User guide
Contents
User guide#
This guide illustrates the main features of Qiskit on IQM. You are encouraged to run the demonstrated code snippets and check the output yourself.
Note
At the moment IQM does not provide a quantum computing service open to the general public. Please contact our sales team to set up your access to an IQM quantum computer.
Hello, world!#
Here’s the quickest and easiest way to execute a small computation on an IQM quantum computer and check that things are set up correctly:
Download the bell_measure.py example file
Install Qiskit on IQM as instructed below (feel free to skip the import statement)
Install Cortex CLI and log in as instructed in the documentation
Set the environment variable as instructed by Cortex CLI after logging in
Run
$ python bell_measure.py --server_url https://demo.qc.iqm.fi/cocos– replace the example URL with the correct oneIf you’re connecting to a real quantum computer, the output should show almost half of the measurements resulting in ‘00’ and almost half in ‘11’ – if this is the case, things are set up correctly!
Installation#
The recommended way is to install the distribution package qiskit-iqm directly from the
Python Package Index (PyPI):
$ pip install qiskit-iqm
After installation Qiskit on IQM can be imported in your Python code as follows:
import qiskit_iqm
Running a quantum circuit on an IQM quantum computer#
In this section we demonstrate the practicalities of using Qiskit on IQM on an example of constructing and executing a simple quantum circuit on an IQM quantum computer.
Let’s consider the following quantum circuit which prepares and measures a GHZ state:
from qiskit import QuantumCircuit
qc = QuantumCircuit(3, 3)
qc.h(0)
qc.cx(0, 1)
qc.cx(0, 2)
qc.measure_all()
print(qc.draw(output='text'))
┌───┐ ░ ┌─┐
q_0: ┤ H ├──■────■───░─┤M├──────
└───┘┌─┴─┐ │ ░ └╥┘┌─┐
q_1: ─────┤ X ├──┼───░──╫─┤M├───
└───┘┌─┴─┐ ░ ║ └╥┘┌─┐
q_2: ──────────┤ X ├─░──╫──╫─┤M├
└───┘ ░ ║ ║ └╥┘
meas_0: ═══════════════════╩══╬══╬═
║ ║
meas_1: ══════════════════════╩══╬═
║
meas_2: ═════════════════════════╩═
To execute this circuit against an IQM quantum computer you need to initialize an appropriate Qiskit backend instance
that represents the IQM quantum computer under use, and simply use Qiskit’s execute function as normal:
from qiskit import execute
from qiskit_iqm import IQMProvider
provider = IQMProvider(iqm_server_url)
backend = provider.get_backend()
job = execute(qc, backend, shots=1000)
print(job.result().get_counts())
Note that the code snippet above assumes that you have set the variable iqm_server_url.
If the IQM server you are connecting to requires authentication, you will also have to use
Cortex CLI to retrieve and automatically refresh access tokens,
then set the IQM_TOKENS_FILE environment variable to use those tokens.
See Cortex CLI’s documentation for details.
Alternatively, authorize with the IQM_AUTH_SERVER, IQM_AUTH_USERNAME and IQM_AUTH_PASSWORD environment variables
or pass them as arguments to the constructor of IQMProvider, however this approach is less secure
and considered as deprecated.
The backend instance we created above provides all the standard backend functionality that one expects from a
backend in Qiskit. For this example, I am connected to an IQM backend that features a 5-qubit chip with star-like
connectivity:
QB1
|
QB2 - QB3 - QB4
|
QB5
Let’s examine its basis gates and the coupling map through the backend instance
print(f'Native operations of the backend: {backend.operation_names}')
print(f'Coupling map of the backend: {backend.coupling_map}')
Native operations of the backend: ['r', 'cz', 'measure']
Coupling map of the backend: [[0, 2], [1, 2], [2, 3], [2, 4]]
At IQM we identify qubits by their names, e.g. ‘QB1’, ‘QB2’, etc. as demonstrated above. In Qiskit, qubits are
identified by their indices in the quantum register, as you can see from the printed coupling map above. Most of the
time you do not need to deal with IQM-style qubit names when using Qiskit, however when you need, the methods
IQMBackend.qubit_name_to_index() and IQMBackend.index_to_qubit_name() can become handy.
