Quantum Photonic Simulation of Molecular Spectra

项目概述：开发基于量子光干涉的分子振动光谱量子增强模拟器。光子处理能力目前远远不能满足通用量子计算的严格要求；然而，光子学确实为有限用途的处理器提供了独特而强大的方法。例如，玻色子采样（BS）计算问题，涉及到从多端口干涉仪出来的单光子的统计，被认为是一个有前途的框架，用于量子计算霸权的实验论证。我们在这里提出的项目建立在一个BS变异的基础上，该变异识别了与分子转变的联系，该变异最近由Alán Aspuru-Guzik （Harvard）及其合作者（10.1038/nphoton.2015.153）提出。在这个方案中，量子光的干涉自然地模拟了复杂分子中的电子-振动跃迁。这种干涉仪的统计数据将揭示分子的光谱——这是理论化学的一项关键任务，目前受到经典计算能力的限制。这个学生项目旨在实现这种类型的模拟器的第一次演示。我们还将发展模拟器与高斯玻色子采样的理论联系，澄清实验不精确的后果，并制定一条超越当前经典计算能力的分子模拟路线。该项目属于EPSRC量子技术研究领域，因为它是与NQIT中心相关的学生项目之一。这个项目的影响将包括它对NQIT目标的贡献：构建光子模拟器是NQIT交付的D23（第58个月）。在目前的计划中，这包括一个大型BS机器（基于“散射”变化）和一个用于DMFT计算的小型协处理器（与NQIT的量子模拟研究小组合作）。所提出的器件是光子模拟器的新概念。如果成功，该设备将把BS的计算前景与化学和分子生物学中广泛感兴趣的任务联系起来，其影响将超越量子霸权的学术竞赛。一位全职NQIT研究人员正在研究光子模拟器。到目前为止，这主要涉及通过与非nqit项目的研究人员合作开发模拟器的技术组件。拟议的项目与正在进行的工作密切相关，关键的是，它提供了一个专门的研究人员来研究这个有前途的新概念。分子模拟器是专用量子处理器的一个例子，它运行时不需要纠错。光子模拟器将在这种类型的计算中刺激NQIT活动，这可能是第一个在有趣的规模上实现NQIT离子阱处理器。NQIT研究人员需要研究的重要理论问题包括验证和容错。构建模拟器的技术要求与NQIT光子学其他方面开发和使用的光源、干涉仪和探测器完全重叠。除了NQIT，我们还将与Aspuru-Guzik合作，编写一套从计算化学家的角度来看很有趣的分子测试集，并了解如何通过光学损耗和减相来模拟现实环境（例如溶液中的碰撞）。

Project summary: We will develop a quantum-enhanced simulator of molecular vibronic spectra, based on the interference of quantum light. Photonic processing capabilities are currently far from meeting the stringent requirements for universal quantum computation; however, photonics does provide unique, and powerful, approaches to limited-purpose processors. For example, the Boson Sampling (BS) computing problem, which concerns the statistics of single photons exiting a multi-port interferometer, is recognized as a promising framework for the experimental demonstration of quantum supremacy in computing. The project we propose here builds on a BS variation that identifies a connection to molecular transitions, recently put forth by Alán Aspuru-Guzik (Harvard) and collaborators (10.1038/nphoton.2015.153). In this scheme, the interference of quantum light naturally emulates the electronic-vibronic transitions in complex molecules. The statistics from such an interferometer will reveal the spectrum of the molecule- a key task in theoretical chemistry that is currently limited by the power of classical computation. This student project aims to achieve the first demonstration of this type of simulator. We will also develop a theoretical connection of the simulator to Gaussian Boson Sampling, clarify the consequences of experimental imprecision, and formulate a route to molecule simulation that will surpass the current capacity of classical computation. This project falls within the EPSRC Quantum Technologies research area, as it is one of the studentship projects associated with the NQIT Hub. The impact of this project will include its contribution toward NQIT goals: building a photonic simulator is NQIT deliverable D23 (Month 58). In current plans, this consists of a large-scale BS machine (based on the "scattershot" variation) and a small-scale co-processor for DMFT calculation (with the quantum simulation research group in NQIT). The proposed device is a new concept for a photonic simulator. If successful, this device would have impact beyond the academic race to quantum supremacy by connecting the computational promise of BS to a task of wide interest in chemistry and molecular biology. One full-time NQIT researcher is working towards the photonic simulator. To date, this has primarily involved developing technical components for the simulator through collaborative projects with researchers working on non-NQIT projects. The proposed project aligns closely with this ongoing work, and critically, it provides a dedicated researcher needed to investigate this promising new concept. The molecular simulator is an example of a purpose-built quantum processor that runs without error correction. The photonic simulator will stimulate NQIT activity in this type of computation, which is likely to be the first achieved at an interesting scale with an NQIT ion-trap processor. Important theoretical problems to investigate with NQIT researchers include verification and error tolerance. The technical requirements to build the simulator have complete overlap with the light sources, interferometers, and detectors developed and used for other aspects of NQIT photonics. Beyond NQIT, we will collaborate with Aspuru-Guzik to compile a test set of molecules that are interesting from the perspective of a computational chemist, and understand how a realistic environment (e.g. collisions in solution) is simulated by optical loss and dephasing.