> ## Documentation Index
> Fetch the complete documentation index at: https://prod-mint.classiq.io/llms.txt
> Use this file to discover all available pages before exploring further.
# Power
The *power* statement applies the unitary operation raised to some integer power,
where the unitary is specified as a nested statement block.
## Syntax
[comment]: DO_NOT_TEST
```python theme={null}
def power(exponent: CInt, stmt_block: QCallable) -> None:
pass
```
**power** **(** *exponent* **)** **\{** *statements* **}**
## Semantics
* If the statement block specifies the unitary operation $U$ on some quantum object,
*power* applies $U^{exponent}$.
* In the general case, the statement block is iterated over *exponent* times, but in some important
special cases the operation is implemented more efficiently.
* Quantum variables declared outside the *power* statement and used inside its nested
block must be initialized prior to it and remain initialized subsequently.
* Quantum variables declared inside the *power* statement, including in
nested function calls, must be uninitialized at the end of the statement.
## Examples
In the following example `power` is applied 3 times - to gate-level functions `H` and `RX`,
and to a user-defined function `foo`. It demonstrates both special and general treatment
of the *power* operation.
```python theme={null}
from classiq import *
from classiq.qmod.symbolic import pi
@qfunc
def foo(p: CInt, q: QBit):
power(p, lambda: H(q))
power(p, lambda: PHASE(pi / 8, q))
@qfunc
def main(q: Output[QBit]):
allocate(q)
power(2, lambda: foo(5, q))
```
```
qfunc foo(p: int, q: qbit) {
power (p) {
H(q);
}
power (p) {
PHASE(pi / 8, q);
}
}
qfunc main() {
q: qbit;
allocate(q);
power (2) {
foo(5, q);
}
}
```
Synthesizing this model creates the quantum program shown below.
Because two consecutive applications of `H` cancel each other out, raising `H` to the power
of 5 is equivalent to applying `H` once. Raising `RX` with rotation angle $\pi / 8$ to the
power 5 is equivalent to applying `RX` with rotation angle $5 \times \pi / 8$. However, raising
`foo` to the power 2 requires 2 consecutive applications of `foo`.
