  This paper presents LEQA, a fast latency estimation tool for evaluating the
performance of a quantum algorithm mapped to a quantum fabric. The actual
quantum algorithm latency can be computed by performing detailed scheduling,
placement and routing of the quantum instructions and qubits in a quantum
operation dependency graph on a quantum circuit fabric. This is, however, a
very expensive proposition that requires large amounts of processing time.
Instead, LEQA, which is based on computing the neighborhood population counts
of qubits, can produce estimates of the circuit latency with good accuracy
(i.e., an average of less than 3% error) with up to two orders of magnitude
speedup for mid-size benchmarks. This speedup is expected to increase
superlinearly as a function of circuit size (operation count).
