RAISE-TAQS: Photon-Number-Resolving Integrated Avalanche Photodiodes for Scalable Quantum Computing

非技术性说明：量子计算和量子通信是从根本上利用量子力学特性来处理和交换信息的新兴领域。它们为各种应用提供了变革性的潜力，从比传统数字计算机更快地解决重要类别的问题，例如整数分解和模拟复杂的量子力学系统，到创建无法被黑客攻击的安全通信信道。任何使用光的量子计算机或量子通信网络都必须具有计算光子数量的能力，以纠正计算或传输错误;具体而言，需要接收器检测光子并将其转换为电信号，该电信号与在任何给定时刻到达接收器的光子的确切数量成比例。该项目旨在展示这样的接收器，并利用这种能力来执行对未来量子计算和量子通信系统具有基础科学和实际重要性的测量。这项研究在多个学科中产生了强烈的共鸣，从基础材料科学到基础物理学，再到工程学。它为研究生，本科生和高中生提供了独特的跨学科研究机会。一个关键的教育目标是让学生为他们可能面临的跨学科挑战做好准备，因为量子技术与工程交叉，同时在UT-奥斯汀和UVA提供广泛访问的，独立的“量子工程”课程，所有课程材料和录制的讲座免费提供给公众。该项目还将研究与外展活动相结合，例如通过课堂参观、公开讲座和与当地博物馆合作展览/图尔斯参观来激励K-12前的学生。技术描述：量子光子学是一种关键的量子技术。量子光子学的一个关键元件是光子数分辨光电探测器，它产生与入射光子数成比例的信号，从而能够完全获得量子电磁场的微粒性质。后者是量子信息中高光子通量应用的关键，例如量子通信中的量子中继器，纠缠蒸馏，量子纠错和使用压缩态的连续变量的容错通用量子计算。许多器件技术提供光子数分辨率，但通常在降低的温度下操作，通常需要大型冷却装置和大型阵列以实现适度的数分辨率。该项目研究了一种新的方法来应对这一挑战，其中单光子雪崩光电二极管（SPAD）被分解为几个波导耦合的“nanoSPAD”段，每个段通过单独的读出最多检测一个光子。目标是在室温下实现光子数分辨率，并有可能在高带宽下覆盖从可见光到中红外的波长-这是一个必不可少的组合，但任何现有技术都无法实现。通过基于全量子模型的设计，并通过新型低噪声III-V雪崩光电探测器材料实现，这种结构提供了具有高正算子值测量纯度的光子数分辨率的潜力。nanoSPAD单片集成到InP上，InP是现代长途电信的平台。光子数分辨nanoSPAD的能力的试金石测试是量子态层析成像和Fock态滤波的真实的时间演示。量子层析成像协议，反过来，用于表征光子数分辨率。nanoSPAD不仅能够实现量子断层扫描实验，还有望加速量子光子学领域的新科学突破。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical description: Quantum computing and quantum communications are emerging fields that harness fundamentally quantum mechanical properties to process and exchange information. They offer transformative potential for applications ranging from solving important classes of problems faster than traditional digital computers, such as integer factorization and simulating complex quantum mechanical systems, to creating secure communications channels that cannot be hacked. Any quantum computer or quantum communication network that uses light must have the ability to count the number of photons in order to correct computation or transmission errors; specifically, a receiver is required to detect and transduce the photons into an electrical signal that is proportional to the exact number of photons that reaches the receiver at any given moment. This project aims to demonstrate such a receiver and harnesses this capability to perform measurements that are of both fundamental scientific and practical importance for future quantum computing and quantum communications systems. This research resonates strongly across several disciplines, ranging from fundamental materials science, to basic physics, through engineering. It provides unique interdisciplinary research opportunities for graduate, undergraduate, and high school students. A key educational goal is to prepare students for the cross-disciplinary challenges they may face as quantum technology intersects engineering via a broadly accessible, self-contained course in "quantum engineering" simultaneously at UT-Austin and UVA, with all course materials and recorded lectures freely available to the general public. The project also integrates research with outreach activities, such as inspiring pre-K-12 students through classroom visits, public lectures, and collaborative exhibits/tours with local museums.Technical description: Quantum photonics is a key quantum technology. A critical element for quantum photonics is the photon-number-resolving photodetector, which produces a signal proportional to the number of incident photons, enabling full access to the corpuscular nature of quantum electromagnetic fields. The latter is key to high photon flux applications in quantum information, such as quantum repeaters in quantum communication, entanglement distillation, quantum error correction, and fault tolerant universal quantum computing over continuous variables using squeezed states. A number of device technologies offer photon number resolution, but typically operate at reduced temperatures, often requiring a large cooling apparatus and large arrays for modest number resolution. This project investigates a novel approach to this challenge, where a single photon avalanche photodiode (SPAD) is decomposed into several waveguide-coupled "nanoSPAD" segments, each detecting at most one photon via individual readout. The goal is photon number resolution at room temperature, with the potential to cover wavelengths from the visible to mid-infrared at high bandwidths - a combination that is essential, yet inaccessible with any existing technology. With design grounded in a fully quantum model and enabled by a new class of low noise III-V avalanche photodetector materials, this structure offers the potential for photon number resolution with high positive-operator-valued measurement purity. The nanoSPADs are integrated monolithically onto InP, the platform of modern long-haul telecommunications. The litmus test of the capabilities of the photon number resolving nanoSPAD is the demonstration of quantum state tomography and Fock-state filtering in real time. The quantum tomography protocol is, in turn, used to characterize the photon number resolution. Beyond enabling these quantum tomography experiments, it is expected that the nanoSPAD will accelerate new scientific breakthroughs in quantum photonics.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.