diff --git a/.github/workflows/build_and_test.yml b/.github/workflows/build_and_test.yml
index 249732b..641603f 100644
--- a/.github/workflows/build_and_test.yml
+++ b/.github/workflows/build_and_test.yml
@@ -28,6 +28,7 @@ jobs:
     - uses: actions/checkout@v4
       with:
         fetch-depth: '0'
+        submodules: true
     - run: git fetch --depth=1 origin +refs/tags/*:refs/tags/* +refs/heads/*:refs/remotes/origin/*
     - name: Set up Python 3.10
       if: github.event_name == 'push' || github.event_name == 'schedule'
@@ -68,15 +69,20 @@ jobs:
       with:
         name: artefact-${{ matrix.os }}
         path: wheelhouse/
+    - name: install poetry
+      run: pip install poetry
     - name: Install docs dependencies
       if:  (matrix.os == 'ubuntu-22.04') && (github.event_name == 'pull_request' || github.event_name == 'schedule' )
       run: |
-        pip install -r .github/workflows/docs/requirements.txt
+        cd docs
+        bash ./install.sh
+        for w in `find wheelhouse/ -type f -name "*.whl"` ; do poetry install $w ; done
     - name: Build docs
       if:  (matrix.os == 'ubuntu-22.04') && (github.event_name == 'pull_request' || github.event_name == 'schedule' )
       timeout-minutes: 20
       run: |
-        ./.github/workflows/docs/check-build-docs
+        cd docs
+        poetry run bash ./build-docs.sh
 
 
   publish_to_pypi:
@@ -113,24 +119,27 @@ jobs:
     - uses: actions/checkout@v4
       with:
         fetch-depth: '0'
-    - name: Set up Python 3.10
+        submodules: true
+    - name: Set up Python 3.11
       uses: actions/setup-python@v5
       with:
-        python-version: '3.10'
+        python-version: '3.11'
     - name: Download all wheels
       uses: actions/download-artifact@v4
       with:
         path: wheelhouse
     - name: Install pip, wheel
       run: pip install -U pip wheel
+    - name: Install poetry
+      run: pip install poetry
     - name: Install extension
-      run: for w in `find wheelhouse/ -type f -name "*.whl"` ; do pip install $w ; done
+      run: for w in `find wheelhouse/ -type f -name "*.whl"` ; do poetry install $w ; done
     - name: Install docs dependencies
       run: |
-        pip install -r .github/workflows/docs/requirements.txt
+        cd docs
+        bash ./install.sh
     - name: Build docs
       timeout-minutes: 20
       run: |
-        cd .github/workflows/docs
-        mkdir extensions
-        ./build-docs -d ${GITHUB_WORKSPACE}/.github/workflows/docs/extensions/api
+        cd docs
+        poetry run bash ./build-docs.sh
diff --git a/.github/workflows/docs.yml b/.github/workflows/docs.yml
index 4ace326..813487a 100644
--- a/.github/workflows/docs.yml
+++ b/.github/workflows/docs.yml
@@ -1,4 +1,4 @@
-name: Pytket ProjectQ Docs
+name: Build docs
 
 on:
   push:
@@ -7,30 +7,27 @@ on:
   schedule:
     # 04:00 every Tuesday morning
     - cron: '0 4 * * 2'
+
 jobs:
   docs:
     name: build docs
     runs-on: ubuntu-22.04
     steps:
     - uses: actions/checkout@v4
-    - name: Set up Python 3.10
+      with: 
+        submodules: true
+    - name: Set up Python 3.11
       uses: actions/setup-python@v5
       with:
-        python-version: '3.10'
-    - name: Upgrade pip and install wheel
-      run: pip install --upgrade pip wheel
-    - name: Install pytket projectq
-      run: pip install .
