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Wednesday, April 8, 2015

Exploring Quantum Physics - Week 2 Question 2

Question:

The probability for particle to be at r2 at t2 if it was at r1 at t1 is given by |G(r2,t2;r1,t1)|2 . Let us consider a propagator between points r1  and r2  at time t_1 and t_2 which has the form G(r2,t2;r1,t1)=a+b, where a and b are complex and non-zero. This can, in some sense, be considered the case where there are two (and only two) possible ways for particle to travel from (r1,t1) to (r2,t2). What is the probability for the particle to go from (r1,t1) to (r2,t2) ?

Recall that the complex conjugate of a complex number z=x+iy is z=xiy, where x and y are real numbers.

Solution:

This is a really complicated way to simply asking what is |a+b|2, We can simply compute that as |a+b|2=(a+b)(a+b)=(a+b)(a+b)=aa+ab+ba+bb=|a|2+ab+ba+|b|2

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