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『Quantum Computing: A Gentle Introduction』の演習問題を解く 3.12

Quantum Computing: A Gentle Introduction (Scientific and Engineering Computation) (English Edition)

Quantum Computing: A Gentle Introduction (Scientific and Engineering Computation) (English Edition)

目次はこちら

Exercise 3.12. Give an example of a two-qubit state that is a superposition with respect to the standard basis but that is not entangled.

  { \displaystyle\begin{align*}
  \frac{1}{2}\left(|00\rangle + |01\rangle + |10\rangle + |11\rangle\right)
    &= \frac{1}{\sqrt{2}}\left(|0\rangle_1 + |1\rangle_1\right) \otimes \frac{1}{\sqrt{2}}\left(|0\rangle_0 + |1\rangle_0\right)
\end{align*}}