diff --git a/Cargo.lock b/Cargo.lock
index 295ba5c4..1797a4b6 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -288,9 +288,9 @@ dependencies = [
 
 [[package]]
 name = "clap-verbosity-flag"
-version = "3.0.1"
+version = "2.2.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "54381ae56ad222eea3f529c692879e9c65e07945ae48d3dc4d1cb18dbec8cf44"
+checksum = "34c77f67047557f62582784fd7482884697731b2932c7d37ced54bce2312e1e2"
 dependencies = [
  "clap",
  "log",
@@ -317,7 +317,7 @@ dependencies = [
  "heck",
  "proc-macro2",
  "quote",
- "syn 2.0.89",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -539,7 +539,7 @@ checksum = "bc2323e10c92e1cf4d86e11538512e6dc03ceb586842970b6332af3d4046a046"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.89",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -561,7 +561,7 @@ dependencies = [
  "proc-macro2",
  "quote",
  "rustc_version",
- "syn 2.0.89",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -581,7 +581,7 @@ checksum = "cb7330aeadfbe296029522e6c40f315320aba36fc43a5b3632f3795348f3bd22"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.89",
+ "syn 2.0.90",
  "unicode-xid",
 ]
 
@@ -603,7 +603,7 @@ checksum = "97369cbbc041bc366949bc74d34658d6cda5621039731c6310521892a3a20ae0"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.89",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -627,7 +627,7 @@ dependencies = [
  "once_cell",
  "proc-macro2",
  "quote",
- "syn 2.0.89",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -739,7 +739,7 @@ checksum = "162ee34ebcb7c64a8abebc059ce0fee27c2262618d7b60ed8faf72fef13c3650"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.89",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -858,7 +858,7 @@ dependencies = [
 [[package]]
 name = "hugr"
 version = "0.13.3"
-source = "git+https://github.com/CQCL/hugr.git#163b211cfb8b87a7b0a6a12c8141217e0c052dd5"
+source = "git+https://github.com/CQCL/hugr.git?rev=7177c5f26c2ddf506d9987c84cf1899275d391d6#7177c5f26c2ddf506d9987c84cf1899275d391d6"
 dependencies = [
  "hugr-core",
  "hugr-passes",
@@ -867,7 +867,7 @@ dependencies = [
 [[package]]
 name = "hugr-cli"
 version = "0.13.3"
-source = "git+https://github.com/CQCL/hugr.git#163b211cfb8b87a7b0a6a12c8141217e0c052dd5"
+source = "git+https://github.com/CQCL/hugr.git?rev=7177c5f26c2ddf506d9987c84cf1899275d391d6#7177c5f26c2ddf506d9987c84cf1899275d391d6"
 dependencies = [
  "clap",
  "clap-verbosity-flag",
@@ -882,7 +882,7 @@ dependencies = [
 [[package]]
 name = "hugr-core"
 version = "0.13.3"
-source = "git+https://github.com/CQCL/hugr.git#163b211cfb8b87a7b0a6a12c8141217e0c052dd5"
+source = "git+https://github.com/CQCL/hugr.git?rev=7177c5f26c2ddf506d9987c84cf1899275d391d6#7177c5f26c2ddf506d9987c84cf1899275d391d6"
 dependencies = [
  "bitvec",
  "bumpalo",
@@ -914,7 +914,7 @@ dependencies = [
 [[package]]
 name = "hugr-passes"
 version = "0.13.3"
-source = "git+https://github.com/CQCL/hugr.git#163b211cfb8b87a7b0a6a12c8141217e0c052dd5"
+source = "git+https://github.com/CQCL/hugr.git?rev=7177c5f26c2ddf506d9987c84cf1899275d391d6#7177c5f26c2ddf506d9987c84cf1899275d391d6"
 dependencies = [
  "hugr-core",
  "itertools 0.13.0",
@@ -1062,7 +1062,7 @@ checksum = "1ec89e9337638ecdc08744df490b221a7399bf8d164eb52a665454e60e075ad6"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.89",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -1188,10 +1188,11 @@ dependencies = [
 
 [[package]]
 name = "js-sys"
-version = "0.3.72"
+version = "0.3.74"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6a88f1bda2bd75b0452a14784937d796722fdebfe50df998aeb3f0b7603019a9"
+checksum = "a865e038f7f6ed956f788f0d7d60c541fff74c7bd74272c5d4cf15c63743e705"
 dependencies = [
+ "once_cell",
  "wasm-bindgen",
 ]
 
@@ -1422,7 +1423,7 @@ dependencies = [
  "pest_meta",
  "proc-macro2",
  "quote",
- "syn 2.0.89",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -1626,7 +1627,7 @@ dependencies = [
  "proc-macro2",
  "pyo3-macros-backend",
  "quote",
- "syn 2.0.89",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -1639,7 +1640,7 @@ dependencies = [
  "proc-macro2",
  "pyo3-build-config",
  "quote",
- "syn 2.0.89",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -1770,7 +1771,7 @@ dependencies = [
  "regex",
  "relative-path",
  "rustc_version",
- "syn 2.0.89",
+ "syn 2.0.90",
  "unicode-ident",
 ]
 
@@ -1849,7 +1850,7 @@ checksum = "ad1e866f866923f252f05c889987993144fb74e722403468a4ebd70c3cd756c0"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.89",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -1949,7 +1950,7 @@ dependencies = [
  "proc-macro2",
  "quote",
  "rustversion",
- "syn 2.0.89",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -1965,9 +1966,9 @@ dependencies = [
 
 [[package]]
 name = "syn"
-version = "2.0.89"
+version = "2.0.90"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "44d46482f1c1c87acd84dea20c1bf5ebff4c757009ed6bf19cfd36fb10e92c4e"
+checksum = "919d3b74a5dd0ccd15aeb8f93e7006bd9e14c295087c9896a110f490752bcf31"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -1982,7 +1983,7 @@ checksum = "c8af7666ab7b6390ab78131fb5b0fce11d6b7a6951602017c35fa82800708971"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.89",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -2036,7 +2037,7 @@ checksum = "4fee6c4efc90059e10f81e6d42c60a18f76588c3d74cb83a0b242a2b6c7504c1"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.89",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -2047,7 +2048,7 @@ checksum = "f077553d607adc1caf65430528a576c757a71ed73944b66ebb58ef2bbd243568"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.89",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -2279,7 +2280,7 @@ checksum = "395ae124c09f9e6918a2310af6038fba074bcf474ac352496d5910dd59a2226d"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.89",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -2350,7 +2351,7 @@ checksum = "70b20a22c42c8f1cd23ce5e34f165d4d37038f5b663ad20fb6adbdf029172483"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.89",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -2451,9 +2452,9 @@ dependencies = [
 
