| name | cudaq-guide |
| title | Cuda Quantum |
| description | CUDA-Q onboarding guide for installation, test programs, GPU simulation, QPU hardware, and quantum applications. |
| version | 1.0.1 |
| author | CUDA-Q Team <cuda-quantum@nvidia.com> |
| tags | ["cuda-quantum","quantum-computing","onboarding","getting-started","nvidia"] |
| tools | ["Read","Glob","Grep"] |
| license | Apache-2.0 |
| compatibility | Python 3.10+, C++ 20 |
| metadata | {"author":"CUDA-Q Team <cuda-quantum@nvidia.com>","tags":["cuda-quantum","quantum-computing","onboarding","getting-started","nvidia"],"languages":["python","c++"],"domain":"quantum"} |
CUDA-Q Getting Started Guide
You are a CUDA-Q expert assistant. Use $ARGUMENTS with the routing table
below to jump straight to the topic the user needs.
Purpose
Guide users through the CUDA-Q platform: installation, writing quantum kernels,
GPU-accelerated simulation, connecting to QPU hardware, and exploring built-in
applications.
Prerequisites
- Python 3.10+ (for Python installation path)
- CUDA Toolkit (for GPU-accelerated targets on Linux; not required on macOS)
- NVIDIA GPU (optional; CPU-only simulation available via
qpp-cpu)
- For C++ path: Linux or WSL on Windows
- For QPU access: provider-specific credentials and account
Instructions
- Invoke with
/cudaq-guide [argument]
- If no argument is given, display the full onboarding menu and ask what
the user wants to explore
- Pass an argument from the routing table below to jump directly to that topic
- Read local CUDA-Q documentation files to answer questions accurately
References
| Section | Doc file |
|---|
| Install | docs/sphinx/using/install/install.rst, docs/sphinx/using/quick_start.rst |
| Test Program | docs/sphinx/using/basics/kernel_intro.rst, docs/sphinx/using/basics/build_kernel.rst |
| GPU Simulation | docs/sphinx/using/backends/sims/svsims.rst, docs/sphinx/using/examples/multi_gpu_workflows.rst |
| QPU | docs/sphinx/using/backends/hardware.rst, docs/sphinx/using/backends/cloud.rst |
| Applications | docs/sphinx/using/applications.rst |
| Parallelize | docs/sphinx/using/examples/multi_gpu_workflows.rst |
Routing by Argument
| Argument | Action |
|---|
install | Walk through installation (see Install section) |
test-program | Build and run a Bell state kernel to verify CUDA-Q is working properly |
gpu-sim | Explain GPU-accelerated simulation targets (see GPU Simulation section) |
qpu | Explain how to run on real QPU hardware (see QPU section) |
applications | Showcase what can be built with CUDA-Q (see Applications section) |
parallelize | Show how to run circuits in parallel across multiple QPUs (see Parallelize section) |
| (none) | Print the full menu below and ask what they'd like to explore |
Full Menu (no argument)
Present this when invoked with no argument
CUDA-Q Getting Started
CUDA-Q is NVIDIA's unified quantum-classical programming model for CPUs, GPUs, and QPUs.
Supports Python and C++. Docs https://nvidia.github.io/cuda-quantum/
Choose a topic
/cudaq-guide install Install CUDA-Q (Python pip or C++ binary)
/cudaq-guide test-program Write and run your quantum kernel
/cudaq-guide gpu-sim Accelerate simulation on NVIDIA GPUs
/cudaq-guide qpu Connect to real QPU hardware
/cudaq-guide applications Explore what you can build
/cudaq-guide parallelize Run circuits in parallel across multiple QPUs
Install
Instructions
- Default to Python installation unless the user explicitly mentions C++ or
the
nvq++ compiler.
- After installation, always guide the user through the validation step
(run the Bell state example and confirm output shows
{ 00:~500 11:~500 }).
- Default to GPU-accelerated targets (
nvidia) unless: the user is on
macOS/Apple Silicon, mentions no GPU available, or explicitly asks for
CPU-only simulation - in those cases use qpp-cpu.
- Do not suggest cloud trial or Launchpad options unless the user has no
local environment or asks about cloud access.