Now we can study how the circuit gets transpiled:
from qiskit.compiler import transpile
qc_transpiled = transpile(qc, backend=backend, layout_method='sabre', optimization_level=3)
print(qc_transpiled.draw(output='text'))
global phase: π/2
┌────────────┐┌────────┐ ┌────────────┐┌────────┐ ░ ┌─┐
q_2 -> 0 ┤ R(π/2,π/2) ├┤ R(π,0) ├─────────■───────┤ R(π/2,π/2) ├┤ R(π,0) ├─░───────┤M├
└────────────┘└────────┘ │ └────────────┘└────────┘ ░ └╥┘
ancilla_0 -> 1 ─────────────────────────────────┼─────────────────────────────────────────╫─
┌────────────┐┌────────┐ │ ░ ┌─┐ ║
q_0 -> 2 ┤ R(π/2,π/2) ├┤ R(π,0) ├─■───────■────────────────────────────────░─┤M├────╫─
└────────────┘└────────┘ │ ░ └╥┘ ║
ancilla_1 -> 3 ─────────────────────────┼───────────────────────────────────────────╫─────╫─
┌────────────┐┌────────┐ │ ┌────────────┐ ┌────────┐ ░ ║ ┌─┐ ║
q_1 -> 4 ┤ R(π/2,π/2) ├┤ R(π,0) ├─■─┤ R(π/2,π/2) ├──┤ R(π,0) ├─────────────░──╫─┤M├─╫─
└────────────┘└────────┘ └────────────┘ └────────┘ ░ ║ └╥┘ ║
c_0: ═════════════════════════════════════════════════════════════════════╬══╬══╬═
║ ║ ║
c_1: ═════════════════════════════════════════════════════════════════════╬══╬══╬═
║ ║ ║
c_2: ═════════════════════════════════════════════════════════════════════╬══╬══╬═
║ ║ ║
meas_0: ═════════════════════════════════════════════════════════════════════╩══╬══╬═
║ ║
meas_1: ════════════════════════════════════════════════════════════════════════╩══╬═
║
meas_2: ═══════════════════════════════════════════════════════════════════════════╩═
We can also simulate the execution of the transpiled circuit before actually executing it:
from qiskit import Aer
simulator = Aer.get_backend('qasm_simulator')
job = execute(qc_transpiled, simulator, shots=1000)
print(job.result().get_counts())
More advanced examples#
In this section we demonstrate some less simple examples of using Qiskit on IQM and its interoperability with various tools available in Qiskit.
It is possible to run multiple circuits at once, as a batch. In many scenarios this is more time efficient than running the circuits one by one. For batch execution there are some restriction that we shall keep in mind, namely all circuits have to measure the same qubits, and all circuits will be executed for the same number of shots. For starters, let’s construct two circuits preparing and measuring different Bell states:
qc_1 = QuantumCircuit(2)
qc_1.h(0)
qc_1.cx(0, 1)
qc_1.measure_all()
qc_2 = QuantumCircuit(2)
qc_2.h(0)
qc_2.x(1)
qc_2.cx(0, 1)
qc_2.measure_all()
Now, we can execute them together in a batch:
job = execute([qc_1, qc_2], backend, initial_layout=[0, 2], shots=1000)
print(job.result().get_counts())
The batch execution functionality can be used to run a parameterized circuit for various concrete values of parameters:
import numpy as np
from qiskit.circuit import Parameter
qc = QuantumCircuit(2)
theta = Parameter('theta')
theta_range = np.linspace(0, 2*np.pi, 3)
qc.h(0)
qc.cx(0, 1)
qc.rz(theta, [0, 1])
qc.cx(0, 1)
qc.h(0)
qc.measure_all()
qc_transpiled = transpile(qc, backend=backend, layout_method='sabre', optimization_level=3)
circuits = [qc_transpiled.bind_parameters({theta: n}) for n in theta_range]
job = execute(circuits, backend, shots=1000, optimization_level=0)
print(job.result().get_counts())
Note that it is important to transpile the parameterized circuit before binding the values to ensure a consistent qubit measurements across circuits in the batch.
How to develop and contribute#
Qiskit on IQM is an open source Python project. You can contribute by creating GitHub issues to report bugs or request new features, or by opening a pull request to submit your own improvements to the codebase.
To start developing the project, clone the GitHub repository and install it in editable mode with all the extras:
$ git clone git@github.com:iqm-finland/qiskit-on-iqm.git
$ cd qiskit-on-iqm
$ pip install -e ".[dev,docs,testing]"
To be able to build the docs graphviz has to be installed. Then to build and view the docs run:
$ tox -e docs
$ firefox build/sphinx/html/index.html
Run the tests:
$ tox
Tagging and releasing#
After implementing changes to Qiskit on IQM one usually wants to release a new version. This means that after the changes are merged to the main branch
the repository should have an updated
CHANGELOG.rstwith information about the new changes,the latest commit should be tagged with the new version number,
and a release should be created based on that tag.
The last two steps are automated, so one needs to worry only about properly updating the CHANGELOG. It should be done along with the pull request which is introducing the main changes. The new version must be added on top of all existing versions and the title must be “Version MAJOR.MINOR”, where MAJOR.MINOR represents the new version number. Please take a look at already existing versions and format the rest of your new CHANGELOG section similarly. Once the pull request is merged into main, a new tag and a release will be created automatically based on the latest version definition in the CHANGELOG.