  We present a novel and efficient in terms of circuit depth design for Shor's
quantum factorization algorithm. The circuit effectively utilizes a diverse set
of adders based on the quantum Fourier transform (QFT) Draper's adders to build
more complex arithmetic blocks: quantum multiplier/accumulators by constants
and quantum dividers by constants. These arithmetic blocks are effectively
architected into a generic modular quantum multiplier which is the fundamental
block for modular exponentiation circuit, the most computational intensive part
of Shor's algorithm. The proposed modular exponentiation circuit has a depth of
about $2000n^{2}$ and requires $9n+2$ qubits, where $n$ is the number of bits
of the classical number to be factored. The total quantum cost of the proposed
design is $1600n^{3}$. The circuit depth can be further decreased by more than
three times if the approximate QFT implementation of each adder unit is
exploited.
