From d9a2341e52a6bd3c332a34e39175b274388383b8 Mon Sep 17 00:00:00 2001
From: Boxi Li <etamin1201@gmail.com>
Date: Sun, 10 Dec 2023 23:02:53 +0100
Subject: [PATCH] Use the simulator to compute unitary

Provide qeye as the input states.
---
 src/qutip_qip/circuit/circuit.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/qutip_qip/circuit/circuit.py b/src/qutip_qip/circuit/circuit.py
index 975862d4..35fd9815 100644
--- a/src/qutip_qip/circuit/circuit.py
+++ b/src/qutip_qip/circuit/circuit.py
@@ -17,13 +17,12 @@
     Measurement,
     expand_operator,
     GATE_CLASS_MAP,
-    gate_sequence_product,
 )
 from .circuitsimulator import (
     CircuitSimulator,
     CircuitResult,
 )
-from qutip import basis, Qobj
+from qutip import Qobj, qeye
 
 
 try:
@@ -939,8 +938,9 @@ def compute_unitary(self):
         circuit_unitary : :class:`qutip.Qobj`
             Product of all gate arrays in the quantum circuit.
         """
-        gate_list = self.propagators()
-        circuit_unitary = gate_sequence_product(gate_list)
+        sim = CircuitSimulator(self)
+        result = sim.run(qeye(self.dims))
+        circuit_unitary = result.get_final_states()[0]
         return circuit_unitary
 
     def latex_code(self):