A chip-scale polarization-spatial-momentum quantum SWAP gate in silicon nanophotonics
A chip-scale polarization-spatial-momentum quantum SWAP gate in silicon nanophotonics
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DOI：
10.1038/s41566-023-01224-x
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发表时间：
2023-06-15
期刊：
影响因子：
35
通讯作者：
Wong, Chee Wei
中科院分区：
文献类型：
--
作者：
Cheng, Xiang;Chang, Kai-Chi;Wong, Chee Wei
在硅片上实现了一种确定性的偏振态和空间动量态之间的单光子双量子比特SWAP门。得到了94.9%的两量子比特交换过程保真度。通过双光子干涉验证了SWAP门过程的相干性。量子计算和网络的最新进展使得通过连接不同的量子模块来实现高性能、大规模的量子处理器成为可能。光量子系统在计算和通信方面都显示出优势，集成量子光子学进一步提高了规模和复杂性。在这里，我们展示了一个有效的SWAP门，确定性地交换光子的偏振量子位与它的空间动量量子位的纳米制造的两级硅光子芯片包含三个级联门。片上SWAP门的全面特征在于具有高保真度的单量子位和双量子位操作的层析测量。通过单光子和双光子量子干涉验证了SWAP门过程的相干保持性。我们的SWAP门的相干可逆转换有利于检查两个芯片级光子子系统之间的量子互连具有不同的自由度，现在通过在两个芯片之间分布四个贝尔状态来证明。我们还阐明了在SWAP操作中的退相干的来源，以追求接近统一的保真度。我们在硅平台上的确定性SWAP门为互连模块化系统的集成量子信息处理提供了一条途径。
A deterministic single-photon two-qubit SWAP gate between polarization and spatial-momentum is demonstrated on a silicon chip. A two-qubit swapping process fidelity of 94.9% is obtained. The coherence preservation of the SWAP gate process is verified by two-photon interference.Recent progress in quantum computing and networking has enabled high-performance, large-scale quantum processors by connecting different quantum modules. Optical quantum systems show advantages in both computing and communications, and integrated quantum photonics further increases the level of scaling and complexity. Here we demonstrate an efficient SWAP gate that deterministically swaps a photon's polarization qubit with its spatial-momentum qubit on a nanofabricated two-level silicon photonics chip containing three cascaded gates. The on-chip SWAP gate is comprehensively characterized by tomographic measurements with high fidelity for both single-qubit and two-qubit operation. The coherence preservation of the SWAP gate process is verified by single-photon and two-photon quantum interference. The coherent reversible conversion of our SWAP gate facilitates examinations of a quantum interconnect between two chip-scale photonic subsystems with different degrees of freedom, now demonstrated by distributing four Bell states between the two chips. We also elucidate the source of decoherence in the SWAP operation in pursuit of near-unity fidelity. Our deterministic SWAP gate in the silicon platform provides a pathway towards integrated quantum information processing for interconnected modular systems.