Heralded photonic graph states with inefficient quantum emitters

TL;DR

This paper introduces a heralded method for creating photonic graph states using quantum emitters with poor photon collection efficiency, enabling scalable quantum computation and communication with polynomial overhead.

Contribution

The authors propose a heralded scheme compatible with inefficient quantum emitters, reducing construction time from exponential to polynomial in collection efficiency, and demonstrate its application in secure two-party computation.

Findings

Construction time scales polynomially with collection efficiency.

The scheme is compatible with current quantum emitter technology.

It enables efficient secure two-party quantum computation.

Abstract

Quantum emitter-based schemes for the generation of photonic graph states offer a promising, resource efficient methodology for realizing distributed quantum computation and communication protocols on near-term hardware. We present a heralded scheme for making photonic graph states that is compatible with the typically poor photon collection from state-of-the-art coherent quantum emitters. We demonstrate that the construction time for large graph states can be polynomial in the photon collection efficiency, as compared to the exponential scaling of current emitter-based schemes, which assume deterministic photon collection. The additional overhead here consists of an extra spin qubit plus one additional spin-spin entangling gate per photon added to the graph. While the proposed scheme requires both non-demolition measurement and efficient storage of photons in order to generate graph states for arbitrary applications, we show that many useful tasks, including measurement-based quantum computation, can be implemented without these requirements. As a use-case of our scheme, we construct a protocol for secure two-party computation that can be implemented efficiently on current hardware. Estimates of the fidelity to produce graph states used in the computation are given assuming current and near-term fidelities for highly coherent quantum emitters.