# Do states get entangled in Grover’s algorithm?

I am new to QC and right now trying to understand Grover’s algorithm. In Qiskit documents, in the section about solving Sudoku using Grover’s, the first step is explained to be creating three register: $$|x\rangle$$ $$|c\rangle$$ and $$|out\rangle$$

The next step is to initialize $$|x\rangle$$ by $$H|0\rangle$$. I get up to here.

Then we apply controlled Not gates to flip the $$|c\rangle$$ (clause) registers. Here I am stuck because I thought doing a CNOT on $$|0+\rangle$$ leads to entangled states.

The Qiskit document is here:

https://qiskit.org/textbook/ch-algorithms/grover.html

Do the states really get entangled and if so how can the rest of the circuit work whilst considering the individual qubits?

• Hi and welcome to Quantum Computing SE. Could you please add link to the document you are asking about? Feb 12, 2021 at 7:05
• The algorithm must have some entanglement somewhere. You do not consider just individual qubits, but the global state of the system. Feb 12, 2021 at 7:40
• Hello Martin. Thank you. I added a link to the document. Mar 3, 2021 at 0:59