 [[package]]
 name = "wasm-bindgen"
-version = "0.2.95"
+version = "0.2.97"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "128d1e363af62632b8eb57219c8fd7877144af57558fb2ef0368d0087bddeb2e"
+checksum = "d15e63b4482863c109d70a7b8706c1e364eb6ea449b201a76c5b89cedcec2d5c"
 dependencies = [
  "cfg-if",
  "once_cell",
@@ -2462,24 +2463,24 @@ dependencies = [
 
 [[package]]
 name = "wasm-bindgen-backend"
-version = "0.2.95"
+version = "0.2.97"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cb6dd4d3ca0ddffd1dd1c9c04f94b868c37ff5fac97c30b97cff2d74fce3a358"
+checksum = "8d36ef12e3aaca16ddd3f67922bc63e48e953f126de60bd33ccc0101ef9998cd"
 dependencies = [
  "bumpalo",
  "log",
  "once_cell",
  "proc-macro2",
  "quote",
- "syn 2.0.89",
+ "syn 2.0.90",
  "wasm-bindgen-shared",
 ]
 
 [[package]]
 name = "wasm-bindgen-macro"
-version = "0.2.95"
+version = "0.2.97"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e79384be7f8f5a9dd5d7167216f022090cf1f9ec128e6e6a482a2cb5c5422c56"
+checksum = "705440e08b42d3e4b36de7d66c944be628d579796b8090bfa3471478a2260051"
 dependencies = [
  "quote",
  "wasm-bindgen-macro-support",
@@ -2487,28 +2488,28 @@ dependencies = [
 
 [[package]]
 name = "wasm-bindgen-macro-support"
-version = "0.2.95"
+version = "0.2.97"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "26c6ab57572f7a24a4985830b120de1594465e5d500f24afe89e16b4e833ef68"
+checksum = "98c9ae5a76e46f4deecd0f0255cc223cfa18dc9b261213b8aa0c7b36f61b3f1d"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.89",
+ "syn 2.0.90",
  "wasm-bindgen-backend",
  "wasm-bindgen-shared",
 ]
 
 [[package]]
 name = "wasm-bindgen-shared"
-version = "0.2.95"
+version = "0.2.97"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "65fc09f10666a9f147042251e0dda9c18f166ff7de300607007e96bdebc1068d"
+checksum = "6ee99da9c5ba11bd675621338ef6fa52296b76b83305e9b6e5c77d4c286d6d49"
 
 [[package]]
 name = "web-sys"
-version = "0.3.72"
+version = "0.3.74"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f6488b90108c040df0fe62fa815cbdee25124641df01814dd7282749234c6112"
+checksum = "a98bc3c33f0fe7e59ad7cd041b89034fa82a7c2d4365ca538dda6cdaf513863c"
 dependencies = [
  "js-sys",
  "wasm-bindgen",
@@ -2785,7 +2786,7 @@ checksum = "2380878cad4ac9aac1e2435f3eb4020e8374b5f13c296cb75b4620ff8e229154"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.89",
+ "syn 2.0.90",
  "synstructure",
 ]
 
@@ -2806,7 +2807,7 @@ checksum = "595eed982f7d355beb85837f651fa22e90b3c044842dc7f2c2842c086f295808"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.89",
+ "syn 2.0.90",
  "synstructure",
 ]
 
@@ -2829,7 +2830,7 @@ checksum = "6eafa6dfb17584ea3e2bd6e76e0cc15ad7af12b09abdd1ca55961bed9b1063c6"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.89",
+ "syn 2.0.90",
 ]
 
 [[package]]
diff --git a/Cargo.toml b/Cargo.toml
index d29acbb7..e2e74311 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -26,9 +26,9 @@ missing_docs = "warn"
 [patch.crates-io]
 
 # Uncomment to use unreleased versions of hugr
-hugr-core = { git = "https://github.com/CQCL/hugr.git" }
-hugr = { git = "https://github.com/CQCL/hugr.git" }
-hugr-cli = { git = "https://github.com/CQCL/hugr.git" }
+hugr-core = { git = "https://github.com/CQCL/hugr.git" , rev = "7177c5f26c2ddf506d9987c84cf1899275d391d6"}
+hugr = { git = "https://github.com/CQCL/hugr.git" , rev = "7177c5f26c2ddf506d9987c84cf1899275d391d6"}
+hugr-cli = { git = "https://github.com/CQCL/hugr.git" , rev = "7177c5f26c2ddf506d9987c84cf1899275d391d6"}
 
 [workspace.dependencies]
 
diff --git a/tket2-exts/src/tket2_exts/__init__.py b/tket2-exts/src/tket2_exts/__init__.py
index 4b5ab1b8..54df9d83 100644
--- a/tket2-exts/src/tket2_exts/__init__.py
+++ b/tket2-exts/src/tket2_exts/__init__.py
@@ -17,8 +17,8 @@ def futures() -> Extension:
 
 
 @functools.cache
-def hseries() -> Extension:
-    return load_extension("tket2.hseries")
+def qsystem() -> Extension:
+    return load_extension("tket2.qsystem")
 
