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There is certainly a very valid concern in your question. Yes, there are physical processes which, assuming quantum mechanics to be true, give us perfect randomness that is completely unpredictable to anyone. It's as simple as a beamsplitter that can perform a 50:50 split of photons into two different directions. The issue is, if you are buying such a device ...


"our knowledge of quantom behavior is not that perfect" -- I would disagree. Sometimes, the fact that quantum behavior "can't be predicted", or some of the claims in popular media ("entanglement is spooky!" / "Mysterious quantum process...!") lead people to think that quantum mechanics isn't well understood. It is! The ...


Note that you do not measure anything before sending to QC. What you actually send to QC is a sequence of instructions telling QC what to do. The measurement is the last instruction necessary for obtaining results as pointed out in the other answer.


The simple answer is that you can't get the statevector information out of a real quantum computer; or, more generally, a quantum system. For the real computer to extract information from the qubits, they have to collapse to some basis state $\left(|0\rangle \; \text{or} \; |1\rangle \right)$. And this collapse is performed by measuring the qubits.


The article of Devoret and Schoelkopf [1] and an update provided in Section 7.1 of Reagor [2] makes a comparison between Moore's law and an observed trend of exponentially improving $T_1$ and $T_2$ times for superconducting qubits. The trend they present shows a roughly exponential improvement from $10^0$ to $10^6$ nanoseconds for $T_2$ between various ...


The quantum gates in a superconducting qubit chip are not devices located in space made out of metal. They are processes applied over time. They look like carefully choreographed microwave chirps travelling down wires attached to the superconducting loops that are the qubits. Instead of moving the data through the operations, you move the operations through ...

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