Posted by **Anonymous** on Friday, October 18, 2013 at 2:06am.

8(a) Consider a spin qubit in the state 32|0⟩+12|1⟩. What are the coordinates (,ϕ) of this qubit on the Bloch sphere?

=?

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 (,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 |(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 (,ϕ) of this qubit on the Bloch sphere at time t, as a function of B and t?

=?

ϕ=?

- quantum physics -
**Anonymous**, Friday, October 18, 2013 at 2:07am
please help!!

- quantum physics -
**david**, Friday, October 18, 2013 at 2:28am
D

= 2Bt

phi = pi/2

C - pi/3; 2*B*t

do you need explanation ?

- quantum physics -
**Anonymous**, Friday, October 18, 2013 at 4:40am
@ David thanks but its wrong for d.

- quantum physics -
**Anonymous**, Friday, October 18, 2013 at 4:41am
can you explain..please

- quantum physics -
**ss01**, Friday, October 18, 2013 at 5:22am
try = 2Bt

and phi = 0

- quantum physics -
**david**, Friday, October 18, 2013 at 5:30am
sorry for that

@ss01 your phi is wrong that i am for sure it cannot be 0

- quantum physics -
**david**, Friday, October 18, 2013 at 5:35am
got my error

8d = 0 and ϕ = 2bt

check and tell me if i am right?

8a = pi/3 and ϕ = 0

- quantum physics -
**stuart**, Friday, October 18, 2013 at 5:45am
r u right,david abt 8d?

- quantum physics -
**stuart**, Friday, October 18, 2013 at 5:46am
r u right,david abt 8d?and wat abt 8 b?

- quantum physics -
**david**, Friday, October 18, 2013 at 5:46am
ya, this time

- quantum physics -
**david**, Friday, October 18, 2013 at 5:47am
doing 8b

- quantum physics -
**stuart**, Friday, October 18, 2013 at 5:51am
its wrong.8 d,

- quantum physics -
**Anonymous**, Friday, October 18, 2013 at 1:55pm
please help with 8d!!

- quantum physics -
**Anonymous**, Friday, October 18, 2013 at 2:32pm
8b:

e^(-i*B*t)*sqrt(3)/2

e^(i*B*t)/2

please help with Q8D please

- quantum physics -
**Tu papi**, Friday, October 18, 2013 at 11:53pm
8D

θ= 2⋅B⋅t

ϕ= 3⋅π/2

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