The probability is a number between 0 and 1, so by definition it cannot be 2^30.
However, I think you were close.
First of all: I assume you want to know the probability that, in a heterozygous individual, sequencing 30 reads, you always sequence allele 1 and never allele 2.
Each read has a 0.5 probability of sequencing allele 1, and 0.5 of sequencing allele 2. The probability that with 2 reads you always sequence allele 1 is 0.5 * 0.5 (0.5^2), with 3 is 0.5^3, and so on… thus the probability that with 30 reads you always sequence allele 1 is 0.5^30, i.e. 9^-10.