# Z gate (CUDA-Q)
[[z-gate|Z gate]] implementation using CUDA-Q. The Z gate applied to $\lvert 0\rangle$ is invisible at measurement (it leaves $\lvert 0\rangle$ unchanged), so this example prepares $\lvert +\rangle$ first, applies Z, then rotates back to the computational basis to confirm the phase flip.

```cpp
// Compile: nvq++ main.cpp -o main
// Run:     ./main

#include <cudaq.h>

struct kernel {
    __qpu__ void operator()() {
        cudaq::qubit q;
        h(q);  // |0> -> |+>
        z(q);  // |+> -> |->
        h(q);  // rotate back to computational basis: |-> -> |1>
        mz(q);
    }
};

int main() {
    auto counts = cudaq::sample(kernel{});
    counts.dump();  // 100% |1>, confirming the phase flip
}
```