Programming quantum computers require awareness of entanglement, the phenomenon in which measurement outcomes of qubits are correlated. Entanglement can determine the correctness of algorithms and the suitability of programming patterns.
Entangled qubits give rise to Einstein’s characterization of “spooky action at a distance.” But that potency is equal parts a source of weakness. While programming, discarding one qubit without being aware of its entanglement with one more qubit can obliterate the information put away in the other, endangering the accuracy of the program.