+        python-version: '3.11'
+    - name: install poetry
+      run: pip install poetry
     - name: Install docs dependencies
-      run: |
-        pip install -r .github/workflows/docs/requirements.txt
+      run: cd docs && bash install.sh 
+    - name: Install pytket projectq
+      run: cd docs && poetry run pip install ../.
     - name: Test building docs
-      timeout-minutes: 20
+      timeout-minutes: 10
       run: |
-        cd .github/workflows/docs
-        mkdir extensions
-        ./build-docs -d ${GITHUB_WORKSPACE}/.github/workflows/docs/extensions
-    - uses: actions/upload-artifact@v4
-      with:
-        name: pytket-extension-docs
-        path: .github/workflows/docs/extensions/
+        cd docs
+        poetry run bash build-docs.sh
\ No newline at end of file
diff --git a/.github/workflows/docs/Quantinuum_logo_black.png b/.github/workflows/docs/Quantinuum_logo_black.png
deleted file mode 100644
index 5569581..0000000
Binary files a/.github/workflows/docs/Quantinuum_logo_black.png and /dev/null differ
diff --git a/.github/workflows/docs/Quantinuum_logo_white.png b/.github/workflows/docs/Quantinuum_logo_white.png
deleted file mode 100644
index e896db9..0000000
Binary files a/.github/workflows/docs/Quantinuum_logo_white.png and /dev/null differ
diff --git a/.github/workflows/docs/build-docs b/.github/workflows/docs/build-docs
deleted file mode 100755
index 1bae76c..0000000
--- a/.github/workflows/docs/build-docs
+++ /dev/null
@@ -1,112 +0,0 @@
-#!/usr/bin/env python
-
-import argparse
-import datetime
-from importlib import import_module
-from pathlib import Path
-import shutil
-import subprocess
-import sys
-
-DOCS_DIR = Path(sys.argv[0]).absolute().parent
-MODULES_DIR = DOCS_DIR.parent.parent.parent
-TKET_EXAMPLES_LINK = "https://tket.quantinuum.com/examples/"
-TKET_MANUAL_LINK = "https://tket.quantinuum.com/user-manual/"
-TKET_WEBSITE_LINK = "https://tket.quantinuum.com/"
-PYTKET_DOCS_LINK = "https://tket.quantinuum.com/api-docs/"
-PYTKET_EX_DOCS_LINK = "https://tket.quantinuum.com/api-docs/extensions.html"
-PYTKET_PROJECTQ_PYPI_LINK = "https://pypi.org/project/pytket-projectq/"
-PYTKET_PROJECTQ_GITHUB = "https://github.com/CQCL/pytket-projectq"
-MODULE = "projectq"
-
-def get_module_version():
-    m = import_module(f"pytket.extensions.{MODULE}")
-    return m._metadata.__extension_version__.split(".")
-
-
-def remove_dir(dirpath):
-    if dirpath.exists() and dirpath.is_dir():
-        shutil.rmtree(dirpath)
-
-
-def fix_links(filepath):
-    with open(filepath, "r", encoding="utf8") as f:
-        content = f.read()
-    content = content.replace("pytket._tket", "pytket")
-    with open(filepath, "w", encoding="utf8") as f:
-        f.write(content)
-
-
-def build_module_docs():
-    v = get_module_version()
-    mod_docs = MODULES_DIR / "docs"
-    mod_build = mod_docs / "build"
-    conf_copy = mod_docs / "conf.py"
-    logo_copy_black = mod_docs / "Quantinuum_logo_black.png"
-    logo_copy_white = mod_docs / "Quantinuum_logo_white.png"
