### Test qsimcirq Installation

Source: https://quantumai.google/qsim/install_qsimcirq

After installation, copy the provided test file to your machine and run pytest to verify the installation. This command also serves as an example of how to use qsimcirq.

```bash
python3 -m pytest qsimcirq_test.py
```

--------------------------------

### Install Cirq and qsimcirq

Source: https://quantumai.google/qsim/tutorials/qsimcirq

Installs the necessary Cirq and qsimcirq packages. It checks for existing installations and installs them quietly if not found.

```python
import time

try:
    import cirq
except ImportError:
    !pip install cirq --quiet
    import cirq

try:
    import qsimcirq
except ImportError:
    !pip install qsimcirq --quiet
    import qsimcirq

```

--------------------------------

### Install Cirq and qsimcirq

Source: https://quantumai.google/qsim/tutorials/noisy_qsimcirq

Installs the necessary Cirq and qsimcirq packages if they are not already present. This is a prerequisite for running the tutorial.

```python
try:
    import cirq
except ImportError:
    !pip install cirq --quiet
    import cirq

try:
    import qsimcirq
except ImportError:
    !pip install qsimcirq --quiet
    import qsimcirq
```

--------------------------------

### Verify qsim GPU Installation

Source: https://quantumai.google/qsim/tutorials/gcp_gpu

Verifies the qsim installation by importing the qsim_gpu module. A successful import indicates that the GPU-enabled version was compiled and installed correctly.

```python
python3 -c "import qsimcirq; print(qsimcirq.qsim_gpu)"

```

--------------------------------

### Start qsim Docker container

Source: https://quantumai.google/qsim/tutorials/gcp_cpu

Run this command on your VM to start the qsim Docker container. It mounts the current directory to `/homedir` inside the container and maps port 8888. The `&` runs the container in the background.

```bash
docker run -v `pwd`:/homedir -p 8888:8888 gcr.io/quantum-builds/github.com/quantumlib/jupyter_qsim:latest &

```

--------------------------------

### X Gate Example

Source: https://quantumai.google/qsim/input_format

Example of applying an X gate to a qubit.

```text
2 x 2
```

--------------------------------

### S Gate Example

Source: https://quantumai.google/qsim/input_format

Example of applying an S gate to a qubit.

```text
2 s 1
```

--------------------------------

### Install Build Tools for qsim

Source: https://quantumai.google/qsim/tutorials/gcp_gpu

Installs CMake, pip, and pybind11, which are required to build the qsim library. This command ensures all necessary development tools are present.

```bash
sudo apt install cmake && sudo apt install pip && pip install pybind11

```

--------------------------------

### Install Development Dependencies

Source: https://quantumai.google/qsim/install_qsimcirq

Use these commands to install development dependencies if you plan to develop qsimcirq. Ensure you have pip version 25.1 or higher.

```bash
pip install -r requirements.txt
```

```bash
pip install --group dev
```

--------------------------------

### Verify qsim Installation and Run Simulation

Source: https://quantumai.google/qsim/tutorials/gcp_cpu

This Python code verifies your qsim installation by creating a simple quantum circuit, simulating it using qsimcirq, and printing the results. Paste this code into the REPL or a file within your connected container.

```python
# Import Cirq and qsim
import cirq
import qsimcirq

# Instantiate qubits and create a circuit
q0, q1 = cirq.LineQubit.range(2)
circuit = cirq.Circuit(cirq.H(q0), cirq.CX(q0, q1))

# Instantiate a simulator that uses the GPU
qsim_simulator = qsimcirq.QSimSimulator()

# Run the simulation
print("Running simulation for the following circuit:")
print(circuit)

qsim_results = qsim_simulator.compute_amplitudes(
    circuit, bitstrings=[0b00, 0b01])

print("qsim results:")
print(qsim_results)

```

--------------------------------

### Install qsimcirq and Cirq

Source: https://quantumai.google/qsim/qsimcirq_tutorial

Install the necessary libraries for using qsimcirq with Cirq. Ensure you are using compatible versions.

```shell
%%shell
pip install cirq==0.8.2 --quiet
pip install qsimcirq==0.3.0 --quiet

