Reference no: EM131290822
Problem 1:
(a) A system is known to be in one of three states. Its probability of being in the first is 1/2 and of being in the second is 1/3. What is the density matrix for the system?
(b) Which, if any, of the following density matrices describe pure states?
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Problem 2: The state of a certain system is described by the density matrix
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(a) x ? , y = ?
(b) Verify whether or not the system is in a pure state.
Problem 3
(a) A system is known to be in one of two states. Show that the most general possible density matrix has the form
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(b) Show that β = ±√(α(1 - α) if the system is in a pure state.
(c) Show that α = 1/2, β = 0 for an unpolarized beam of particles of spin one-half.
(d) Find α and β (in a representation in which σz is diagonal) for a partially polarized beam of particles such that spin parallel to the z-axis occurs twice as often as spin anti-parallel to the z-axis.
Problem 4 The state of polarization of a beam of spin one-half particles is described by the polarization vector P defined in terms of the density matrix p as follows:
P = (σ) =Tr (ρσ).
Supposing P to be determined experimentally, show that
ρ = 1/2 (1 + P.σ).