.. _getting_started:

Getting Started
===============

The |IQSDK| is a complete quantum computing stack using simulation.
It gives developers the programming tools for developing applications that
incorporate results from quantum algorithms.

Included are a quantum compiler, quantum runtime, language extensions, and
a suite of qubit simulator backends (ranging from abstract to physics-based). The language extensions provide the data
types to represent quantum resources and build powerful quantum expressions.
The quantum compiler comprehends that logic, and optimizes the
quantum instructions to reduce the number and complexity. The quantum runtime enables the
dynamic flow of data between the qubit simulator backend and the C++ data
structures. And the qubit simulators apply various simulation techniques to
return a result from a given quantum system.

Users can find information here to:
* Get familiar with new tools and quantum computing concepts.
* Check on hardware :ref:`requirements <system_reqs>`.
* Learn about :ref:`how to use <usage>` the SDK.

.. _system_reqs:

System Requirements
-------------------

The |IQSDK| has the following memory requirements:

.. _mem_reqs:

Memory Requirements
^^^^^^^^^^^^^^^^^^^

The memory requirement of applications compiled using the |IQSDK| will be the
sum of the traditional footprint created by the data structure in the C++ code
and the memory required by the qubit simulator.

The backends utilizing state-vector simulations require an amount of memory
which increases with the number of qubits.
Representing :math:`n` qubits requires :math:`2^n`
complex numbers. Representing a complex ``double`` value requires 16 bytes, :math:`2^4`. So
the memory required to simulate :math:`n` qubits is

.. math::

   \text{memory} = 2^{(4 + n)} \, \text{bytes}


As an example, simulating different-sized qubit systems will require at least:

.. list-table:: Memory Requirements
   :header-rows: 1
   :class: longtable

   * - qubits
     - memory

   * - 10
     - 17 KB

   * - 20
     - 17 MB

   * - 30
     - 17.2 GB

Note that adding 1 additional qubit doubles the required memory.

.. _usage:

How to Use?
-----------

In the simplest terms, using the |IQSDK| follows the pattern:

1. Write the quantum algorithm with a ``.cpp`` extension as a separate file.
   This file will include the ``quantum_kernel`` definitions, initialization for
   quantum hardware, and the logic for the quantum/classical algorithms
   (see :ref:`Writing New Algorithms<new_algos>` section for details).
   Example: ``my_new_algo.cpp``

2. Build and Run.
   Invoke the ``intel-quantum-compiler`` to use the |IQSDK|:

   .. code-block:: console

      $ ./intel-quantum-compiler [compiler flags] new_algo_start_here.cpp


   To see a list of the flag options, run

   .. code-block:: console

      $ ./intel-quantum-compiler -h


   Run the executable produced by the compiler:

   .. code-block:: console

      $ ./new_algo_start_here

See |DGR:Issues| for the limitations.