```

--------------------------------

### Install Cirq and qsimcirq

Source: https://quantumai.google/qsim/tutorials/q32d14

Installs the necessary Cirq and qsimcirq packages. Includes checks to avoid reinstalling if already present.

```python
import time

import numpy as np

try:
    import cirq
except ImportError:
    !pip install cirq --quiet
    import cirq

try:
    import qsimcirq
except ImportError:
    !pip install qsimcirq --quiet
    import qsimcirq

```

--------------------------------

### QSimSimulator Execution Output

Source: https://quantumai.google/qsim/tutorials/q32d14

Example output from the QSimSimulator, showing computed amplitudes and execution times.

```text
Result: [(-3.869717602356104e-06-5.219020749791525e-06j), (7.610328793816734e-06+9.70489600149449e-06j)]
Wall Time: 147.6608045989999   -- Process Time: 2295.0433410680002

```

--------------------------------

### Install CUDA Toolkit

Source: https://quantumai.google/qsim/tutorials/gcp_gpu

Installs the NVIDIA CUDA toolkit, which is necessary for GPU acceleration. This command should be run on the virtual machine.

```bash
sudo apt install -y nvidia-cuda-toolkit

```

--------------------------------

### Example gcloud Configuration Output

Source: https://quantumai.google/qsim/tutorials/qsimcirq_gcp

An example of the output from `gcloud config list`, showing the active region, zone, account, and project settings.

```text
region = us-east4
zone = us-east4-c
[core]
account = wellhello@gargle.com
disable_usage_reporting = False
project = quantum-22222
```

--------------------------------

### Handling Intermediate Measurements with qsimcirq

Source: https://quantumai.google/qsim/tutorials/qsimcirq

Demonstrates simulating a circuit with intermediate measurements using qsimcirq's QSimSimulator. This example shows how qsim correctly handles circuits where measurements occur before the circuit's end, ensuring accurate sampling for each repetition.

```python
# Define a circuit with intermediate measurements.
q0 = cirq.LineQubit(0)
circuit = cirq.Circuit(
    cirq.X(q0) ** 0.5,
    cirq.measure(q0, key="m0"),
    cirq.X(q0) ** 0.5,
    cirq.measure(q0, key="m1"),
    cirq.X(q0) ** 0.5,
    cirq.measure(q0, key="m2"),
)
print("Circuit:")
print(circuit)
print()

# Simulate the circuit with qsim and return just the measurement values.
print("qsim results:")
qsim_simulator = qsimcirq.QSimSimulator()
qsim_results = qsim_simulator.run(circuit, repetitions=5)
print(qsim_results)


```

```text
Circuit:
0: ───X^0.5───M('m0')───X^0.5───M('m1')───X^0.5───M('m2')───

qsim results:
m0=00110
m1=11111
m2=10001


```

--------------------------------

### Install qsimcirq on Linux

Source: https://quantumai.google/qsim/install_qsimcirq

Install the qsimcirq Python package on Linux. This command automatically checks for CUDA and GPUs and attempts to build a GPU-accelerated version if available.

```bash
pip3 install qsimcirq
```

--------------------------------

### Square Root of W Gate Example

Source: https://quantumai.google/qsim/input_format

Example of applying the square root of W gate (√W), equivalent to Rx,y(π/4, π/2), to a qubit.

```text
1 hz_1_2 1
```

