标题： 基于腔的量子网络中使用频率编码光子减轻双折射效应 显示英文标题

标题： Mitigation of birefringence in cavity-based quantum networks using frequency-encoded photons

摘要： 原子-腔系统通过提供强原子-光子耦合，同时允许对原子量子比特进行高保真局部操作，为构建大规模分布式量子计算机提供了独特优势。 然而，在常见的方案中，光子状态被编码在偏振态中，腔的双折射效应会引起腔本征模式的能量分裂，并改变偏振态，从而限制远程纠缠生成的保真度。 为解决这一挑战，我们提出了一种将光子量子比特编码在频率自由度上的方案。 该方案依赖于多个横向腔模与在频率上分离良好的不同原子跃迁之间的共振耦合。 我们在各种腔偏振模分裂情况下，数值研究了光子波包的时间特性、双光子干涉可见度以及原子-原子纠缠保真度，并发现我们的方案受腔双折射的影响较小。 最后，我们提出了两种被捕获离子系统的实际实现方案，分别利用了 $\mathrm{^{40}Ca^{+}}$的亚稳态 D 态中的精细结构分裂，以及 $\mathrm{^{225}Ra^{+}}$基态中的超精细分裂。 我们的研究提出了一种基于腔的量子网络的替代方法，该方法对双折射效应不敏感，并适用于多种原子和固态发射器-腔接口。 显示英文摘要

摘要： Atom-cavity systems offer unique advantages for building large-scale distributed quantum computers by providing strong atom-photon coupling while allowing for high-fidelity local operations of atomic qubits. However, in prevalent schemes where the photonic state is encoded in polarization, cavity birefringence introduces an energy splitting of the cavity eigenmodes and alters the polarization states, thus limiting the fidelity of remote entanglement generation. To address this challenge, we propose a scheme that encodes the photonic qubit in the frequency degree-of-freedom. The scheme relies on resonant coupling of multiple transverse cavity modes to different atomic transitions that are well-separated in frequency. We numerically investigate the temporal properties of the photonic wavepacket, two-photon interference visibility, and atom-atom entanglement fidelity under various cavity polarization-mode splittings and find that our scheme is less affected by cavity birefringence. Finally, we propose practical implementations in two trapped ion systems, using the fine structure splitting in the metastable D state of $\mathrm{^{40}Ca^{+}}$, and the hyperfine splitting in the ground state of $\mathrm{^{225}Ra^{+}}$. Our study presents an alternative approach for cavity-based quantum networks that is less sensitive to birefringent effects, and is applicable to a variety of atomic and solid-state emitter-cavity interfaces.