On Mon, Jul 30, 2018 at 12:41 AM, <[email protected]> wrote: > > > On Monday, July 30, 2018 at 5:08:24 AM UTC, Jason wrote: >> >> >> >> On Sun, Jul 29, 2018 at 10:30 PM, <[email protected]> wrote: >> >>> >>> >>> On Monday, July 30, 2018 at 3:11:47 AM UTC, Jason wrote: >>>> >>>> >>>> >>>> On Sun, Jul 29, 2018 at 6:44 PM, <[email protected]> wrote: >>>> >>>>> >>>>> >>>>> On Sunday, July 29, 2018 at 11:23:49 PM UTC, [email protected] >>>>> wrote: >>>>>> >>>>>> >>>>>> >>>>>> On Sunday, July 29, 2018 at 10:31:05 PM UTC, Jason wrote: >>>>>>> >>>>>>> Quantum computers represent a disproof of the conjecture that the >>>>>>> wave function is merely a convenience or tool for estimating >>>>>>> probabilities >>>>>>> of experimental outcomes, rather than something that is real. The >>>>>>> reason: >>>>>>> it does things we cannot. >>>>>>> >>>>>>> Jason >>>>>>> >>>>>> >>>>>> Can you be specific? Why does quantum computing depend on both states >>>>>> of a qubit(?) be occupied simultaneously? Can the system toggle between >>>>>> those states, yet not be in both simultaneously? Couldn't quantum >>>>>> computing >>>>>> work, or say be conceptualized with his model? TIA, AG >>>>>> >>>>> >>>>> IOW, is the model of superposition you use in quantum computing a >>>>> necessary condition for its success, or could you use the information-only >>>>> model of the superposition and get the same result. AG >>>>> >>>>>> >>>>>>> >>>>>>> >>>> >>>> In order to explain the final result of the computation appearing in >>>> the measured qubits, each of the intermediate states must have existed and >>>> interacted, >>>> >>> >>> *What are the intermediate states? * >>> >> >> Like a computer program before it prints its result and halts, the >> quantum computer takes advantage of the unmeasured isolated QM system which >> can enter a superposition of many simultaneous states, in the end, before >> the quantum computer prints its result, it must use interference effects to >> get all parts of the wave function to agree before it halts and gets >> measured. If it doesn't then whoever measures the result of the quantum >> computer will become entangled with that multi-valued state (causing that >> observer to split). >> >> >>> >>> *Isn't a qubit system a two-state system? AG* >>> >> >> A qubit will provide only 1 of 2 possible values when measured, but it >> can take on an arbitrarily large number of states within the superposition >> >> > > *But the superposition of a qubit has only two components, and using the > SWE only the probability of these two states change in time. So when > speaking of one qubit, I have no idea what you mean by "an arbitrarily > large number of states within the superposition". AG* > >
To make it clear that the single qubit can enter more than 2 states, consider a system of 20 qubits, used to perform a probabilistic computation in which we expect to see only 1 of 1,000 possible (but equally likely) values (even though the qubits could in theory represent any of 2^20 (~1,000,000) possible combinations of 0 and 1, and even though any single qubit can only be 1 or 0. For each of the 1,000 possible results of the computation, there are 1000 possible final states of the qubit system and possibly more intermediate states. When measured, any individual qubit will read only 1 or 0, but it is more like Qubit 5 is: "1" IFF qubit 3 is "0" and qubit 6 is "1" and qubit 9 is "0" OR qubit 11 is "0" and qubit 12 is "1" and qubit 18 is "1" OR ... (for about 500 or so different cases) "0" IFF qubit 2 is "1" and qubit8 is "0" and qubit 4 is "0" and qubit 16 is "0" OR ... (for about 500 other different cases). So while any given qubit is 1 or 0, it's really in 1000 different states, which when measured will be found to be within one of the 1,000 possible valid states, out of the 1,000,000 possible raw combinations that might be represented by those 20 qubits. > through successive interaction with other qubits, effectively growing >> exponentially. >> >> >> >>> >>> >>>> all the while remaining in a super position (completely isolated from >>>> the environment that contains the quantum computer) for the duration of the >>>> computation. The computation might have been a very long one, and may have >>>> involved vast numbers of states simultaneously held by the qubits during >>>> the computation. Each of these states is designed by the quantum >>>> computation to interfere in such a way to that in most of the branches the >>>> measured qubits will yield the same result. >>>> >>>> We know we can prepare a quantum computation. We know we can measure >>>> the qubits afterwards to get the final answer. >>>> The big question of "what is going on in the middle?" can only be >>>> answered by resorting to asking what the theory can tell us of what the >>>> wave function is doing to perform and implement the computation while we >>>> are not measuring it. >>>> >>> >>> *Since when does QM tell us what is happening to a wf when the system it >>> represents is not being measured? * >>> >> >> This is given by the Schrödinger equation. >> > > *Of course. Right; I was confused by what you were trying to describe. AG* > >> >> >>> >>> *Are you referring to decoherence theory? AG * >>> >> >> No. Decoherence is exactly what you want to avoid within a quantum >> computer. That is the main engineering difficulty, keeping coherence >> (keeping the system of the quantum computer isolated from the rest of the >> environment so that the superposition can be maintained and evolve and >> (from our point of view (being isolated from it)) enter many many states. >> > > *If the superposition of a qubit evolves, all that can change are the > probability amplitudes of its TWO components. Am I mistaken? AG * > What would you say of qubit 5 in the above scenario, when it could be used to represent any of 1,000 possible results out of the 1,000,000 total combinations it can represent together with its 19 brothers? > > >> >>> >>>> If one denies the existence of the wave function >>>> >>> >>> >>> *I don't. AG * >>> >> >> Okay. That's good. If one accepts that the wave function is real, and >> that it can implement computations, >> > > *How can a wf implement computations"? AFAIK, when expanded into > orthogonal eigenstates, it can be use to calculate probabilities of each > eigenvalue corresponding to each eigenvalue. I never heard it could do more > than that. AG * > > You seem to be treating the wave function as a description of something that isn't really real, rather than a description of something that is real. But if it is not something that is really real, what ensures that only the 1,000 possible valid answers are produced, and not any of the 999,000 possible invalid answers? Jason -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