-    shutil.copy(DOCS_DIR / "conf.py", conf_copy)
-    shutil.copy(DOCS_DIR / "Quantinuum_logo_black.png", logo_copy_black)
-    shutil.copy(DOCS_DIR / "Quantinuum_logo_white.png", logo_copy_white)
-    remove_dir(mod_build)
-    index_rst = mod_docs / "index.rst"
-    with open(mod_docs / "intro.txt", "r") as f:
-        content = f.readlines()
-        content.append(
-            "\n.. toctree::\n\t:caption: pytket documentation:\n\t:maxdepth: 1\n\n"
-        )
-        content.append(f"\tpytket API docs <{PYTKET_DOCS_LINK}>\n")
-        content.append(f"\tpytket extensions <{PYTKET_EX_DOCS_LINK}>\n")
-        content.append(f"\tManual <{TKET_MANUAL_LINK}>\n")
-        content.append(f"\tExample notebooks <{TKET_EXAMPLES_LINK}>\n")
-        content.append(f"\tTKET website <{TKET_WEBSITE_LINK}>\n")
-        content.append(
-            "\n.. toctree::\n\t:caption: Links:\n\t:maxdepth: 1\n\n"
-        )
-        content.append(f"\tbug tracker <{PYTKET_PROJECTQ_GITHUB}/issues>\n")
-        content.append(f"\tGitHub <{PYTKET_PROJECTQ_GITHUB}>\n")
-        content.append(f"\tPyPi <{PYTKET_PROJECTQ_PYPI_LINK}>\n")        
-
-    with open(index_rst, "w") as f:
-        f.writelines(content)
-    subprocess.run(
-        [
-            "sphinx-build",
-            "-b",
-            "html",
-            "-D",
-            f"project=pytket-{MODULE}",
-            "-D",
-            f"version={'.'.join(v[:2])}",
-            "-D",
-            f"release={'.'.join(v)}",
-            ".",
-            "build",
-        ],
-        cwd=mod_docs,
-    )
-    for htmlfile in mod_build.rglob("*.html"):
-        fix_links(htmlfile)
-    fix_links(mod_build / "searchindex.js")
-    conf_copy.unlink()
-    logo_copy_black.unlink()
-    logo_copy_white.unlink()
-    index_rst.unlink()
-
-
-if __name__ == "__main__":
-    parser = argparse.ArgumentParser(
-        description="Build HTML documentation for pytket-projectq."
-    )
-    parser.add_argument("-d", "--dest", help="copy artifacts into destination folder")
-    args = parser.parse_args()
-
-    print("Building docs for modules:", MODULE)
-    build_module_docs()
-
-    if args.dest is not None:
-        dest = Path(args.dest)
-        shutil.copytree(
-            MODULES_DIR / "docs" / "build",
-            dest,
-            dirs_exist_ok=True,
-            )
diff --git a/.github/workflows/docs/check-build-docs b/.github/workflows/docs/check-build-docs
deleted file mode 100755
index 6812eb7..0000000
--- a/.github/workflows/docs/check-build-docs
+++ /dev/null
@@ -1,10 +0,0 @@
-#!/bin/bash
-
-./.github/workflows/docs/build-docs 1>out.txt 2>err.txt
-cat out.txt err.txt
-ERRS=`cat err.txt`
-if [ ! -z $ERRS ]
-then
-    echo "Docs build failed."
-    exit 1
-fi
diff --git a/.github/workflows/docs/conf.py b/.github/workflows/docs/conf.py
deleted file mode 100644
index f027627..0000000
--- a/.github/workflows/docs/conf.py
+++ /dev/null
@@ -1,145 +0,0 @@
-# -*- coding: utf-8 -*-
-
-# Configuration file for the Sphinx documentation builder.
