Haplogroup Q-M323 is defined by the presence of the M323 Single Nucleotide Polymorphism (SNP).
Q-M323 was discovered in the Yemeni Jewish population.
[1] In the time since its discovery, it has not been detected in other populations.
It could then be exclusive to this population.
This is Thomas Krahn at the Genomic Research Center's Draft tree Proposed Tree for haplogroup Q-M323.