 
 @functools.cache
diff --git a/tket2-exts/src/tket2_exts/data/tket2/hseries.json b/tket2-exts/src/tket2_exts/data/tket2/qsystem.json
similarity index 93%
rename from tket2-exts/src/tket2_exts/data/tket2/hseries.json
rename to tket2-exts/src/tket2_exts/data/tket2/qsystem.json
index 5636f319..abdc1aec 100644
--- a/tket2-exts/src/tket2_exts/data/tket2/hseries.json
+++ b/tket2-exts/src/tket2_exts/data/tket2/qsystem.json
@@ -1,6 +1,6 @@
 {
   "version": "0.2.0",
-  "name": "tket2.hseries",
+  "name": "tket2.qsystem",
   "extension_reqs": [
     "arithmetic.float.types",
     "prelude",
@@ -10,7 +10,7 @@
   "values": {},
   "operations": {
     "LazyMeasure": {
-      "extension": "tket2.hseries",
+      "extension": "tket2.qsystem",
       "name": "LazyMeasure",
       "description": "Lazily measure a qubit and lose it.",
       "signature": {
@@ -48,7 +48,7 @@
       "binary": false
     },
     "Measure": {
-      "extension": "tket2.hseries",
+      "extension": "tket2.qsystem",
       "name": "Measure",
       "description": "Measure a qubit and lose it.",
       "signature": {
@@ -72,7 +72,7 @@
       "binary": false
     },
     "MeasureReset": {
-      "extension": "tket2.hseries",
+      "extension": "tket2.qsystem",
       "name": "MeasureReset",
       "description": "Measure a qubit and reset it to the Z |0> eigenstate.",
       "signature": {
@@ -99,7 +99,7 @@
       "binary": false
     },
     "PhasedX": {
-      "extension": "tket2.hseries",
+      "extension": "tket2.qsystem",
       "name": "PhasedX",
       "description": "PhasedX gate.",
       "signature": {
@@ -135,7 +135,7 @@
       "binary": false
     },
     "QFree": {
-      "extension": "tket2.hseries",
+      "extension": "tket2.qsystem",
       "name": "QFree",
       "description": "Free a qubit (lose track of it).",
       "signature": {
@@ -153,7 +153,7 @@
       "binary": false
     },
     "Reset": {
-      "extension": "tket2.hseries",
+      "extension": "tket2.qsystem",
       "name": "Reset",
       "description": "Reset a qubit to the Z |0> eigenstate.",
       "signature": {
@@ -175,7 +175,7 @@
       "binary": false
     },
     "Rz": {
-      "extension": "tket2.hseries",
+      "extension": "tket2.qsystem",
       "name": "Rz",
       "description": "Rotate a qubit around the Z axis. Not physical.",
       "signature": {
@@ -204,7 +204,7 @@
       "binary": false
     },
     "TryQAlloc": {
-      "extension": "tket2.hseries",
+      "extension": "tket2.qsystem",
       "name": "TryQAlloc",
       "description": "Allocate a qubit in the Z |0> eigenstate.",
       "signature": {
@@ -231,7 +231,7 @@
       "binary": false
     },
     "ZZMax": {
-      "extension": "tket2.hseries",
+      "extension": "tket2.qsystem",
       "name": "ZZMax",
       "description": "Maximally entangling ZZ gate.",
       "signature": {
@@ -259,7 +259,7 @@
       "binary": false
     },
     "ZZPhase": {
-      "extension": "tket2.hseries",
+      "extension": "tket2.qsystem",
       "name": "ZZPhase",
       "description": "ZZ gate with an angle.",
       "signature": {
diff --git a/tket2-hseries/README.md b/tket2-hseries/README.md
index e195e8e4..7f7bc2cf 100644
--- a/tket2-hseries/README.md
+++ b/tket2-hseries/README.md
@@ -3,7 +3,7 @@
 ![msrv][]
 
 A TKET2 tool for preparing and validating `Hugr`s for compilation targeting
-Quantinuum H-series  quantum computers.
+Quantinuum System  quantum computers.
 
 ## Usage
 
diff --git a/tket2-hseries/src/bin/tket2-hseries.rs b/tket2-hseries/src/bin/tket2-hseries.rs
index a16a1cf9..5556ac45 100644
--- a/tket2-hseries/src/bin/tket2-hseries.rs
+++ b/tket2-hseries/src/bin/tket2-hseries.rs
@@ -10,7 +10,7 @@ fn main() {
             let reg = ExtensionRegistry::try_new([
                 tket2::extension::TKET2_EXTENSION.to_owned(),
                 tket2::extension::rotation::ROTATION_EXTENSION.to_owned(),
-                tket2_hseries::extension::hseries::EXTENSION.to_owned(),
+                tket2_hseries::extension::qsystem::EXTENSION.to_owned(),
                 tket2_hseries::extension::futures::EXTENSION.to_owned(),
                 tket2_hseries::extension::result::EXTENSION.to_owned(),
             ])
diff --git a/tket2-hseries/src/extension.rs b/tket2-hseries/src/extension.rs
index a888e2be..68b0eee3 100644
--- a/tket2-hseries/src/extension.rs
+++ b/tket2-hseries/src/extension.rs
@@ -1,4 +1,4 @@
 //! This module defines the Hugr extensions used by tket2-hseries.
 pub mod futures;
-pub mod hseries;
+pub mod qsystem;
 pub mod result;
diff --git a/tket2-hseries/src/extension/hseries.rs b/tket2-hseries/src/extension/qsystem.rs
similarity index 80%
rename from tket2-hseries/src/extension/hseries.rs
rename to tket2-hseries/src/extension/qsystem.rs
index deb124a6..9aaab4c4 100644
--- a/tket2-hseries/src/extension/hseries.rs
+++ b/tket2-hseries/src/extension/qsystem.rs
@@ -32,15 +32,15 @@ use super::futures::future_type;
 
 mod lower;
 use lower::pi_mul_f64;
-pub use lower::{check_lowered, lower_tk2_op, LowerTk2Error, LowerTket2ToHSeriesPass};
+pub use lower::{check_lowered, lower_tk2_op, LowerTk2Error, LowerTket2ToQSystemPass};
 
-/// The "tket2.hseries" extension id.
-pub const EXTENSION_ID: ExtensionId = ExtensionId::new_unchecked("tket2.hseries");
-/// The "tket2.hseries" extension version.
+/// The "tket2.qsystem" extension id.
+pub const EXTENSION_ID: ExtensionId = ExtensionId::new_unchecked("tket2.qsystem");
+/// The "tket2.qsystem" extension version.
 pub const EXTENSION_VERSION: Version = Version::new(0, 2, 0);
 
 lazy_static! {
-    /// The "tket2.hseries" extension.
+    /// The "tket2.qsystem" extension.
     pub static ref EXTENSION: Arc<Extension> = {
          Extension::new_arc(EXTENSION_ID, EXTENSION_VERSION, |ext, ext_ref| {
             ext.add_requirements(ExtensionSet::from_iter([
@@ -48,11 +48,11 @@ lazy_static! {
                 PRELUDE.name(),
                 FLOAT_TYPES.name(),
             ].into_iter().cloned()));
-            HSeriesOp::load_all_ops( ext, ext_ref).unwrap();
+            QSystemOp::load_all_ops( ext, ext_ref).unwrap();
         })
     };
 
-    /// Extension registry including the "tket2.hseries" extension and
+    /// Extension registry including the "tket2.qsystem" extension and
     /// dependencies.
     pub static ref REGISTRY: ExtensionRegistry = ExtensionRegistry::try_new([
         EXTENSION.to_owned(),
@@ -79,7 +79,7 @@ lazy_static! {
 )]
 #[allow(missing_docs)]
 #[non_exhaustive]
-pub enum HSeriesOp {
+pub enum QSystemOp {
     Measure,
     LazyMeasure,
     Rz,
@@ -92,9 +92,9 @@ pub enum HSeriesOp {
     MeasureReset,
 }
 