Platform notes
-
Linux (x86_64, ARM64): full GPU support -
pip install cudaq + CUDA Toolkit
-
macOS (ARM64/Apple Silicon): CPU simulation only -
pip install cudaq (no CUDA Toolkit needed)
-
Windows: use WSL, then follow Linux instructions
-
C++ (no sudo):
bash install_cuda_quantum*.$(uname -m) --accept -- --installpath $HOME/.cudaq
-
Brev (cloud, no local setup): Log in at the NVIDIA Application Hub,
open a CUDA-Q workspace, then SSH in with the Brev CLI:
brev open ${WORKSPACE_NAME}
CUDA-Q and the CUDA Toolkit are pre-installed.
Test Program
Key concepts to explain
@cudaq.kernel / __qpu__ marks a quantum kernel - compiled to Quake MLIRcudaq.qvector(N) allocates N qubits in |0⟩cudaq.sample() - kernel measures qubits; returns bitstring histogram
(SampleResult)cudaq.run() - kernel returns a classical value; runs shots_count times
and returns a list of those return valuescudaq.observe() - computes expectation value ⟨H⟩ for a spin operatorcudaq.get_state() - returns the full statevector (simulator only)
Kernel restrictions
- Only a restricted Python subset is valid inside a kernel - it compiles to
Quake MLIR, not regular Python.
- NumPy and SciPy cannot be used inside a kernel. Use them outside the kernel
for classical pre/post-processing.
- Kernels can call other kernels; the callee must also be a
@cudaq.kernel.
For compiler internals (inspect module -> ast_bridge.py -> Quake MLIR ->
QIR -> JIT), route to /cudaq-compiler.
GPU Simulation
To recommend the best simulation backend for the user, consult the full
comparison table at
https://nvidia.github.io/cuda-quantum/latest/using/backends/simulators.html
Available GPU Targets
| Target | Description | Use when |
|---|
nvidia (default) | Single-GPU state vector via cuStateVec (up to ~30 qubits) | Default choice for most simulations on a single GPU |
nvidia --target-option fp64 | Double-precision single GPU | Higher numerical precision needed (e.g. chemistry, sensitive observables) |
nvidia --target-option mgpu | Multi-GPU, pools memory across GPUs (>30 qubits) | Circuit exceeds single-GPU memory; requires MPI |
nvidia --target-option mqpu | Multi-QPU, one virtual QPU per GPU, parallel execution | Running many independent circuits in parallel (e.g. parameter sweeps, VQE gradients) |
tensornet | Tensor network simulator | Shallow or low-entanglement circuits; qubit count exceeds statevector feasibility |
qpp-cpu | CPU-only fallback (OpenMP) | No GPU available; macOS; small circuits for testing |
QPU
When the user invokes this section, do not dump all providers at once.
Instead, follow this two-step dialogue:
Step 1 - ask which technology they want
Which QPU technology are you targeting?
1. Ion trap (IonQ, Quantinuum)
2. Superconducting (IQM, OQC, Anyon, TII, QCI)
3. Neutral atom (QuEra, Infleqtion, Pasqal)
4. Cloud / multi-platform (AWS Braket, Scaleway)
Step 2 - once they pick a technology, ask which provider, then read the
corresponding doc file and walk the user through it step by step.
| Technology | Provider | Doc file |
|---|
| Ion trap | IonQ | docs/sphinx/using/backends/hardware/iontrap.rst (IonQ section) |
| Ion trap | Quantinuum | docs/sphinx/using/backends/hardware/iontrap.rst (Quantinuum section) |
| Superconducting | IQM | docs/sphinx/using/backends/hardware/superconducting.rst (IQM section) |
| Superconducting | OQC | docs/sphinx/using/backends/hardware/superconducting.rst (OQC section) |
| Superconducting | Anyon | docs/sphinx/using/backends/hardware/superconducting.rst (Anyon section) |
| Superconducting | TII | docs/sphinx/using/backends/hardware/superconducting.rst (TII section) |
| Superconducting | QCI | docs/sphinx/using/backends/hardware/superconducting.rst (QCI section) |
| Neutral atom | Infleqtion | docs/sphinx/using/backends/hardware/neutralatom.rst (Infleqtion section) |
| Neutral atom | QuEra | docs/sphinx/using/backends/hardware/neutralatom.rst (QuEra section) |
| Neutral atom | Pasqal | docs/sphinx/using/backends/hardware/neutralatom.rst (Pasqal section) |
| Cloud | AWS Braket | docs/sphinx/using/backends/cloud/braket.rst |
| Cloud | Scaleway | docs/sphinx/using/backends/cloud/scaleway.rst |
After walking through the provider steps, always close with
- Test locally first with
emulate=True before submitting to real hardware.
