diff --git a/src/circuit_json.rs b/src/circuit_json.rs
index 9e50fb5..60d44a7 100644
--- a/src/circuit_json.rs
+++ b/src/circuit_json.rs
@@ -40,7 +40,7 @@ pub struct Bitstring {
 /// A 2D matrix.
 #[derive(Deserialize, Serialize, Clone, Debug, PartialEq, Eq, Hash)]
 #[serde(transparent)]
-pub struct Matrix<T = f32> {
+pub struct Matrix<T = f64> {
     /// A 2D vector of complex numbers.
     pub data: Vec<Vec<(T, T)>>,
 }
diff --git a/src/opbox.rs b/src/opbox.rs
index ae8f30e..794e5a2 100644
--- a/src/opbox.rs
+++ b/src/opbox.rs
@@ -34,25 +34,25 @@ pub enum OpBox {
     Unitary1qBox {
         id: BoxID,
         /// 2x2 matrix of complex numbers
-        matrix: [[(f32, f32); 2]; 2],
+        matrix: [[(f64, f64); 2]; 2],
     },
     /// Two-qubit operation defined as a unitary matrix.
     Unitary2qBox {
         id: BoxID,
         /// 4x4 matrix of complex numbers
-        matrix: [[(f32, f32); 4]; 4],
+        matrix: [[(f64, f64); 4]; 4],
     },
     /// Three-qubit operation defined as a unitary matrix.
     Unitary3qBox {
         id: BoxID,
         /// 8x8 matrix of complex numbers
-        matrix: Box<[[(f32, f32); 8]; 8]>,
+        matrix: Box<[[(f64, f64); 8]; 8]>,
     },
     /// Two-qubit operation defined in terms of a hermitian matrix and a phase.
     ExpBox {
         id: BoxID,
         /// 4x4 matrix of complex numbers
-        matrix: [[(f32, f32); 4]; 4],
+        matrix: [[(f64, f64); 4]; 4],
         /// Phase of the operation.
         phase: f64,
     },