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IncByLEUsingAddLE operation

  • Article

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

operation IncByLEUsingAddLE(forwardAdder : ((Qubit[], Qubit[], Qubit[]) => Unit is Adj), backwardAdder : ((Qubit[], Qubit[], Qubit[]) => Unit is Adj), xs : Qubit[], ys : Qubit[]) : Unit is Adj + Ctl

Summary

Generic operation to turn two out-place adders into one in-place adder

Description

This implementation allows to specify two distinct adders for forward and backward direction. The forward adder is always applied in its body variant, whereas the backward adder is always applied in its adjoint variant. Therefore, it's possible to, for example, use the ripple-carry out-of-place adder in backwards direction to require no T gates.

The controlled variant is also optimized in a way that everything but the adders is controlled,

Reference

  • arXiv:2012.01624 "Quantum block lookahead adders and the wait for magic states", Craig Gidney.