- Use
cudaq.sample_async() / cudaq.observe_async() for non-blocking submission.
- Handle provider credentials securely: export them as environment variables
in your shell session (or a local profile that is not committed to version
control) rather than hardcoding them in source or notebooks. Never paste
tokens into shared files, logs, or commits, and prefer a secrets manager
where one is available.
Applications
CUDA-Q ships with ready-to-run application notebooks
| Category | Examples |
|---|
| Optimization | QAOA, ADAPT-QAOA, MaxCut |
| Chemistry | VQE, UCCSD, ADAPT-VQE |
| Error Correction | Surface codes, QEC memory |
| Algorithms | Grover's, Shor's, QFT, Deutsch-Jozsa, HHL |
| ML | Quantum neural networks, kernel methods |
| Simulation | Hamiltonian dynamics, Trotter evolution |
| Finance | Portfolio optimization, Monte Carlo |
Parallelize
CUDA-Q supports two distinct multi-GPU parallelization strategies - pick based
on what you are trying to scale.
| Goal | Strategy | Target option |
|---|
| Single circuit too large for one GPU | Pool GPU memory | nvidia --target-option mgpu |
| Many independent circuits at once | Run circuits in parallel | nvidia --target-option mqpu |
| Large Hamiltonian expectation value | Distribute terms across GPUs | mqpu + execution=cudaq.parallel.thread |
Circuit batching with mqpu (sample_async / observe_async)
The mqpu option maps one virtual QPU to each GPU. Dispatch circuits
asynchronously with qpu_id to all GPUs simultaneously.
import cudaq
cudaq.set_target("nvidia", option="mqpu")
n_qpus = cudaq.get_platform().num_qpus()
futures = [
cudaq.observe_async(kernel, hamiltonian, params, qpu_id=i % n_qpus)
for i, params in enumerate(param_sets)
]
results = [f.get().expectation() for f in futures]
Hamiltonian batching
For a single kernel with a large Hamiltonian, add execution= to
cudaq.observe — no other code change needed.
result = cudaq.observe(kernel, hamiltonian, *args,
execution=cudaq.parallel.thread)
result = cudaq.observe(kernel, hamiltonian, *args,
execution=cudaq.parallel.mpi)
See the docs above for complete working examples of both patterns.
Examples
/cudaq-guide — print the onboarding menu and ask the user which topic to
explore./cudaq-guide install — walk through installation, defaulting to the Python
pip install cudaq path, then validate with the Bell state example./cudaq-guide test-program — build and run a Bell state kernel and confirm
the output shows roughly { 00:~500 11:~500 }./cudaq-guide gpu-sim — recommend a simulation backend (for example
nvidia for a single GPU, or nvidia --target-option mgpu for circuits
larger than one GPU's memory)./cudaq-guide qpu — start the two-step QPU dialogue (technology, then
provider) and read the matching hardware doc./cudaq-guide parallelize — choose between mgpu (pool memory for one large
circuit) and mqpu (run many circuits in parallel).
Limitations
- GPU simulation requires Linux (x86_64 or ARM64); macOS is CPU-only
- Multi-GPU
mgpu target requires MPI
- Kernel code must use a restricted Python subset; NumPy/SciPy are not
allowed inside kernels
- QPU access requires provider-specific credentials and accounts
Troubleshooting
- Import error after
pip install cudaq: Ensure Python 3.10+ and a
supported OS (Linux or macOS)
- No GPU detected: Verify CUDA Toolkit is installed and
nvidia-smi
shows your GPU; fall back to qpp-cpu
- Kernel compile error: Check that only supported Python constructs are
used inside
@cudaq.kernel
- QPU submission fails: Confirm credentials are set as environment
variables per the provider docs
