# Circuit Construction#

The circuit construction module allows the user to implement low level functions to integrate them in routines of higher complexity. For classical languages, this is a common feature of many compilers.
Since QuantumSession is an inheritor of QuantumCircuit, it also exposes an append method, implying that once a QuantumCircuit is created it can be smoothly integrated into Qrisps high-level infrastructure using the `to_gate`

method:

```
from qrisp import QuantumCircuit
from third_party_qiskit_module import some_quantum_function_qc
def some_quantum_function(qv, parameters):
qc = QuantumCircuit.from_qiskit(some_quantum_function_qc(parameters))
qv.qs.append(qc.to_gate(), qv)
```

This snippet demonstrates how a Qiskit quantum circuit generated by a third party module can be turned into a Qrisp function of a QuantumVariable.

There are 5 important classes here:

The QuantumCircuit class, which describes quantum circuits in a very similar way as Qiskit (ie. it contains a list of qubit objects, a list of classical bit objects and a list of instructions)

The Operation class, which corresponds to the gate object from Qiskit. This class describes arbitrary gates and measurements.

The Instruction class, which combines Operation objects and the qubit/classical bits it operates on.

The Qubit class, which represents qubits.

The Clbit class, which represents classical bits.

Note

In order to allow an easy transition, this module’s architecture and naming is close to Qiskit.