Firstly, I apologise for any lack of understanding, incorrect assumptions or misinterpretations of the very little I know about physics, quantum mechanics & quantum computing. I am not an academic, scientist or mathematician, but a software engineer with an interest in quantum computing and cryptography. With that in mind, my question may be stupid, but I was always told there's "no such thing as a stupid question" so I'll ask it anyway. My very little understanding of quantum mechanics and superposition (and please correct me if I've got any of this wrong) is that the state of a quantum particle is not determined until it is observed, as proven by the double slit experiment, so in terms of quantum computing, a qubit can be both a zero and a one at the same time. Does this mean that, for example, a 4 character string represented by qubytes with its qubits in an undetermined state would effectively be every combination that a 4 character string could be, at the same time? Would that mean that theoretically a quantum computer with enough qubytes could guess a password in a single attempt by using a qubyte string with its qubits in an undetermined state? If the above were true , how would observation of the qubit states work? If my understanding is correct, then observation of the qubyte string BEFORE attempting to guess the password would cause the qubits to get determined values therefore creating a string e.g. "abcd". But if the qubits were not observed and therefore in an undetermined state, and that string was used to guess the password (let's assume the password is "four"), if I observed the qubit states AFTER the password was guessed, would they reflect the value of the password i.e "four"?