  Semiquantitative group testing (SQGT) is a pooling method in which the test
outcomes represent bounded intervals for the number of defectives.
Alternatively, it may be viewed as an adder channel with quantized outputs.
SQGT represents a natural choice for Covid-19 group testing as it allows for a
straightforward interpretation of the cycle threshold values produced by
polymerase chain reactions (PCR). Prior work on SQGT did not address the need
for adaptive testing with a small number of rounds as required in practice. We
propose conceptually simple methods for 2-round and nonadaptive SQGT that
significantly improve upon existing schemes by using ideas on nonbinary
measurement matrices based on expander graphs and list-disjunct matrices.