-impl MakeOpDef for HSeriesOp {
+impl MakeOpDef for QSystemOp {
     fn signature(&self) -> SignatureFunc {
-        use HSeriesOp::*;
+        use QSystemOp::*;
         let one_qb_row = type_row![QB_T];
         let two_qb_row = type_row![QB_T, QB_T];
         match self {
@@ -122,22 +122,22 @@ impl MakeOpDef for HSeriesOp {
 
     fn description(&self) -> String {
         match self {
-            HSeriesOp::Measure => "Measure a qubit and lose it.",
-            HSeriesOp::LazyMeasure => "Lazily measure a qubit and lose it.",
-            HSeriesOp::Rz => "Rotate a qubit around the Z axis. Not physical.",
-            HSeriesOp::PhasedX => "PhasedX gate.",
-            HSeriesOp::ZZMax => "Maximally entangling ZZ gate.",
-            HSeriesOp::ZZPhase => "ZZ gate with an angle.",
-            HSeriesOp::TryQAlloc => "Allocate a qubit in the Z |0> eigenstate.",
-            HSeriesOp::QFree => "Free a qubit (lose track of it).",
-            HSeriesOp::Reset => "Reset a qubit to the Z |0> eigenstate.",
-            HSeriesOp::MeasureReset => "Measure a qubit and reset it to the Z |0> eigenstate.",
+            QSystemOp::Measure => "Measure a qubit and lose it.",
+            QSystemOp::LazyMeasure => "Lazily measure a qubit and lose it.",
+            QSystemOp::Rz => "Rotate a qubit around the Z axis. Not physical.",
+            QSystemOp::PhasedX => "PhasedX gate.",
+            QSystemOp::ZZMax => "Maximally entangling ZZ gate.",
+            QSystemOp::ZZPhase => "ZZ gate with an angle.",
+            QSystemOp::TryQAlloc => "Allocate a qubit in the Z |0> eigenstate.",
+            QSystemOp::QFree => "Free a qubit (lose track of it).",
+            QSystemOp::Reset => "Reset a qubit to the Z |0> eigenstate.",
+            QSystemOp::MeasureReset => "Measure a qubit and reset it to the Z |0> eigenstate.",
         }
         .to_string()
     }
 }
 
-impl MakeRegisteredOp for HSeriesOp {
+impl MakeRegisteredOp for QSystemOp {
     fn extension_id(&self) -> ExtensionId {
         EXTENSION_ID
     }
@@ -148,73 +148,73 @@ impl MakeRegisteredOp for HSeriesOp {
 }
 
 /// An extension trait for [Dataflow] providing methods to add
-/// "tket2.hseries" operations.
-pub trait HSeriesOpBuilder: Dataflow + UnwrapBuilder {
-    /// Add a "tket2.hseries.LazyMeasure" op.
+/// "tket2.qsystem" operations.
+pub trait QSystemOpBuilder: Dataflow + UnwrapBuilder {
+    /// Add a "tket2.qsystem.LazyMeasure" op.
     fn add_lazy_measure(&mut self, qb: Wire) -> Result<[Wire; 2], BuildError> {
         Ok(self
-            .add_dataflow_op(HSeriesOp::LazyMeasure, [qb])?
+            .add_dataflow_op(QSystemOp::LazyMeasure, [qb])?
             .outputs_arr())
     }
 
-    /// Add a "tket2.hseries.Measure" op.
+    /// Add a "tket2.qsystem.Measure" op.
     fn add_measure(&mut self, qb: Wire) -> Result<Wire, BuildError> {
-        Ok(self.add_dataflow_op(HSeriesOp::Measure, [qb])?.out_wire(0))
+        Ok(self.add_dataflow_op(QSystemOp::Measure, [qb])?.out_wire(0))
     }
 
-    /// Add a "tket2.hseries.Reset" op.
+    /// Add a "tket2.qsystem.Reset" op.
     fn add_reset(&mut self, qb: Wire) -> Result<Wire, BuildError> {
-        Ok(self.add_dataflow_op(HSeriesOp::Reset, [qb])?.out_wire(0))
+        Ok(self.add_dataflow_op(QSystemOp::Reset, [qb])?.out_wire(0))
     }
 
-    /// Add a "tket2.hseries.ZZMax" op.
+    /// Add a "tket2.qsystem.ZZMax" op.
     fn add_zz_max(&mut self, qb1: Wire, qb2: Wire) -> Result<[Wire; 2], BuildError> {
         Ok(self
-            .add_dataflow_op(HSeriesOp::ZZMax, [qb1, qb2])?
+            .add_dataflow_op(QSystemOp::ZZMax, [qb1, qb2])?
             .outputs_arr())
     }
 
-    /// Add a "tket2.hseries.ZZPhase" op.
+    /// Add a "tket2.qsystem.ZZPhase" op.
     fn add_zz_phase(&mut self, qb1: Wire, qb2: Wire, angle: Wire) -> Result<[Wire; 2], BuildError> {
         Ok(self
-            .add_dataflow_op(HSeriesOp::ZZPhase, [qb1, qb2, angle])?
+            .add_dataflow_op(QSystemOp::ZZPhase, [qb1, qb2, angle])?
             .outputs_arr())
     }
 
-    /// Add a "tket2.hseries.PhasedX" op.
+    /// Add a "tket2.qsystem.PhasedX" op.
     fn add_phased_x(&mut self, qb: Wire, angle1: Wire, angle2: Wire) -> Result<Wire, BuildError> {
         Ok(self
-            .add_dataflow_op(HSeriesOp::PhasedX, [qb, angle1, angle2])?
+            .add_dataflow_op(QSystemOp::PhasedX, [qb, angle1, angle2])?
             .out_wire(0))
     }
 
-    /// Add a "tket2.hseries.Rz" op.
+    /// Add a "tket2.qsystem.Rz" op.
     fn add_rz(&mut self, qb: Wire, angle: Wire) -> Result<Wire, BuildError> {
         Ok(self
-            .add_dataflow_op(HSeriesOp::Rz, [qb, angle])?
+            .add_dataflow_op(QSystemOp::Rz, [qb, angle])?
             .out_wire(0))
     }
 
-    /// Add a "tket2.hseries.TryQAlloc" op.
+    /// Add a "tket2.qsystem.TryQAlloc" op.
     fn add_try_alloc(&mut self) -> Result<Wire, BuildError> {
-        Ok(self.add_dataflow_op(HSeriesOp::TryQAlloc, [])?.out_wire(0))
+        Ok(self.add_dataflow_op(QSystemOp::TryQAlloc, [])?.out_wire(0))
     }
 
-    /// Add a "tket2.hseries.QFree" op.
+    /// Add a "tket2.qsystem.QFree" op.
     fn add_qfree(&mut self, qb: Wire) -> Result<(), BuildError> {
-        self.add_dataflow_op(HSeriesOp::QFree, [qb])?;
+        self.add_dataflow_op(QSystemOp::QFree, [qb])?;
         Ok(())
     }
 
-    /// Add a "tket2.hseries.MeasureReset" op.
+    /// Add a "tket2.qsystem.MeasureReset" op.
     /// This operation is equivalent to a `Measure` followed by a `Reset`.
     fn add_measure_reset(&mut self, qb: Wire) -> Result<[Wire; 2], BuildError> {
         Ok(self
-            .add_dataflow_op(HSeriesOp::MeasureReset, [qb])?
+            .add_dataflow_op(QSystemOp::MeasureReset, [qb])?
             .outputs_arr())
     }
 
