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LookAheadDKRSAddLE operation

  • Article

Fully qualified name: Microsoft.Quantum.Unstable.Arithmetic.LookAheadDKRSAddLE

operation LookAheadDKRSAddLE(xs : Qubit[], ys : Qubit[], zs : Qubit[]) : Unit is Adj

Summary

Sets a zero-initialized little-endian register zs to the sum of little-endian registers xs and ys using the carry-lookahead algorithm.

Description

Computes zs := xs + ys + zs[0] modulo 2ⁿ, where xs, ys, and zs are little-endian registers, Length(xs) = Length(ys) ≤ Length(zs) = n, assuming zs is 0-initialized, except for maybe zs[0], which can be in |0> or |1> state and can be used as carry-in. NOTE: zs[Length(xs)] can be used as carry-out, if zs is longer than xs. This operation uses the carry-lookahead algorithm.

Reference

  • arXiv:quant-ph/0406142 "A logarithmic-depth quantum carry-lookahead adder", Thomas G. Draper, Samuel A. Kutin, Eric M. Rains, Krysta M. Svore