Get dtype from the set target (#2022)

* Determine precision based on the set target

* adding a test

* fixing spelling in comment

python/cudaq/runtime/state.py

@@ -5,6 +5,7 @@
 # This source code and the accompanying materials are made available under     #
 # the terms of the Apache License 2.0 which accompanies this distribution.     #
 # ============================================================================ #
+from ..mlir._mlir_libs._quakeDialects import cudaq_runtime
 
 
 def to_cupy(state, dtype=None):
@@ -17,8 +18,11 @@ def to_cupy(state, dtype=None):
     except ImportError:
         print('to_cupy not supported, CuPy not available. Please install CuPy.')
 
-    if dtype == None:
-        dtype = cp.complex64
+    if dtype is None:
+        # Determine the correct data type based on the cudaq target's precision
+        target = cudaq_runtime.get_target()
+        precision = target.get_precision()
+        dtype = cp.complex128 if precision == cudaq_runtime.SimulationPrecision.fp64 else cp.complex64
 
     if not state.is_on_gpu():
         raise RuntimeError(

python/tests/builder/test_cupy_integration.py

@@ -107,6 +107,20 @@ def test_cupy_to_state():
     assert np.isclose(result, 1.0, atol=1e-3)
 
 
+def test_cupy_to_state_without_dtype():
+    cp_data = cp.array([.707107, 0, 0, .707107])
+    state_from_cupy = cudaq.State.from_data(cp_data)
+    state_from_cupy.dump()
+    kernel = cudaq.make_kernel()
+    q = kernel.qalloc(2)
+    kernel.h(q[0])
+    kernel.cx(q[0], q[1])
+    # State is on the GPU, this is nvidia target
+    state = cudaq.get_state(kernel)
+    result = state.overlap(state_from_cupy)
+    assert np.isclose(result, 1.0, atol=1e-3)
+
+
 # leave for gdb debugging
 if __name__ == "__main__":
     loc = os.path.abspath(__file__)