Sci.Physics.Foundations

FrediFizzx wrote: ↑Fri Sep 27, 2024 1:59 pm Measurement time.

That is just one time at which the qubit state Psi(t) is measured. Not two different times. So up and down states do exist at the same time, just as I said.

The spin system is in the qubit state, which is given by Psi(t) = a(t) x up + b(t) x down. This state Psi(t) is measured at the time of measurement, say t_m.
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Joy Christian wrote: ↑Sat Sep 28, 2024 12:22 am

FrediFizzx wrote: ↑Fri Sep 27, 2024 1:59 pm Measurement time.

That is just one time at which the qubit state Psi(t) is measured. Not two different times. So up and down states do exist at the same time, just as I said.

The spin system is in the qubit state, which is given by Psi(t) = a(t) x up + b(t) x down. This state Psi(t) is measured at the time of measurement, say t_m.

Measurement of the qubit produces an up OR down; not both.
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FrediFizzx wrote: ↑Sat Sep 28, 2024 10:16 am

Joy Christian wrote: ↑Sat Sep 28, 2024 12:22 am

FrediFizzx wrote: ↑Fri Sep 27, 2024 1:59 pm Measurement time.

That is just one time at which the qubit state Psi(t) is measured. Not two different times. So up and down states do exist at the same time, just as I said.

The spin system is in the qubit state, which is given by Psi(t) = a(t) x up + b(t) x down. This state Psi(t) is measured at the time of measurement, say t_m.

Measurement of the qubit produces an up OR down; not both.

And that transforms the qubit into an ordinary bit --- up-bit or down-bit --- which is useless for quantum computing, reducing it to classical computing.

In a qubit, Psi(t) = a(t) x up + b(t) x down, the spin exists in the up and down state at the same time. That is what is required for quantum computing.

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You seem to like Copilot and may believe it more than you believe me, so here is how it answered by question "What is a bit in QC?":

Copilot:

In quantum computing (QC), a bit can refer to either a classical bit or a quantum bit (qubit). Here’s a brief overview:

1. Classical Bit (cbit): This is the basic unit of classical information, which can be either 0 or 1.

2. Quantum Bit (qubit): This is the fundamental unit of quantum information. Unlike classical bits, qubits can exist in a superposition of states, meaning they can be both 0 and 1 simultaneously until measured.

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If this was not the case, why would anyone bother with qubits? Just work with up-bit OR down-bit, post-measurement, as you seem to think what QM is.
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Sure, mathematical artifacts can exist at the same time. Qubits give you 2^n mathematical artifact "states".
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FrediFizzx wrote: ↑Sun Sep 29, 2024 9:58 am Sure, mathematical artifacts can exist at the same time. Qubits give you 2^n mathematical artifact "states".

That is exactly the point Mikhail Dyakonov is making. For that reason, there will never be a quantum computer --- which is the theme of this thread.
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