Problem 3: Two-level system and density matrice Suppose a 2 x 2 matrix X (not necessarily Hermitian or unitary) is written as X = aooo + a.o, where ao and ak, k = 1, 2, 3, are numbers, 0 = 1 is the identity matrix and o are the Pauli matrices. (a) (b) How are ao and a related to tr(X) and tr(okX)? Obtain ao and a in terms of the matrix elements Xij.

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Problem 3: Two-level system and density matrice
Suppose a 2 x 2 matrix X (not necessarily Hermitian or unitary) is written as
X = a000 + a.σ,
where ao and ak, k = 1, 2, 3, are numbers, 0o = 1 is the identity matrix and o are the
Pauli matrices.
(a)
How are ao and a related to tr(X) and tr(OX)?
Obtain ao and ak in terms of the matrix elements Xij.
Assume that ao, ak ER such that X is Hermitian and could be
interpreted as a Hamiltonian, what are the eigenvalues of X?
Transcribed Image Text:Problem 3: Two-level system and density matrice Suppose a 2 x 2 matrix X (not necessarily Hermitian or unitary) is written as X = a000 + a.σ, where ao and ak, k = 1, 2, 3, are numbers, 0o = 1 is the identity matrix and o are the Pauli matrices. (a) How are ao and a related to tr(X) and tr(OX)? Obtain ao and ak in terms of the matrix elements Xij. Assume that ao, ak ER such that X is Hermitian and could be interpreted as a Hamiltonian, what are the eigenvalues of X?
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