-    /// Build a hadamard gate in terms of HSeries primitives.
+    /// Build a hadamard gate in terms of QSystem primitives.
     fn build_h(&mut self, qb: Wire) -> Result<Wire, BuildError> {
         let pi = pi_mul_f64(self, 1.0);
         let pi_2 = pi_mul_f64(self, 0.5);
@@ -224,51 +224,51 @@ pub trait HSeriesOpBuilder: Dataflow + UnwrapBuilder {
         self.add_rz(q, pi)
     }
 
-    /// Build an X gate in terms of HSeries primitives.
+    /// Build an X gate in terms of QSystem primitives.
     fn build_x(&mut self, qb: Wire) -> Result<Wire, BuildError> {
         let pi = pi_mul_f64(self, 1.0);
         let zero = pi_mul_f64(self, 0.0);
         self.add_phased_x(qb, pi, zero)
     }
 
-    /// Build a Y gate in terms of HSeries primitives.
+    /// Build a Y gate in terms of QSystem primitives.
     fn build_y(&mut self, qb: Wire) -> Result<Wire, BuildError> {
         let pi = pi_mul_f64(self, 1.0);
         let pi_2 = pi_mul_f64(self, 0.5);
         self.add_phased_x(qb, pi, pi_2)
     }
 
-    /// Build a Z gate in terms of HSeries primitives.
+    /// Build a Z gate in terms of QSystem primitives.
     fn build_z(&mut self, qb: Wire) -> Result<Wire, BuildError> {
         let pi = pi_mul_f64(self, 1.0);
         self.add_rz(qb, pi)
     }
 
-    /// Build an S gate in terms of HSeries primitives.
+    /// Build an S gate in terms of QSystem primitives.
     fn build_s(&mut self, qb: Wire) -> Result<Wire, BuildError> {
         let pi_2 = pi_mul_f64(self, 0.5);
         self.add_rz(qb, pi_2)
     }
 
-    /// Build an Sdg gate in terms of HSeries primitives.
+    /// Build an Sdg gate in terms of QSystem primitives.
     fn build_sdg(&mut self, qb: Wire) -> Result<Wire, BuildError> {
         let pi_minus_2 = pi_mul_f64(self, -0.5);
         self.add_rz(qb, pi_minus_2)
     }
 
-    /// Build a T gate in terms of HSeries primitives.
+    /// Build a T gate in terms of QSystem primitives.
     fn build_t(&mut self, qb: Wire) -> Result<Wire, BuildError> {
         let pi_4 = pi_mul_f64(self, 0.25);
         self.add_rz(qb, pi_4)
     }
 
-    /// Build a Tdg gate in terms of HSeries primitives.
+    /// Build a Tdg gate in terms of QSystem primitives.
     fn build_tdg(&mut self, qb: Wire) -> Result<Wire, BuildError> {
         let pi_minus_4 = pi_mul_f64(self, -0.25);
         self.add_rz(qb, pi_minus_4)
     }
 
-    /// Build a CNOT gate in terms of HSeries primitives.
+    /// Build a CNOT gate in terms of QSystem primitives.
     fn build_cx(&mut self, c: Wire, t: Wire) -> Result<[Wire; 2], BuildError> {
         let pi = pi_mul_f64(self, 1.0);
         let pi_2 = pi_mul_f64(self, 0.5);
@@ -283,7 +283,7 @@ pub trait HSeriesOpBuilder: Dataflow + UnwrapBuilder {
         Ok([c, t])
     }
 
-    /// Build a CY gate in terms of HSeries primitives.
+    /// Build a CY gate in terms of QSystem primitives.
     fn build_cy(&mut self, a: Wire, b: Wire) -> Result<[Wire; 2], BuildError> {
         let pi_2 = pi_mul_f64(self, 0.5);
         let pi_minus_2 = pi_mul_f64(self, -0.5);
@@ -297,7 +297,7 @@ pub trait HSeriesOpBuilder: Dataflow + UnwrapBuilder {
         Ok([a, b])
     }
 
-    /// Build a CZ gate in terms of HSeries primitives.
+    /// Build a CZ gate in terms of QSystem primitives.
     fn build_cz(&mut self, a: Wire, b: Wire) -> Result<[Wire; 2], BuildError> {
         let pi = pi_mul_f64(self, 1.0);
         let pi_2 = pi_mul_f64(self, 0.5);
@@ -312,19 +312,19 @@ pub trait HSeriesOpBuilder: Dataflow + UnwrapBuilder {
         Ok([a, b])
     }
 
-    /// Build a RX gate in terms of HSeries primitives.
+    /// Build a RX gate in terms of QSystem primitives.
     fn build_rx(&mut self, qb: Wire, theta: Wire) -> Result<Wire, BuildError> {
         let zero = pi_mul_f64(self, 0.0);
         self.add_phased_x(qb, theta, zero)
     }
 
-    /// Build a RY gate in terms of HSeries primitives.
+    /// Build a RY gate in terms of QSystem primitives.
     fn build_ry(&mut self, qb: Wire, theta: Wire) -> Result<Wire, BuildError> {
         let pi_2 = pi_mul_f64(self, 0.5);
         self.add_phased_x(qb, theta, pi_2)
     }
 
-    /// Build a CRZ gate in terms of HSeries primitives.
+    /// Build a CRZ gate in terms of QSystem primitives.
     fn build_crz(&mut self, a: Wire, b: Wire, lambda: Wire) -> Result<[Wire; 2], BuildError> {
         let two = self.add_load_const(Value::from(ConstF64::new(2.0)));
         let lambda_2 = self
@@ -339,7 +339,7 @@ pub trait HSeriesOpBuilder: Dataflow + UnwrapBuilder {
         Ok([a, b])
     }
 
-    /// Build a Toffoli (CCX) gate in terms of HSeries primitives.
+    /// Build a Toffoli (CCX) gate in terms of QSystem primitives.
     fn build_toffoli(&mut self, a: Wire, b: Wire, c: Wire) -> Result<[Wire; 3], BuildError> {
         let pi = pi_mul_f64(self, 1.0);
         let pi_2 = pi_mul_f64(self, 0.5);
@@ -401,7 +401,7 @@ pub trait HSeriesOpBuilder: Dataflow + UnwrapBuilder {
     }
 }
 
-impl<D: Dataflow> HSeriesOpBuilder for D {}
+impl<D: Dataflow> QSystemOpBuilder for D {}
 
 #[cfg(test)]
 mod test {
@@ -423,8 +423,8 @@ mod test {
     fn create_extension() {
         assert_eq!(EXTENSION.name(), &EXTENSION_ID);
 
