- #1
munirah
- 31
- 0
Homework Statement
Good day,
I want to ask the matrix that obtained from below formula and example.
$$tr_A(L_{AB})=\sum_i [(\langle i|\otimes id)L_{AB}(|i\rangle\otimes id)]$$
this formula above can be represented as in matrix form below,
$$tr_A(L_{AB})= \left(\array{1&0&0&0\\0&1&0&0}\right)\cdot \left(\array{0&0&1&0\\1&0&0&0\\0&0&0&0\\0&0&0&0} \right)\cdot \left( \array{1&0\\0&1\\0&0\\0&0}\right)=\left(\array{0&0\\1&0} \right)$$
My question are:
1.what its mean by d in this formula? How can I get this d?
2.How he get the first 2X4 matrix? I already calculate but I just get first row only. How it compute from the formula exactly?
Thank you