Prasad Rohit, Reiß Simon D, Peniakov Giora, Reum Yorick, van Loock Peter, Höfling Sven, Huber-Loyola Tobias, Pfenning Andreas Theo
Lehrstuhl für Technische Physik, Julius-Maximilians-Universität Würzburg, Physikalisches Institut, Am Hubland, 97074, Würzburg, Germany.
Institute of Physics, Johannes-Gutenberg University of Mainz, Staudingerweg 7, 55128, Mainz, Germany.
Nano Converg. 2025 Sep 19;12(1):44. doi: 10.1186/s40580-025-00510-4.
By precisely timed optical excitation of their spin, optical emitters such as semiconductor quantum dots or atoms can be harnessed as sources of linear photonic cluster states. This significantly reduces the required resource overhead to reach fault-tolerant optical quantum computing. Here, we develop an algorithm that analytically tracks the global density matrix through the process of the protocol for generating linear-cluster states by Lindner and Rudolph. From this we derive a model to calculate the entangling gate fidelity and the state fidelity of the generated linear optical cluster states. Our model factors in various sources of error, such as spin decoherence and the finite excited state lifetime. Additionally, we highlight the presence of partial reinitialization of spin coherence with each photon emission, eliminating the hard limitation of coherence time. Our framework provides valuable insight into the cost-to-improvement trade-offs for device design parameters as well as the identification of optimal working points. For a combined state-of-the-art quantum dot with a spin coherence time of ns and an excited state lifetime of ps, we show that a near-unity entangling gate fidelity as well as near-unity state fidelity for 3-photon and 7-photon linear cluster states can be reached.
通过对诸如半导体量子点或原子等光学发射器的自旋进行精确计时的光激发，可以将其用作线性光子簇态的源。这显著降低了实现容错光学量子计算所需的资源开销。在此，我们开发了一种算法，该算法通过Lindner和Rudolph生成线性簇态的协议过程来解析跟踪全局密度矩阵。由此，我们推导出一个模型，用于计算生成的线性光学簇态的纠缠门保真度和态保真度。我们的模型考虑了各种误差源，如自旋退相干和有限的激发态寿命。此外，我们强调了每次光子发射时自旋相干的部分重新初始化的存在，消除了相干时间的严格限制。我们的框架为器件设计参数的成本与改进权衡以及最佳工作点的识别提供了有价值的见解。对于一个自旋相干时间为纳秒且激发态寿命为皮秒的组合式先进量子点，我们表明对于3光子和7光子线性簇态可以实现接近单位的纠缠门保真度以及接近单位的态保真度。