-        for o in HSeriesOp::iter() {
-            assert_eq!(HSeriesOp::from_def(get_opdef(o).unwrap()), Ok(o));
+        for o in QSystemOp::iter() {
+            assert_eq!(QSystemOp::from_def(get_opdef(o).unwrap()), Ok(o));
         }
     }
 
@@ -471,9 +471,9 @@ mod test {
     #[test]
     fn test_cast() {
         // test overlapping names don't cause cast errors
-        for op in HSeriesOp::iter() {
+        for op in QSystemOp::iter() {
             let optype: OpType = op.into();
-            let new_op: HSeriesOp = optype.cast().unwrap();
+            let new_op: QSystemOp = optype.cast().unwrap();
             assert_eq!(op, new_op);
             assert_eq!(optype.cast::<tket2::Tk2Op>(), None);
         }
diff --git a/tket2-hseries/src/extension/hseries/lower.rs b/tket2-hseries/src/extension/qsystem/lower.rs
similarity index 85%
rename from tket2-hseries/src/extension/hseries/lower.rs
rename to tket2-hseries/src/extension/qsystem/lower.rs
index 4c5da318..452fcfa3 100644
--- a/tket2-hseries/src/extension/hseries/lower.rs
+++ b/tket2-hseries/src/extension/qsystem/lower.rs
@@ -15,13 +15,13 @@ use std::collections::HashMap;
 use strum::IntoEnumIterator;
 use tket2::{extension::rotation::RotationOpBuilder, Tk2Op};
 
-use crate::extension::hseries::{HSeriesOp, HSeriesOpBuilder};
+use crate::extension::qsystem::{self, QSystemOp, QSystemOpBuilder};
 
 lazy_static! {
-    /// Extension registry including [crate::extension::hseries::REGISTRY] and
+    /// Extension registry including [crate::extension::qsystem::REGISTRY] and
     /// [tket2::extension::rotation::ROTATION_EXTENSION].
     pub static ref REGISTRY: ExtensionRegistry = {
-        let mut registry = super::REGISTRY.to_owned();
+        let mut registry = qsystem::REGISTRY.to_owned();
         registry.register(tket2::extension::rotation::ROTATION_EXTENSION.to_owned()).unwrap();
         registry
     };
@@ -111,7 +111,7 @@ fn build_to_radians(b: &mut DFGBuilder<Hugr>, rotation: Wire) -> Result<Wire, Bu
     Ok(float)
 }
 
-/// Lower `Tk2Op` operations to `HSeriesOp` operations.
+/// Lower `Tk2Op` operations to `QSystemOp` operations.
 pub fn lower_tk2_op(hugr: &mut impl HugrMut) -> Result<Vec<hugr::Node>, LowerTk2Error> {
     let mut replaced_nodes = lower_direct(hugr)?;
     let mut hugr_map: HashMap<Tk2Op, Hugr> = HashMap::new();
@@ -136,10 +136,10 @@ fn lower_direct(hugr: &mut impl HugrMut) -> Result<Vec<Node>, LowerTk2Error> {
     Ok(hugr::algorithms::replace_many_ops(hugr, |op| {
         let op: Tk2Op = op.cast()?;
         Some(match op {
-            Tk2Op::TryQAlloc => HSeriesOp::TryQAlloc,
-            Tk2Op::QFree => HSeriesOp::QFree,
-            Tk2Op::Reset => HSeriesOp::Reset,
-            Tk2Op::MeasureFree => HSeriesOp::Measure,
+            Tk2Op::TryQAlloc => QSystemOp::TryQAlloc,
+            Tk2Op::QFree => QSystemOp::QFree,
+            Tk2Op::Reset => QSystemOp::Reset,
+            Tk2Op::MeasureFree => QSystemOp::Measure,
             _ => return None,
         })
     })?
@@ -171,15 +171,15 @@ pub fn check_lowered(hugr: &impl HugrView) -> Result<(), Vec<Node>> {
 }
 
 /// A `Hugr -> Hugr` pass that replaces [tket2::Tk2Op] nodes to
-/// equivalent graphs made of [HSeriesOp]s.
+/// equivalent graphs made of [QSystemOp]s.
 ///
 /// Invokes [lower_tk2_op]. If validation is enabled the resulting HUGR is
 /// checked with [check_lowered].
 #[derive(Default, Debug, Clone)]
-pub struct LowerTket2ToHSeriesPass(ValidationLevel);
+pub struct LowerTket2ToQSystemPass(ValidationLevel);
 
-impl LowerTket2ToHSeriesPass {
-    /// Run `LowerTket2ToHSeriesPass` on the given [HugrMut]. `registry` is used
+impl LowerTket2ToQSystemPass {
+    /// Run `LowerTket2ToQSystemPass` on the given [HugrMut]. `registry` is used
     /// for validation, if enabled.
     pub fn run(
         &self,
@@ -196,7 +196,7 @@ impl LowerTket2ToHSeriesPass {
         })
     }
 
-    /// Returns a new `LowerTket2ToHSeriesPass` with the given [ValidationLevel].
+    /// Returns a new `LowerTket2ToQSystemPass` with the given [ValidationLevel].
     pub fn with_validation_level(&self, level: ValidationLevel) -> Self {
         Self(level)
     }
@@ -245,35 +245,35 @@ mod test {
         let lowered = lower_direct(&mut h).unwrap();
         assert_eq!(lowered.len(), 5);
         let circ = Circuit::new(&h, h.root());
-        let ops: Vec<HSeriesOp> = circ
+        let ops: Vec<QSystemOp> = circ
             .commands()
             .filter_map(|com| com.optype().cast())
             .collect();
         assert_eq!(
             ops,
             vec![
-                HSeriesOp::TryQAlloc,
-                HSeriesOp::Measure,
-                HSeriesOp::TryQAlloc,
-                HSeriesOp::Reset,
-                HSeriesOp::QFree,
+                QSystemOp::TryQAlloc,
+                QSystemOp::Measure,
+                QSystemOp::TryQAlloc,
+                QSystemOp::Reset,
+                QSystemOp::QFree,
             ]
         );
         assert_eq!(check_lowered(&h), Ok(()));
     }
 
