Quantum entanglement is important for emerging quantum technologies such as quantum computation and secure quantum networks. To boost these technologies, a race is currently ongoing to increase the number of particles in multiparticle entangled states, such as Greenberger–Horne–Zeilinger (GHZ) states. An alternative route is to increase the number of entangled quantum levels. Here, we overcome present experimental and technological challenges to create a three-particle GHZ state entangled in three levels for every particle. The resulting qutrit-entangled states are able to carry more information than entangled states of qubits. Our method, inspired by the computer algorithm Melvin, relies on a new multi-port that coherently manipulates several photons simultaneously in higher dimensions. The realization required us to develop a new high-brightness four-photon source entangled in orbital angular momentum. Our results allow qualitatively new refutations of local-realistic world views. We also expect that they will open up pathways for a further boost to quantum technologies.

量子纠缠对于新兴的量子技术（例如量子计算和安全量子网络）非常重要。为了促进这些技术的发展，目前正在争相增加多粒子纠缠态（例如Greenberger–Horne–Zeilinger（GHZ）状态）中的粒子数量。另一种方法是增加纠缠的量子能级的数量。在这里，我们克服了当前的实验和技术挑战，以为每个粒子创建三个层次纠缠的三粒子GHZ状态。所产生的纠缠态比纠缠态能携带更多的信息。受计算机算法Melvin启发，我们的方法依赖于一个新的多端口，该端口可以在更高维度上同时相干地同时操纵多个光子。这一认识要求我们开发一种新的纠缠在轨道角动量中的高亮度四光子源。我们的结果允许对当地现实世界观进行质性上的新反驳。我们还期望它们将为进一步发展量子技术开辟道路。