Efficient Fusion of Photonic W-states with Nonunitary Partial-swap Gates

TL;DR

This paper presents a novel nonunitary partial-swap gate for efficient, scalable fusion of small photonic W-states into larger entangled networks using linear optics, auxiliary degrees of freedom, and recyclable outcomes.

Contribution

It introduces a new nonunitary partial-swap gate that improves success probability and reduces complexity in fusing photonic W-states without ancillary photons.

Findings

Higher success probability with less resource cost

Simpler setup compared to previous methods

Recyclable 'garbage' states eliminate complete failure outputs

Abstract

We introduce a nonunitary partial-swap gate for fusing arbitrary small-sized photonic W-states into a large-scale entangled network of W-state efficiently without ancillary photons. A partial-swap gate is designed in an optical architecture based on linear optics elements. By introducing auxiliary degree of freedom, this gate provides a higher success probability with less cost. Our implementation can create a larger target state with a simpler set-up than previous proposals for W-state fusion. Also all "garbage" states are recyclable, i.e., there is no complete failure output in our scheme in principle.