Quantum Computing, Fault Tolerance, Error Correction, Logical Qubits.
On a quantum computer, 2 + 2 is not always 4 — sometimes it may be 3 or 5 or even other values, but on average, given enough runs or shots, 4 will be the most common value — the expectation value. This also means that even with full quantum error correction and perfect logical qubits, shot count