     #[rstest]
-    #[case(Tk2Op::H, Some(vec![HSeriesOp::PhasedX, HSeriesOp::Rz]))]
-    #[case(Tk2Op::X, Some(vec![HSeriesOp::PhasedX]))]
-    #[case(Tk2Op::Y, Some(vec![HSeriesOp::PhasedX]))]
-    #[case(Tk2Op::Z, Some(vec![HSeriesOp::Rz]))]
-    #[case(Tk2Op::S, Some(vec![HSeriesOp::Rz]))]
-    #[case(Tk2Op::Sdg, Some(vec![HSeriesOp::Rz]))]
-    #[case(Tk2Op::T, Some(vec![HSeriesOp::Rz]))]
-    #[case(Tk2Op::Tdg, Some(vec![HSeriesOp::Rz]))]
-    #[case(Tk2Op::Rx, Some(vec![HSeriesOp::PhasedX]))]
-    #[case(Tk2Op::Ry, Some(vec![HSeriesOp::PhasedX]))]
-    #[case(Tk2Op::Rz, Some(vec![HSeriesOp::Rz]))]
+    #[case(Tk2Op::H, Some(vec![QSystemOp::PhasedX, QSystemOp::Rz]))]
+    #[case(Tk2Op::X, Some(vec![QSystemOp::PhasedX]))]
+    #[case(Tk2Op::Y, Some(vec![QSystemOp::PhasedX]))]
+    #[case(Tk2Op::Z, Some(vec![QSystemOp::Rz]))]
+    #[case(Tk2Op::S, Some(vec![QSystemOp::Rz]))]
+    #[case(Tk2Op::Sdg, Some(vec![QSystemOp::Rz]))]
+    #[case(Tk2Op::T, Some(vec![QSystemOp::Rz]))]
+    #[case(Tk2Op::Tdg, Some(vec![QSystemOp::Rz]))]
+    #[case(Tk2Op::Rx, Some(vec![QSystemOp::PhasedX]))]
+    #[case(Tk2Op::Ry, Some(vec![QSystemOp::PhasedX]))]
+    #[case(Tk2Op::Rz, Some(vec![QSystemOp::Rz]))]
     // multi qubit ordering is not deterministic
     #[case(Tk2Op::CX, None)]
     #[case(Tk2Op::CY, None)]
@@ -283,17 +283,17 @@ mod test {
     // conditional doesn't fit in to commands
     #[case(Tk2Op::Measure, None)]
     #[case(Tk2Op::QAlloc, None)]
-    fn test_lower(#[case] t2op: Tk2Op, #[case] hseries_ops: Option<Vec<HSeriesOp>>) {
+    fn test_lower(#[case] t2op: Tk2Op, #[case] qsystem_ops: Option<Vec<QSystemOp>>) {
         // build dfg with just the op
 
         let h = op_to_hugr(t2op).unwrap();
         let circ = Circuit::new(&h, h.root());
-        let ops: Vec<HSeriesOp> = circ
+        let ops: Vec<QSystemOp> = circ
             .commands()
             .filter_map(|com| com.optype().cast())
             .collect();
-        if let Some(hseries_ops) = hseries_ops {
-            assert_eq!(ops, hseries_ops);
+        if let Some(qsystem_ops) = qsystem_ops {
+            assert_eq!(ops, qsystem_ops);
         }
 
         assert_eq!(check_lowered(&h), Ok(()));
diff --git a/tket2-hseries/src/lazify_measure.rs b/tket2-hseries/src/lazify_measure.rs
index d17049a8..66dfefb5 100644
--- a/tket2-hseries/src/lazify_measure.rs
+++ b/tket2-hseries/src/lazify_measure.rs
@@ -1,8 +1,8 @@
 //! Provides `LazifyMeasurePass` which replaces [Tket2Op::Measure] nodes with
-//! [HSeriesOp::Measure] nodes.
+//! [QSystemOp::Measure] nodes.
 //!
 //! [Tket2Op::Measure]: tket2::Tk2Op::Measure
-//! [HSeriesOp::Measure]: crate::extension::hseries::HSeriesOp::Measure
+//! [QSystemOp::Measure]: crate::extension::qsystem::QSystemOp::Measure
 use std::collections::{HashMap, HashSet};
 
 use derive_more::{Display, Error, From};
@@ -27,11 +27,11 @@ use lazy_static::lazy_static;
 
 use crate::extension::{
     futures::FutureOpBuilder,
-    hseries::{self, HSeriesOpBuilder},
+    qsystem::{self, QSystemOpBuilder},
 };
 
 /// A `Hugr -> Hugr` pass that replaces [tket2::Tk2Op::Measure] nodes with
-/// [hseries::HSeriesOp::Measure] nodes. To construct a `LazifyMeasurePass` use
+/// [qsystem::QSystemOp::Measure] nodes. To construct a `LazifyMeasurePass` use
 /// [Default::default].
 ///
 /// The `Hugr` must not contain any non-local edges. If validation is enabled,
@@ -114,7 +114,7 @@ lazy_static! {
         let [qb, lazy_r] = builder.add_lazy_measure(qb).unwrap();
         let [r] = builder.add_read(lazy_r, BOOL_T).unwrap();
         builder
-            .finish_hugr_with_outputs([qb, r], &hseries::REGISTRY)
+            .finish_hugr_with_outputs([qb, r], &qsystem::REGISTRY)
             .unwrap()
     };
 }
@@ -146,7 +146,7 @@ fn measure_replacement(num_dups: usize) -> Hugr {
     assert_eq!(num_out_types, rs.len());
     assert_eq!(num_out_types, num_dups + 1);
     builder
-        .finish_hugr_with_outputs(rs, &hseries::REGISTRY)
+        .finish_hugr_with_outputs(rs, &qsystem::REGISTRY)
         .unwrap()
 }
 
@@ -223,14 +223,14 @@ mod test {
 
     use crate::extension::{
         futures::{self, FutureOpDef},
-        hseries::HSeriesOp,
+        qsystem::QSystemOp,
     };
 
     use super::*;
 
     lazy_static! {
         pub static ref REGISTRY: ExtensionRegistry = ExtensionRegistry::try_new([
-            hseries::EXTENSION.to_owned(),
+            qsystem::EXTENSION.to_owned(),
             futures::EXTENSION.to_owned(),
             TKET2_EXTENSION.to_owned(),
             PRELUDE.to_owned(),
@@ -260,7 +260,7 @@ mod test {
             let ot = hugr.get_optype(n);
             if let Some(FutureOpDef::Read) = ot.cast() {
                 num_read += 1;
-            } else if let Some(HSeriesOp::LazyMeasure) = ot.cast() {
+            } else if let Some(QSystemOp::LazyMeasure) = ot.cast() {
                 num_lazy_measure += 1;
             } else {
                 assert_eq!(ot.cast::<Tk2Op>(), None)
diff --git a/tket2-hseries/src/lib.rs b/tket2-hseries/src/lib.rs
index 5557d335..2079204c 100644
--- a/tket2-hseries/src/lib.rs
+++ b/tket2-hseries/src/lib.rs
@@ -13,7 +13,7 @@ use tket2::Tk2Op;
 
 use extension::{
     futures::FutureOpDef,
-    hseries::{HSeriesOp, LowerTk2Error, LowerTket2ToHSeriesPass},
+    qsystem::{LowerTk2Error, LowerTket2ToQSystemPass, QSystemOp},
 };
 use lazify_measure::{LazifyMeasurePass, LazifyMeasurePassError};
 
