Methods for linear optical quantum Fredkin gate

TL;DR

This paper proposes new linear optical methods for implementing a quantum Fredkin gate using heralded and post-selected schemes, potentially feasible with current technology, and explores different configurations including time entanglement.

Contribution

It introduces simplified linear optical schemes for the quantum Fredkin gate, reducing the number of required CNOT gates and eliminating the need for ancillary photons in some cases.

Findings

Heralded Fredkin gate constructed with four CNOT gates.

Simplified post-selected scheme using only two CNOT gates.

Feasible implementation with current experimental technology.

Abstract

We consider the realization of quantum Fredkin gate with only linear optics and single photons. First we construct a heralded Fredkin gate using four heralded controlled-not (CNOT) gates. Then we simplify this method to a post-selected one utilizing only two CNOT gates. We also give a possible realization of this method which is feasible with current experimental technology. Another post-selected scheme requires time entanglement of the input photons but needs no ancillary photons.