--------------------------------

### Verify qsim GPU Usage with Cirq

Source: https://quantumai.google/qsim/tutorials/gcp_gpu

This code snippet demonstrates how to use qsim with GPU acceleration. It sets up a simple circuit and runs it using a QSimSimulator configured for GPU. Adjust 'mode' or 'num_gpus' based on your setup (Option 1/2 vs. Option 3).

```python
# Import Cirq and qsim
import cirq
import qsimcirq

# Instantiate qubits and create a circuit
q0, q1 = cirq.LineQubit.range(2)
circuit = cirq.Circuit(cirq.H(q0), cirq.CX(q0, q1))

# Instantiate a simulator that uses the GPU
# Option 1 (mode=0) or Option 2 (mode=1)
gpu_options = qsimcirq.QSimOptions(use_gpu=True, gpu_mode = mode, max_fused_gate_size=4)
# Option 3 (number of GPUs = `num_gpus`)
gpu_options = qsimcirq.QSimOptions(disable_gpu=False, gpu_mode = num_gpus, max_fused_gate_size=4)
qsim_simulator = qsimcirq.QSimSimulator(qsim_options=gpu_options)

# Run the simulation
print("Running simulation for the following circuit:")
print(circuit)

qsim_results = qsim_simulator.compute_amplitudes(
    circuit, bitstrings=[0b00, 0b01])

print("qsim results:")
print(qsim_results)

```

--------------------------------

### Navigate to Tutorial Directory

Source: https://quantumai.google/qsim/tutorials/multinode

Change the current directory to the multinode tutorial directory within the cloned qsim repository.

```bash
cd qsim/docs/tutorials/multinode
```

--------------------------------

### Simulate Quantum Circuit with QSimSimulator

Source: https://quantumai.google/qsim/tutorials/qsimcirq_gcp

Instantiate the QSimSimulator and use it to simulate the previously defined quantum circuit. This demonstrates running a simulation on your VM.

```python
simulator = qsimcirq.QSimSimulator()
result = simulator.simulate(circuit)
print("Result:")
print(result)
```

--------------------------------

### Run Sample Simulation with AVX and OpenMP

Source: https://quantumai.google/qsim/bazel

Execute a sample simulation using the `apps:qsim_base` target with AVX and OpenMP optimizations. Ensure the `circuit_q24` file is specified correctly.

```bash
bazel run --config=avx --config=openmp apps:qsim_base -- -c circuits/circuit_q24

```

--------------------------------

### Y Gate Example

Source: https://quantumai.google/qsim/input_format

Example of applying a Y gate to a qubit.

```text
3 y 3
```

--------------------------------

### T Gate Example

Source: https://quantumai.google/qsim/input_format

Example of applying a T gate to a qubit.

```text
1 t 1
```

--------------------------------

### Configure QSimSimulator Options

Source: https://quantumai.google/qsim/cirq_interface

Instantiate QSimSimulator with custom options for CPU threads, verbosity, and denormal number handling.

```python
qsim_options = qsimcirq.QSimOptions(cpu_threads=8, verbosity=0, denormals_are_zeros=True)
my_sim = qsimcirq.QSimSimulator(qsim_options)
myres = my_sim.simulate(program=my_circuit)
```

--------------------------------

### Z Gate Example

Source: https://quantumai.google/qsim/input_format

Example of applying a Z gate to a qubit.

```text
4 z 4
```

--------------------------------

### Basic Bazel Test Run

Source: https://quantumai.google/qsim/bazel

Run all qsim tests with the default build configuration. This is the basic command for building and testing.

```bash
bazel test tests:all

```

--------------------------------

### Hadamard Gate Example

Source: https://quantumai.google/qsim/input_format

Example of applying a Hadamard gate to a qubit.

```text
0 h 0
```

--------------------------------

### Initialize QSimSimulator with GPU options

Source: https://quantumai.google/qsim/tutorials/amd_gpu

Instantiate the QSimSimulator for AMD Instinct GPUs. Ensure `use_gpu` is true and `gpu_mode` is set to 0.

```python
simulator = qsimcirq.QSimSimulator(qsim_options=qsimcirq.QSimOptions(
        use_gpu=True,
        gpu_mode=0,
        ...
    ))

```

--------------------------------

### Identity (2-qubit) Gate Example

Source: https://quantumai.google/qsim/input_format

Example of applying a 2-qubit Identity gate.

```text
8 id2 0 1
```

--------------------------------

### Identity (1-qubit) Gate Example

Source: https://quantumai.google/qsim/input_format

Example of applying a 1-qubit Identity gate.

```text
7 id1 0
```

--------------------------------

### Compute Amplitudes with QSimhSimulator (Initial Options)

Source: https://quantumai.google/qsim/qsimcirq_tutorial

Initializes the QSimhSimulator with specified options and computes amplitudes for a given circuit and bitstrings. Useful for exploring specific simulation configurations.

```python
qsimh_simulator = qsimcirq.QSimhSimulator(options)
results_0 = qsimh_simulator.compute_amplitudes(
    circuit, bitstrings=[0b00, 0b01, 0b10, 0b11])
print(results_0)
```

