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Quantum Computing: QuBit state from a multi-QuBit register (page 99)

DoLed

DoLed

Quantum Computing: QuBit state from a multi-QuBit register (page 99)

the statement “The quantum state of a qubit is obtained by reading across a row … |0011>” seems quite problematic to me.
First, the quantum (pure) state of the considered qubit is a priori not well defined any more at this stage, the global state of the 7-qubits register must be considered as a whole because of entanglement (see next chapter)
Second, even if we could assign this qubit a well defined quantum state, using the notation “0011>” for it is very misleading, as this is used also for the tensor product of qubit states…

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First Post!

nihal.mehta

nihal.mehta

Author of Quantum Computing

Hi Dominique,
All that the statement you referenced is saying is that the quantum state of the first qubit, q[0], is in a superposition of 4 states: |0>, |0>, |1>, |1>. This is simply abbreviated for ease of reading to |0011>.

You are right that that the entire state must be considered as a whole. This is precisely the mega-qubit.

Hope this helps.

Regards,
Nihal

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