1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: C: Modelling errors in a measurement

  1. Jun 6, 2013 #1
    1. The problem statement, all variables and given/known data
    I'm currently writing a program that will read in a list of gaussian distributed random numbers as an array and will make a 'measurement', that is they will be assigned to another array with an associated error. This is to try and simulate the communication of Alice to Bob in a continuous variable quantum key distribution protocol.

    In such a protocol there will be gaussian noise and therefore Bob will not receive the exact signal that was sent. For example, if there was a 50% spread around Alice's value that Bob could measure, how would I go about doing this?

    2. The attempt at a solution


    double a = (rand() % 100) - 50; //Produces a random number between -50 and 50
    bob = alice + (a/10); //Bob makes a measurement with a random error between -0.5 and 0.5

    fprintf(gaussBob, "%.4lg %.4lg\n",alice,bob);

    To me what I've done doesn't seem correct as there is just an addition of a random value between the specified range. Any help is appreciated.
  2. jcsd
  3. Jun 6, 2013 #2


    User Avatar
    2017 Award

    Staff: Mentor

    50% spread is a relative error? Or something absolute?
    I guess this should be a/100.
    This gives a uniform distribution, To get a Gaussian there are many algorithms.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted