Resource-efficient loss-aware photonic graph state preparation using atomic emitters

TL;DR

This paper introduces an algorithm for resource-efficient photonic graph state preparation using atomic emitters, optimizing the tradeoff between emitter number and graph depth to improve quantum communication rates.

Contribution

The paper presents a novel algorithm that reduces resource requirements for photonic graph state generation by balancing emitter count and circuit depth, outperforming existing methods.

Findings

Achieves superior rate-distance tradeoff in quantum repeaters

Uses five orders of magnitude fewer emitters than linear-optics methods

Minimizes emitter CNOT gates to reduce photon loss

Abstract

Multi-qubit entangled photonic graph states are an important ingredient for all-photonic quantum computing, repeaters and networking. Preparing them using probabilistic stitching of single photons using linear optics presents a formidable resource challenge due to multiplexing needs. Quantum emitters provide a viable solution to prepare photonic graph states as they enable deterministic production of photons entangled with emitter qubits, and deterministic two-qubit interactions among emitters. A handful of emitters often suffice to generate useful-size graph states that would otherwise require millions of emitters used as single photon sources, using the linear-optics method. Photon loss however impedes the emitter method due to a large circuit depth, and hence loss accrual on the photons of the graph state produced, given the typically large number of slow two-qubit CNOT gates between emitters. We propose an algorithm that can trade the number of emitters with the graph-state depth, while minimizing the number of emitter CNOTs. We apply our algorithm to generate a repeater graph state (RGS) for a new all-photonic repeater protocol, which achieves a far superior rate-distance tradeoff compared to using the least number of emitters needed to generate the RGS. Yet, it needs five orders of magnitude fewer emitters than the multiplexed linear-optics method -- with each emitter used as a photon source -- to achieve a desired rate-distance performance.