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Let
σ
y
=
[
0
−
i
i
0
]
\sigma_y = \begin{bmatrix}0 & -i \\ i & 0\end{bmatrix}
σ
y
=
[
0
i
−
i
0
]
. Compute the matrix product
σ
y
⋅
σ
y
\sigma_y \cdot \sigma_y
σ
y
⋅
σ
y
. What is the real part of its top-left (0,0) entry?
🔬 try it before you answer
-1
i
i
i
(imaginary, real part 0)
0
1
Check answer