-# See https://www.sphinx-doc.org/en/master/usage/configuration.html
-
-author = "Quantinuum"
-
-extensions = [
-    "sphinx.ext.autodoc",
-    "sphinx.ext.autosummary",
-    "sphinx.ext.intersphinx",
-    "sphinx.ext.mathjax",
-    "sphinx_copybutton",
-]
-
-pygments_style = "borland"
-
-html_theme = "sphinx_book_theme"
-
-html_theme_options = {
-    "repository_url": "https://github.com/CQCL/pytket-projectq",
-    "use_repository_button": True,
-    "use_issues_button": True,
-    "logo": {
-        "image_light": "Quantinuum_logo_black.png",
-        "image_dark": "Quantinuum_logo_white.png",
-    },
-}
-
-html_static_path = ["_static"]
-
-html_css_files = ["custom.css"]
-
-# -- Extension configuration -------------------------------------------------
-
-pytketdoc_base = "https://tket.quantinuum.com/api-docs/"
-
-intersphinx_mapping = {
-    "https://docs.python.org/3/": None,
-    pytketdoc_base: None,
-    "https://qiskit.org/documentation/": None,
-    "http://docs.qulacs.org/en/latest/": None,
-}
-
-autodoc_member_order = "groupwise"
-
-# The following code is for resolving broken hyperlinks in the doc.
-
-import re
-from typing import Any, Dict, List, Optional
-from urllib.parse import urljoin
-
-from docutils import nodes
-from docutils.nodes import Element, TextElement
-from sphinx.application import Sphinx
-from sphinx.environment import BuildEnvironment
-
-# Mappings for broken hyperlinks that intersphinx cannot resolve
-external_url_mapping = {
-    "BasePass": urljoin(pytketdoc_base, "passes.html#pytket.passes.BasePass"),
-    "Predicate": urljoin(pytketdoc_base, "predicates.html#pytket.predicates.Predicate"),
-    "ResultHandle": urljoin(
-        pytketdoc_base,
-        "backends.html#pytket.backends.resulthandle.ResultHandle",
-    ),
-    "BackendResult": urljoin(
-        pytketdoc_base,
-        "backends.html#pytket.backends.backendresult.BackendResult",
-    ),
-    "Circuit": urljoin(pytketdoc_base, "circuit_class.html#pytket.circuit.Circuit"),
-    "BasisOrder": urljoin(pytketdoc_base, "circuit.html#pytket.circuit.BasisOrder"),
-    "QubitPauliOperator": urljoin(
-        pytketdoc_base, "utils.html#pytket.utils.QubitPauliOperator"
-    ),
-    "QubitPauliString": urljoin(
-        pytketdoc_base, "pauli.html#pytket.pauli.QubitPauliString"
-    ),
-}
-
-# Correct mappings for intersphinx to resolve
-custom_internal_mapping = {
-    "pytket.utils.outcomearray.OutcomeArray": "pytket.utils.OutcomeArray",
-    "pytket.utils.operators.QubitPauliOperator": "pytket.utils.QubitPauliOperator",
-    "pytket.backends.backend.Backend": "pytket.backends.Backend",
-    "qiskit.dagcircuit.dagcircuit.DAGCircuit": "qiskit.dagcircuit.DAGCircuit",
-    "qiskit.providers.basebackend.BaseBackend": "qiskit.providers.BaseBackend",
-    "qiskit.qobj.qasm_qobj.QasmQobj": "qiskit.qobj.QasmQobj",
-    "qiskit.result.result.Result": "qiskit.result.Result",
-}
-
-
-def add_reference(
-    app: Sphinx, env: BuildEnvironment, node: Element, contnode: TextElement
-) -> Optional[nodes.reference]:
-    # Fix references in docstrings that are inherited from the base pytket.backends.Backend class.
-    mapping = app.config.external_url_mapping
-    if node.astext() in mapping:
-        newnode = nodes.reference(
-            "",
-            "",
-            internal=False,
-            refuri=mapping[node.astext()],
-            reftitle=node.get("reftitle", node.astext()),
-        )
-        newnode.append(contnode)
-        return newnode
-    return None
-
-
-def correct_signature(
-    app: Sphinx,
-    what: str,
-    name: str,
-    obj: Any,
-    options: Dict,
-    signature: str,
-    return_annotation: str,
-) -> (str, str):
-
-    new_signature = signature
-    new_return_annotation = return_annotation
-    for k, v in app.config.custom_internal_mapping.items():
-        if signature is not None:
-            new_signature = new_signature.replace(k, v)
-        if return_annotation is not None:
-            new_return_annotation = new_return_annotation.replace(k, v)
-    # e.g. Replace <CXConfigType.Snake: 0> by CXConfigType.Snake to avoid silent failure in later stages.