@@ -23,44 +23,44 @@ pub mod extension;
 
 pub mod lazify_measure;
 
-/// Modify a [hugr::Hugr] into a form that is acceptable for ingress into an H-series.
+/// Modify a [hugr::Hugr] into a form that is acceptable for ingress into a Q-System.
 /// Returns an error if this cannot be done.
 ///
-/// To construct a `HSeriesPass` use [Default::default].
+/// To construct a `QSystemPass` use [Default::default].
 #[derive(Debug, Clone, Copy, Default)]
-pub struct HSeriesPass {
+pub struct QSystemPass {
     validation_level: ValidationLevel,
 }
 
 #[derive(Error, Debug, Display, From)]
 #[non_exhaustive]
-/// An error reported from [HSeriesPass].
-pub enum HSeriesPassError {
+/// An error reported from [QSystemPass].
+pub enum QSystemPassError {
     /// The [hugr::Hugr] was invalid either before or after a pass ran.
     ValidationError(ValidatePassError),
     /// An error from the component [LazifyMeasurePass].
     LazyMeasureError(LazifyMeasurePassError),
     /// An error from the component [force_order()] pass.
     ForceOrderError(HugrError),
-    /// An error from the component [LowerTket2ToHSeriesPass] pass.
+    /// An error from the component [LowerTket2ToQSystemPass] pass.
     LowerTk2Error(LowerTk2Error),
 }
 
-impl HSeriesPass {
-    /// Run `HSeriesPass` on the given [HugrMut]. `registry` is used for
+impl QSystemPass {
+    /// Run `QSystemPass` on the given [HugrMut]. `registry` is used for
     /// validation, if enabled.
     pub fn run(
         &self,
         hugr: &mut impl HugrMut,
         registry: &ExtensionRegistry,
-    ) -> Result<(), HSeriesPassError> {
+    ) -> Result<(), QSystemPassError> {
         self.lower_tk2().run(hugr, registry)?;
         self.lazify_measure().run(hugr, registry)?;
         self.validation_level
             .run_validated_pass(hugr, registry, |hugr, _| {
                 force_order(hugr, hugr.root(), |hugr, node| {
                     let optype = hugr.get_optype(node);
-                    if optype.cast::<Tk2Op>().is_some() || optype.cast::<HSeriesOp>().is_some() {
+                    if optype.cast::<Tk2Op>().is_some() || optype.cast::<QSystemOp>().is_some() {
                         // quantum ops are lifted as early as possible
                         -1
                     } else if let Some(FutureOpDef::Read) = hugr.get_optype(node).cast() {
@@ -70,20 +70,20 @@ impl HSeriesPass {
                         0
                     }
                 })?;
-                Ok::<_, HSeriesPassError>(())
+                Ok::<_, QSystemPassError>(())
             })?;
         Ok(())
     }
 
-    fn lower_tk2(&self) -> LowerTket2ToHSeriesPass {
-        LowerTket2ToHSeriesPass::default().with_validation_level(self.validation_level)
+    fn lower_tk2(&self) -> LowerTket2ToQSystemPass {
+        LowerTket2ToQSystemPass::default().with_validation_level(self.validation_level)
     }
 
     fn lazify_measure(&self) -> LazifyMeasurePass {
         LazifyMeasurePass::default().with_validation_level(self.validation_level)
     }
 
-    /// Returns a new `HSeriesPass` with the given [ValidationLevel].
+    /// Returns a new `QSystemPass` with the given [ValidationLevel].
     pub fn with_validation_level(mut self, level: ValidationLevel) -> Self {
         self.validation_level = level;
         self
@@ -105,12 +105,12 @@ mod test {
     use petgraph::visit::{Topo, Walker as _};
 
     use crate::{
-        extension::{futures::FutureOpDef, hseries::HSeriesOp},
-        HSeriesPass,
+        extension::{futures::FutureOpDef, qsystem::QSystemOp},
+        QSystemPass,
     };
 
     #[test]
-    fn hseries_pass() {
+    fn qsystem_pass() {
         let registry = &tket2::extension::REGISTRY;
         let (mut hugr, [call_node, h_node, f_node, rx_node]) = {
             let mut builder = DFGBuilder::new(Signature::new(QB_T, vec![BOOL_T, BOOL_T])).unwrap();
@@ -134,14 +134,14 @@ mod test {
 
             // with no dependencies, this Reset should be lifted to the start
             let [qb] = builder
-                .add_dataflow_op(HSeriesOp::Reset, [qb])
+                .add_dataflow_op(QSystemOp::Reset, [qb])
                 .unwrap()
                 .outputs_arr();
             let h_node = qb.node();
 
             // depending on the angle means this op can't be lifted above the angle ops
             let [qb] = builder
-                .add_dataflow_op(HSeriesOp::Rz, [qb, angle])
+                .add_dataflow_op(QSystemOp::Rz, [qb, angle])
                 .unwrap()
                 .outputs_arr();
             let rx_node = qb.node();
@@ -150,7 +150,7 @@ mod test {
             // Reads will be added.  The Lazy Measure will be lifted and the
             // reads will be sunk.
             let [measure_result] = builder
-                .add_dataflow_op(HSeriesOp::Measure, [qb])
+                .add_dataflow_op(QSystemOp::Measure, [qb])
                 .unwrap()
                 .outputs_arr();
 
@@ -160,7 +160,7 @@ mod test {
             (hugr, [call_node, h_node, f_node, rx_node])
         };
 
-        HSeriesPass::default().run(&mut hugr, registry).unwrap();
+        QSystemPass::default().run(&mut hugr, registry).unwrap();
 
         let topo_sorted = Topo::new(&hugr.as_petgraph())
             .iter(&hugr.as_petgraph())
diff --git a/tket2-py/tket2/circuit/build.py b/tket2-py/tket2/circuit/build.py
index c0b5554f..3c568a04 100644
--- a/tket2-py/tket2/circuit/build.py
+++ b/tket2-py/tket2/circuit/build.py
@@ -52,7 +52,7 @@ def finish_package(
         extensions = [
             ext.rotation(),
             ext.futures(),
-            ext.hseries(),
+            ext.qsystem(),
             ext.quantum(),
             ext.result(),
             *(other_extensions or []),
diff --git a/tket2-py/tket2/extensions/__init__.py b/tket2-py/tket2/extensions/__init__.py
index c90c382d..58354f40 100644
--- a/tket2-py/tket2/extensions/__init__.py
+++ b/tket2-py/tket2/extensions/__init__.py
@@ -1,4 +1,4 @@
-from tket2_exts import rotation, futures, hseries, quantum, result
+from tket2_exts import rotation, futures, qsystem, quantum, result
 
 
-__all__ = ["rotation", "futures", "hseries", "quantum", "result"]
+__all__ = ["rotation", "futures", "qsystem", "quantum", "result"]