I'm running this program (essentially a two bit random number generator) on ibmqx2 in IBM Q Experience. The backend matters. Other machines give unexpected results, but the graph looks different for other backends. So far ibmqx2 has been a good choice because a) it produces results that are far from the expected outcome and b) it produces results that are consistent run over run.
OPENQASM 2.0;
include "qelib1.inc";
gate nG0 ( param ) q {
h q;
}
qreg q[2];
creg c[2];
h q[0];
h q[1];
measure q[0] -> c[0];
measure q[1] -> c[1];
I always get results with the following shape. Note that "11" is a full ten points higher than "10". That happens almost every run. Any idea what's going on?