diff --git a/tket-qsystem/Cargo.toml b/tket-qsystem/Cargo.toml
index 0bd978448..61159ef09 100644
--- a/tket-qsystem/Cargo.toml
+++ b/tket-qsystem/Cargo.toml
@@ -45,6 +45,9 @@ typetag.workspace = true
 delegate.workspace = true
 indexmap.workspace = true
 anyhow = { workspace = true, optional = true }
+tket1-passes = { path = "../tket1-passes" }
+rayon.workspace = true
+serde_json.workspace = true
 
 [dev-dependencies]
 cool_asserts.workspace = true
diff --git a/tket-qsystem/src/lib.rs b/tket-qsystem/src/lib.rs
index bdcf889cd..6208f18ee 100644
--- a/tket-qsystem/src/lib.rs
+++ b/tket-qsystem/src/lib.rs
@@ -24,8 +24,13 @@ use hugr_passes::{
 use std::collections::HashSet;
 
 use lower_drops::LowerDropsPass;
+use pytket::qsystem_decoder_config;
+use rayon::iter::ParallelIterator;
 use replace_bools::{ReplaceBoolPass, ReplaceBoolPassError};
+use std::sync::Arc;
 use tket::TketOp;
+use tket::serialize::pytket::{EncodeOptions, EncodedCircuit};
+use tket1_passes::{Tket1Circuit, Tket1Pass};
 
 use extension::{
     futures::FutureOpDef,
@@ -152,6 +157,34 @@ impl QSystemPass {
         }
         // restore the entrypoint
         hugr.set_entrypoint(entrypoint);
+
+        // Squash single qubit gates after conversion to the Qsystem gate set.
+        // Call the SquashRzPhasedX pass from pytket using the pass JSON
+        // https://docs.quantinuum.com/tket/api-docs/passes.html#pytket.passes.SquashRzPhasedX
+        let squash_pass_json_string =
+            serde_json::to_string(&tket_json_rs::pass::BasePass::StandardPass {
+                pass: tket_json_rs::pass::standard::StandardPass::SquashRzPhasedX,
+            })
+            .unwrap();
+        let mut encoded =
+            EncodedCircuit::new(hugr, EncodeOptions::new().with_subcircuits(true)).unwrap();
+        encoded
+            .par_iter_mut()
+            .for_each(|(_region, serial_circuit)| {
+                let mut circuit_ptr = Tket1Circuit::from_serial_circuit(serial_circuit).unwrap();
+                let my_circuit_json_before = serde_json::to_value(&serial_circuit).unwrap();
+                println!("Circuit before ============================={_region}");
+                println!("{}", my_circuit_json_before);
+                Tket1Pass::run_from_json(&squash_pass_json_string, &mut circuit_ptr).unwrap();
+                *serial_circuit = circuit_ptr.to_serial_circuit().unwrap();
+
+                let my_circuit_json_after = serde_json::to_value(&serial_circuit).unwrap();
+                println!("Circuit after =============================={_region}");
+                println!("{}", my_circuit_json_after)
+            });
+        encoded
+            .reassemble_inplace(hugr, Some(Arc::new(qsystem_decoder_config())))
+            .unwrap();
         Ok(())
     }
 
@@ -298,7 +331,7 @@ mod test {
             .finish_with_outputs([])
             .unwrap();
 
-        let (mut hugr, [call_node, h_node, f_node, rx_node, main_node]) = {
+        let (mut hugr, [call_node, h_node, f_node, rz_node, main_node]) = {
             let mut builder = mb
                 .define_function(
                     "main",
@@ -327,7 +360,7 @@ mod test {
                 .add_dataflow_op(QSystemOp::Rz, [qb, angle])
                 .unwrap()
                 .outputs_arr();
-            let rx_node = qb.node();
+            let rz_node = qb.node();
 
             // the Measure node will be removed. A Lazy Measure and two Future
             // Reads will be added.  The Lazy Measure will be lifted and the
@@ -342,7 +375,7 @@ mod test {
                 .unwrap()
                 .node();
             let hugr = mb.finish_hugr().unwrap();
-            (hugr, [call_node, h_node, f_node, rx_node, main_n])
+            (hugr, [call_node, h_node, f_node, rz_node, main_n])
         };
         if set_entrypoint {
             // set the entrypoint to the main function
@@ -362,7 +395,7 @@ mod test {
         };
         assert!(get_pos(h_node) < get_pos(f_node));
         assert!(get_pos(h_node) < get_pos(call_node));
-        assert!(get_pos(rx_node) < get_pos(call_node));
+        assert!(get_pos(rz_node) < get_pos(call_node));
 
         for n in topo_sorted
             .iter()