-    if new_signature is not None:
-        enums_signature = re.findall(r"<.+?\: \d+>", new_signature)
-        for e in enums_signature:
-            new_signature = new_signature.replace(e, e[1 : e.find(":")])
-
-    if new_return_annotation is not None:
-        enums_return = re.findall(r"<.+?\: \d+>", new_return_annotation)
-        for e in enums_return:
-            new_return_annotation = new_return_annotation.replace(e, e[1 : e.find(":")])
-
-    return new_signature, new_return_annotation
-
-
-def setup(app):
-    app.add_config_value("custom_internal_mapping", {}, "env")
-    app.add_config_value("external_url_mapping", {}, "env")
-    app.connect("missing-reference", add_reference)
-    app.connect("autodoc-process-signature", correct_signature)
diff --git a/.github/workflows/docs/intro.txt b/.github/workflows/docs/intro.txt
deleted file mode 100644
index ce587b0..0000000
--- a/.github/workflows/docs/intro.txt
+++ /dev/null
@@ -1,10 +0,0 @@
-pytket-extensions
-=================
-
-These extensions enable ``pytket` to be used in conjunction with other
-platforms. Each extension adds either new methods to the ``pytket`` package to
-convert between circuit representations, or new backends to which ``pytket``
-circuits can be submitted.
-
-.. _pytket: https://tket.quantinuum.com/api-docs/
-.. _Quantinuum: https://www.quantinuum.com/
diff --git a/.github/workflows/docs/requirements.txt b/.github/workflows/docs/requirements.txt
deleted file mode 100644
index e893f3c..0000000
--- a/.github/workflows/docs/requirements.txt
+++ /dev/null
@@ -1,3 +0,0 @@
-sphinx ~= 6.2
-sphinx_book_theme >= 1.0.1, <2.0
-sphinx-copybutton
diff --git a/.github/workflows/docs/templates/searchbox.html b/.github/workflows/docs/templates/searchbox.html
deleted file mode 100644
index e69de29..0000000
diff --git a/.gitignore b/.gitignore
index 2b80d27..8bc0952 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,3 +11,6 @@ obj
 docs/extensions
 .ipynb_checkpoints
 pytket/extensions/projectq/_metadata.py
+.DS_Store
+docs/pyproject.toml
+docs/poetry.lock
diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..fdc8b03
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,4 @@
+[submodule "docs/pytket-docs-theming"]
+	path = docs/pytket-docs-theming
+	url = https://github.com/CQCL/pytket-docs-theming.git
+	branch = main
diff --git a/docs/README.md b/docs/README.md
new file mode 100644
index 0000000..6e20b65
--- /dev/null
+++ b/docs/README.md
@@ -0,0 +1,5 @@
+# Building the docs
+
+The docs are built by using the [pytket-docs-theming](https://github.com/CQCL/pytket-docs-theming/) repository as a git submodule. If there are issues with the docs build, feel free to open an issue or pull request there.
+
+For instructions on how to build the docs, take a look at the [extensions README](https://github.com/CQCL/pytket-docs-theming/blob/main/extensions/README.md).
diff --git a/docs/_static/custom.css b/docs/_static/custom.css
deleted file mode 100644
index 9c8a6ed..0000000
--- a/docs/_static/custom.css
+++ /dev/null
@@ -1,35 +0,0 @@
-.wy-side-nav-search,
-.wy-nav-top {
-    background: #5A46BE;
-}
-
-.wy-grid-for-nav,
-.wy-body-for-nav,
-.wy-nav-side,
-.wy-side-scroll,
-.wy-menu,
-.wy-menu-vertical {
-    background-color: #FFFFFF;
-}
-
-.wy-menu-vertical a:hover {
-    background-color: #d9d9d9;
-}
-
-.btn-link:visited,
-.btn-link,
-a:visited,
-.a.reference.external,
-.a.reference.internal,
-.wy-menu-vertical a,
-.wy-menu-vertical li,
-.wy-menu-vertical ul,
-.span.pre,
-.sig-param,
-html[data-theme=light] {
-    --pst-color-inline-code: rgb(199, 37, 78) !important;
-}
-
-.sig-name {
-    font-size: 1.25rem;
-}
\ No newline at end of file
diff --git a/docs/build-docs.sh b/docs/build-docs.sh
new file mode 100644
index 0000000..211c70a
--- /dev/null
+++ b/docs/build-docs.sh
@@ -0,0 +1,21 @@
+#!/bin/bash
+rm -rf build/
+
+# Move theming elements into the docs folder
+cp -R pytket-docs-theming/_static .
+cp -R pytket-docs-theming/quantinuum-sphinx .
+cp pytket-docs-theming/conf.py .
+
+# Get the name of the project
+EXTENSION_NAME="$(basename "$(dirname `pwd`)")"
+
+# Correct github link in navbar
+sed -i '' 's#CQCL/tket#CQCL/'$EXTENSION_NAME'#' _static/nav-config.js
+
+# Build the docs. Ensure we have the correct project title.
+sphinx-build -b html -D html_title="$EXTENSION_NAME" . build 
+
+# Remove copied files. This ensures reusability.
+rm -r _static 
+rm -r quantinuum-sphinx
+rm conf.py
\ No newline at end of file
diff --git a/docs/intro.txt b/docs/index.rst
similarity index 77%
rename from docs/intro.txt
rename to docs/index.rst
index ec97e03..f0c6809 100644
--- a/docs/intro.txt
+++ b/docs/index.rst
@@ -18,3 +18,9 @@ and Windows. To install, run:
 .. toctree::
     api.rst
     changelog.rst
+
+.. toctree::
+   :caption: Useful links
+
+   Issue tracker <https://github.com/CQCL/pytket-projectq/issues>
+   PyPi <https://pypi.org/project/pytket-projectq/>
\ No newline at end of file
diff --git a/docs/install.sh b/docs/install.sh
new file mode 100644
index 0000000..3ca1079
--- /dev/null
+++ b/docs/install.sh
@@ -0,0 +1,9 @@
+
+# Copy over poetry dependencies from theming repository
+cp pytket-docs-theming/extensions/pyproject.toml .
+cp pytket-docs-theming/extensions/poetry.lock .
+
+# Install the docs dependencies. Creates a .venv directory in docs
+poetry install
+
+# NOTE: Editable wheel should be installed separately.
\ No newline at end of file
diff --git a/docs/pytket-docs-theming b/docs/pytket-docs-theming
new file mode 160000
index 0000000..cfbe34c
--- /dev/null
+++ b/docs/pytket-docs-theming
@@ -0,0 +1 @@
+Subproject commit cfbe34c48f88c56085b8ef65f640d0108b8a9fa6
diff --git a/pytket/extensions/projectq/backends/projectq_backend.py b/pytket/extensions/projectq/backends/projectq_backend.py
index 2c049dd..f5b8308 100644
--- a/pytket/extensions/projectq/backends/projectq_backend.py
+++ b/pytket/extensions/projectq/backends/projectq_backend.py
@@ -286,7 +286,7 @@ def get_operator_expectation_value(
         """
         ham = projectq.ops.QubitOperator()
         for term, coeff in operator._dict.items():
-            if type(coeff) is complex and abs(coeff.imag) > 1e-12:  # type: ignore
+            if type(coeff) is complex and abs(coeff.imag) > 1e-12:
                 raise ValueError(
                     "Operator is not Hermitian and cannot be converted to "
                     "`projectq.ops.QubitOperator`."