--------------------------------

### iSwap Gate Example

Source: https://quantumai.google/qsim/input_format

Example of applying an iSwap gate to two qubits.

```text
4 is 6 7
```

--------------------------------

### CNOT Gate Example

Source: https://quantumai.google/qsim/input_format

Example of applying a CNOT gate to two qubits.

```text
3 cnot 4 5
```

--------------------------------

### Initialize Google Cloud SDK

Source: https://quantumai.google/qsim/tutorials/qsimcirq_gcp

Initialize the Google Cloud SDK on your local machine to manage GCP resources and connect to your VM. This command prompts for your project ID and zone.

```bash
$ gcloud init
```

--------------------------------

### CZ Gate Example

Source: https://quantumai.google/qsim/input_format

Example of applying a CZ gate to two qubits.

```text
2 cz 2 3
```

--------------------------------

### Measurement (n-qubit) Gate Example

Source: https://quantumai.google/qsim/input_format

Example of applying a measurement gate to multiple qubits.

```text
9 m 0 1 2 3
```

--------------------------------

### Square Root of Y Gate Example

Source: https://quantumai.google/qsim/input_format

Example of applying a square root of Y gate (√Y) to a qubit.

```text
6 y_1_2 6
```

--------------------------------

### Simulate circuit with QSimSimulator options

Source: https://quantumai.google/qsim/cirq_interface

Instantiate QSimSimulator with custom options for CPU threads and verbosity. The simulate method then executes the defined Cirq circuit.

```python
# equivalent to {'t': 8, 'v': 0}
qsim_options = qsimcirq.QSimOptions(cpu_threads=8, verbosity=0)
my_sim = qsimcirq.QSimSimulator(qsim_options)
myres = my_sim.simulate(program=my_circuit)
```

--------------------------------

### CPhase Gate Example

Source: https://quantumai.google/qsim/input_format

Example of applying a CPhase gate with a specified angle φ to two qubits.

```text
6 cp 0 1 0.78
```

--------------------------------

### Tuning qsim Performance with Options

Source: https://quantumai.google/qsim/qsimcirq_tutorial

Demonstrates how to tune qsim performance by passing options to the QSimSimulator constructor, such as specifying the number of threads for parallelization.

```python
# Use eight threads to parallelize simulation.
options = {'t': 8}

qsim_simulator = qsimcirq.QSimSimulator(options)
qsim_start = time.time()
qsim_results = qsim_simulator.simulate(circuit)
qsim_elapsed = time.time() - qsim_start
print(f'qsim runtime: {qsim_elapsed}')
```

--------------------------------

### Rz(φ) Gate Example

Source: https://quantumai.google/qsim/input_format

Example of applying an Rz gate with a specified angle φ to a qubit.

```text
9 rz 9 0.79
```

--------------------------------

### Ry(φ) Gate Example

Source: https://quantumai.google/qsim/input_format

Example of applying an Ry gate with a specified angle φ to a qubit.

```text
8 ry 8 1.05
```

--------------------------------

### Rx(φ) Gate Example

Source: https://quantumai.google/qsim/input_format

Example of applying an Rx gate with a specified angle φ to a qubit.

```text
7 rx 7 0.79
```

--------------------------------

### Run qsim Simulation Binary in Docker

Source: https://quantumai.google/qsim/docker

Once the qsim Docker image is created, use this command to run the qsim_base.x simulation binary. The -v flag is required to mount host directories into the container for accessing circuit files.

```bash
docker run -ti --rm -v $PWD/circuits:/qsim/circuits:ro \
    qsim:latest -c /qsim/circuits/circuit_q24

```

--------------------------------

### fSim Gate Example

Source: https://quantumai.google/qsim/input_format

Example of applying an fSim gate with specified angles θ and φ to two qubits.

```text
5 fs 6 7 3.14 1.57
```