Integrated Optics as a Platform for Continuous Variable Measurement Based Quantum Computing

最近，已经有使用LiNbate和硅基集成芯片架构进行挤压的演示[5]。这些结果被认为对量子计算是有用的，然而到目前为止所实现的压缩水平很低。同样在最近，使用体光学[1，2]已经产生了极大的2D连续可变团簇状态。这些演示的一个关键因素是大的时间延迟，以实现时间绑定编码的使用。增加簇中输入模式的数量需要增加延迟，从而限制输入寄存器的可扩展性。该PHD旨在探索利用集成光学技术产生CV簇态，以期设计一个可扩展的集成平台。一个关键的实验挑战是协调簇态验证所需的压缩电平(~3-5dB)和完全容错(~15-17db[7])，目前的综合结果为~1-2db。因此，PHD的第一阶段将是使用商业上可获得的锂Nobite模块耦合到带有集成零差探测器的芯片中，以观察所需的最小3db的挤压。PHD具有足够的灵活性，可以在满足要求的情况下旋转和使用已演示的基于硅和氮化硅的挤压。一旦实现了这一点，PHD的里程碑将是理解、设计、构建和验证基于现有整体方案的一维集成海量团簇状态生成平台[3]。这个项目的延伸目标将是在集群状态上实现高斯运算，以演示遵循最近建立的技术的概念的计算证明[4]。第二个目标项目将是将集群状态扩展到2D。然而，由于双时间段编码方法所需的大延迟(和相关损失)，将需要探索使用频率和/或空间模式的替代平台[6]。PHD的这一子主题将构成项目的多种可能性，包括在两个光谱分离的频率模式之间执行态隐形传态，以及使用生成的实验来演示多方纠缠。最后，PHD的另一个方向将是研究在CV计算中容错所需的非高斯态的光学产生。除了实验项目，PHD还将包括与通用CV-MBQC的容错相关的重要理论组件。为了利用纠错技术，需要一个玻色码来在连续系统中嵌入一个量子比特。此外，为了实现通用性，需要非高斯运算。这两个挑战都可以通过使用注入到团簇状态的‘GKP’量子比特来解决[8]。建议与Nicolas Menicucci合作，通过研究混合高斯/GKP编码方案来直接解决其中一些挑战。拟议的合作将涉及在RMIT借调尼克的团队3-6个月来开发这个项目。二维团簇态https://science.sciencemag.org/content/366/6463/3692.的确定性产生产生时间域多路复用的二维团簇态https://science.sciencemag.org/content/366/6463/3733.无限时域复用https://aip.scitation.org/doi/10.1063/1.4962732[4].产生百万模连续变量团簇态4.时钟频率为25 MHz https://arxiv.org/pdf/2006.11537.pdf5.的百步量测量子计算在时间域中的多路复用纳米光子器件https://arxiv.org/abs/2001.094746.中双泵浦四波混频的单模正交压缩Https://arxiv.org/pdf/1912.112157.Https://journals.aps.org/pra/abstract/10.1103/PhysRevA.100.0103018.Https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.123.200502

Recently there have been demonstrations of squeezing using Lithium Niobate and Silicon-based integrated chip architectures[5]. These results have been claimed to be useful for quantum computing, however the squeezing levels achieved so far are low. Also recently, extremely large 2D continuous variable cluster states have been generated using bulk optics[1,2]. A key element of these demonstrations were large temporal delays to enable the use of time-bin encoding. Increasing the number of input modes in the cluster requires an increase in the delay, constraining the scalability of an input register. This PhD aims to explore the generation of CV cluster states using integrated optical technology with the view to designing a scalable integrated platform.A key experimental challenge to be addressed is the reconciliation of the squeezing levels required for cluster state verification (~3-5dB) and full fault tolerance (~15-17dB [7]) with current integrated results of ~1-2dB. A first stage of the PhD would therefore be to use commercially available lithium niobite modules coupled into a chip with integrated Homodyne detectors to observe the minimum 3dB of squeezing required. The PhD is sufficiently flexible to pivot and use demonstrated silicon and silicon-nitride based squeezing if they meet requirements.Once this has been achieved, a milestone of the PhD will be to understand the theory of, design, construct and verify a 1D integrated massive cluster state generation platform based upon existing bulk schemes[3]. A stretch goal of this project would then be to implement gaussian operations on the cluster state to demonstrate a computing proof of concept following recently established techniques[4]. A second targeted project will be to extend the cluster state to 2D. However, due to the large delays required (and associated losses) in the double time-bin encoding method an alternative platform using frequency and/or spatial modes will need to be explored[6]. This sub theme of the PhD will constitute multiple possibilities for projects, including performing state teleportation between two spectrally separate frequency modes and using the generated experiments for multi-partite entanglement demonstrations. Finally, an alternate direction for the PhD would be to look at optical generation of required non gaussian states for fault tolerance in CV computation.In addition to the experimental projects, the PhD will also consist of a significant theory component relating to Fault Tolerance for Universal CV-MBQC. To take advantage of error correction techniques, a bosonic code is needed to embed a qubit within the continuous system. Furthermore, to enable universality a Non-Gaussian operation is needed. Both of these challenges can be resolved by the use of 'GKP' qubits which are injected into the cluster states[8]. A collaborative effort with Nicolas Menicucci is proposed to directly address some of these challenges by studying mixed Gaussian / GKP encoding schemes. The proposed collaboration will involve a secondment at RMIT within Nick's group for 3-6 months to develop this project.1. Deterministic generation of a two-dimensional cluster state https://science.sciencemag.org/content/366/6463/3692. Generation of time-domain-multiplexed two-dimensional cluster state https://science.sciencemag.org/content/366/6463/3733. Generation of one-million- mode continuous-variable cluster state by unlimited time-domain multiplexing https://aip.scitation.org/doi/10.1063/1.4962732[4]. 4. One-hundred step measurement-based quantum computation multiplexed in the time domain with 25 MHz clock frequency https://arxiv.org/pdf/2006.11537.pdf5. Single-mode quadrature squeezing using dual-pump four-wave mixing in a nanophotonic device https://arxiv.org/abs/2001.094746. https://arxiv.org/pdf/1912.112157. https://journals.aps.org/pra/abstract/10.1103/PhysRevA.100.0103018. https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.123.200502