Quantum Computing, Fault Tolerance, Error Correction, Logical Qubits.
total number of physical qubits, but the square root of the number of data qubits, with the remaining physical qubits being stabilizer and flag qubits. An IBM paper which discusses surface codes: Correcting coherent errors with surface codes Sergey Bravyi, Matthias Englbrecht, Robert Koenig, Nolan