[0::2] = unitary.real.flat
+        m[1::2] = unitary.imag.flat
+        m = m.tolist()
         if isinstance(circuit, qsim.Circuit):
             qsim.add_matrix_gate(time, qsim_qubits, m, circuit)
         else: