I've heard lots of talk over the past decade about the potential of quantum computing. Most of what I've read about the topic (mostly articles targeted at the layman) focuses on the exponential computational gains that will one day be achieved by linking together more and more qubits. I don't know that any of them have directly addressed how long these quantum calculations take to complete or what factors influence how long they take.
My primary reason for asking is the following thought chain:
- Measuring one particle in an entangled pair of particles separated by a vast distance can influence subsequent measurements made on the other particle and that influence is faster than the speed of light.
- Quantum entanglement cannot be used to transmit information faster than the speed of light.
- Quantum entanglement is a central component of quantum computing.
- Wait a second... Is the information processing performed by a hypothetical "distributed quantum computer" subject to classical light speed limitations?
To restate the question slightly, does the information encoded in and processed by the superposition of the entangled qubits interact with all or some of the qubits in the system during a calculation? If so, can this information be considered to be traveling between these physically separated qubits? If so, does the physical distance between qubits influence the speed of the calculation?
If the physical distance separating the qubits of a quantum computer doesn't influence the speed of the computation, how can we say that these qubits aren't passing actual, unambiguously real information back and forth faster than the speed of light?
If the physical distance does influence the speed of the computation, please just tell me so that I can stop thinking about this...