Time Propagation: Evaluating "exp(-i*H*t)

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SUMMARY

The discussion centers on the evaluation of the expression exp(-i*H*t) where H is a 2x2 zero matrix. The correct evaluation of this expression is established as the identity matrix, exp(0) = I, which equals [[1, 0], [0, 1]]. The user initially assumed the result would be [[1, 1], [1, 1]], which is incorrect. The mathematical definition of the matrix exponential confirms that the exponential of a zero matrix yields the identity matrix.

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I'm running a simple limiting case of a simulation with the expression:

exp(-i*H*t), where H is the hamiltonian, in this case a 2x2 matrix of zeros. Should this evaluate to 0, or to [ 1 1 ; 1 1] ?

Right now my sim uses the latter, which I'm sure is wrong. What do you think? Thanks in advance.
 
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By definition
[tex]\exp(A) = 1 + A + \frac{1}{2} A^2 + \frac{1}{6} A^3 + \cdots[/tex]

So exp(0) = 1
with 1 the identity matrix [tex]\begin{pmatrix}1&0\\0&1\end{pmatrix}[/tex].
 

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