# quantum physics

8(a) Consider a spin qubit in the state 3ã2|0⟩+12|1⟩. What are the coordinates (ƒÆ,ϕ) of this qubit on the Bloch sphere?
ƒÆ=?
ϕ=?

8b. We turn on a magnetic field in the z^ direction at time t=0. This corresponds to the Hamiltonian H=BZ, where B is a constant and Z is the usual phase flip. What is the state of our qubit at time t as a function of B and t?

8c. What are the coordinates (ƒÆ,ϕ) of this qubit on the Bloch sphere at time t, as a function of B and t?

8d. Now suppose we start with the qubit |ƒÕ(0)⟩=|0⟩ and we apply a magnetic field in the x^ direction at t=0. This corresponds to the Hamiltonian H=BX, where B is a constant and X is the usual bit flip gate. What are the coordinates (ƒÆ,ϕ) of this qubit on the Bloch sphere at time t, as a function of B and t?
ƒÆ=?
ϕ=?

posted by Anonymous
2. D
ƒÆ = 2Bt
phi = pi/2

C - pi/3; 2*B*t

do you need explanation ?

posted by david
3. @ David thanks but its wrong for d.

posted by Anonymous

posted by Anonymous
5. try ƒÆ = 2Bt
and phi = 0

posted by ss01
6. sorry for that
@ss01 your phi is wrong that i am for sure it cannot be 0

posted by david
7. got my error
8d ƒÆ= 0 and ϕ = 2bt
check and tell me if i am right?
8a ƒÆ = pi/3 and ϕ = 0

posted by david
8. r u right,david abt 8d?

posted by stuart
9. r u right,david abt 8d?and wat abt 8 b?

posted by stuart
10. ya, this time

posted by david
11. doing 8b

posted by david
12. its wrong.8 d,

posted by stuart

posted by Anonymous
14. 8b:
e^(-i*B*t)*sqrt(3)/2
e^(i*B*t)/2

posted by Anonymous
15. 8D
θ= 2⋅B⋅t
ϕ= 3⋅π/2

posted by Tu papi

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