  Since Shor's proposition of the method for factoring products of prime
numbers using quantum computing, there has been a quest to implement efficient
quantum arithmetic algorithms. These algorithms are capable of applying
arithmetic operations simultaneously on large sets of values using quantum
parallelism. Draper proposed an addition algorithm based on the quantum Fourier
transform whose operands are two quantum registers, which I refer to as
register-by-register addition. However, for cases where there is the need to be
added a constant value to a target register, Draper's algorithm is more complex
than necessary in terms of number of operations and number of qubits used. In
this paper, I present a more efficient addition algorithm than Draper's for
cases where there needs to be added just a constant to a target register.
