diff --git a/pytket/extensions/cutensornet/general.py b/pytket/extensions/cutensornet/general.py
index 97abf081..f39ed406 100644
--- a/pytket/extensions/cutensornet/general.py
+++ b/pytket/extensions/cutensornet/general.py
@@ -18,7 +18,7 @@
 def set_logger(
     logger_name: str,
     level: int = logging.WARNING,
-    fmt: str = "[%(asctime)s] %(name)s (%(levelname)s) - %(message)s",
+    fmt: str = "[%(asctime)s.%(msecs)03d] %(name)s (%(levelname)s) - %(message)s",
 ) -> Logger:
     """Initialises and configures a logger object.