- #1

EightBells

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- Homework Statement
- The quantum processor will provide information about the final state of

the system by performing projective measurement |1><1|. What are possible outcomes of

this measurement and what are the probabilities for this outcomes for each state listed

in Eq. (2). Explain, how you can perform projective measurements for states |±x> and

|±y> using the processor equipped with the standard single qubit gates and the projective

measurements |1><1|.

- Relevant Equations
- Eq. 2 gives the six states: |0>, |1>, |±x>=(1/sqrt(2))*(|0>±|1>), |±y>=(1/sqrt(2))*(|0>±i*|1>)

Am I correct in thinking that the system measures the probability |<f|1>|^2 for some state <f|? Then the probabilities for each of the six states would be:

|<0|1>|^2= 0

|<1|1>|^2= 1

|<+x|1>|^2= |(1/√2)|^2 = 1/2

|<-x|1>|^2= |(-1/√2)|^2 = 1/2

|<+y|1>|^2= |(-i/√2)|^2 = 1/2

|<-y|1>|^2= |(i/√2)|^2 = 1/2

However, what, specifically, is the question asking for when it asks for the possible outcomes of the measurements?

Performing projective measurements in|±x> and|±y>, am I looking for the probabilities |<f|±x>|^2 and |<f|±y>|^2, but in terms of state |1> which is done using the qubit gates? I know ZH|1> = |+x>, H|1> = |-x>, and SH|1> = |-y>, but I can't find a gate or series of gates that transforms |1> to |+y>, and I'm not sure how to use this to calculate the probabilities |<f|±x>|^2 and |<f|±y>|^2.

|<0|1>|^2= 0

|<1|1>|^2= 1

|<+x|1>|^2= |(1/√2)|^2 = 1/2

|<-x|1>|^2= |(-1/√2)|^2 = 1/2

|<+y|1>|^2= |(-i/√2)|^2 = 1/2

|<-y|1>|^2= |(i/√2)|^2 = 1/2

However, what, specifically, is the question asking for when it asks for the possible outcomes of the measurements?

Performing projective measurements in|±x> and|±y>, am I looking for the probabilities |<f|±x>|^2 and |<f|±y>|^2, but in terms of state |1> which is done using the qubit gates? I know ZH|1> = |+x>, H|1> = |-x>, and SH|1> = |-y>, but I can't find a gate or series of gates that transforms |1> to |+y>, and I'm not sure how to use this to calculate the probabilities |<f|±x>|^2 and |<f|±y>|^2.