CirQ/en

Developed by Google, CirQ is an open-source quantum computing library to build, optimize, simulate, and run quantum circuits. More specifically, CirQ allows for the simulation of circuits on particular qubit configurations, which can optimize a circuit for a certain qubit architecture. Information on the features can be found in the CirQ documentation and GitHub. Like Snowflurry, CirQ can be used to run quantum circuits on the MonarQ quantum computer.

Installation¶

The CirQ simulator is available on all of our clusters. To have access, you must load the Python language.

Note

It is preferable to work in a Python virtual environment.

module load python/3.11
virtualenv --no-download --clear ~/ENV && source ~/ENV/bin/activate
pip install --no-index --upgrade pip
pip install --no-index cirq==1.4.1
python -c "import cirq"
pip freeze > cirq-1.4.1-reqs.txt

The last command creates the cirq-1.4.1-reqs.txt file, which you can also use in a job script, such as in the example below.

Running on a Cluster¶

script.sh

#!/bin/bash
#SBATCH --account=def-someuser # Modify with your account name
#SBATCH --time=00:15:00        # Modify as needed
#SBATCH --cpus-per-task=1      # Modify as needed
#SBATCH --mem-per-cpu=1G       # Modify as needed

# Load modules dependencies.
module load StdEnv/2023 gcc python/3.11 

# Generate your virtual environment in $SLURM_TMPDIR.                                                                                           
virtualenv --no-download ${SLURM_TMPDIR}/env                                                                                                                   
source ${SLURM_TMPDIR}/env/bin/activate  

# Install CirQ and its dependencies.                                                                                                                                                                                                                                                                                  
pip install --no-index --upgrade pip                                                                                                                            
pip install --no-index --requirement ~/cirq-1.4.1-reqs.txt

# Edit with your CirQ program.                                                                                                                                                             
python cirq_example.py

You can then submit your job to the scheduler.

Use case: Bell states¶

Bell states are the simplest states that allow for the explanation of both superposition and entanglement on qubits. The CirQ library allows for the construction of a Bell state as follows:

python> import cirq
python> from cirq.contrib.svg import SVGCircuit
python> from cirq import H, CNOT

python> qubits = cirq.LineQubit.range(2)
python> circuit = cirq.Circuit(H.on(qubits[0]),CNOT.on(qubits[0],qubits[1]))
python> circuit.append(cirq.measure(qubits, key='m'))
python> SVGCircuit(circuit)

This code builds and displays a circuit that prepares a Bell state. The H gate (Hadamard gate) creates an equal superposition of |0⟩ and |1⟩ on the first qubit, while the CNOT gate (controlled X gate) creates an entanglement between the two qubits. This Bell state is therefore an equal superposition of the states |00⟩ and |11⟩. Simulating this circuit using CirQ allows you to visualize the results. In this diagram, the integer 3 represents the state |11⟩ since 3 is written 11 in binary.

```python python> import matplotlib.pyplot as plt python> s = cirq.Simulator().run(circuit, repetitions=1000) python> counts = s.histogram(key='m') python> cirq.plot_state_histogram(counts, plt.subplot())