High-density time encoding of entangled photons for ultrafast telecom-compatible quantum secure communication

向超级量子计算机的快速发展将用于银行、国家安全和个人在线身份等方面的经典加密技术置于危险之中。量子密码学为牢不可破的安全提供了一种面向未来的解决方案。然而，较低的量子密钥传输速率以及缺乏电信友好的、紧凑的、可大规模生产的纠缠光子源，是与设备无关的安全协议所需的，阻碍了这一领域的进一步发展。 在这里，我们研究多能级(即量子双折射)时间绑定纠缠，以受益于其独特的潜力，将量子保密通信和大容量信息处理提高到Gbit/S速率。时间模式确实被广泛认为是最容易获得和最健壮的光子自由度，对科学和工业社区都有重大影响，最近在大城市距离上以Mbit/S密钥速率演示的量子加密协议就证明了这一点。在这里，通过使用纠缠光子量子体源，我们将通过增加每个光子的信息容量，在更低的重复率下展示类似的性能。在此背景下，所要求的设备具有2个通道，模拟带宽20 GHz，定时抖动&lt；10ps的任意波形发生器(AWG)，用于密集间隔光子时间盒的相干和精确的量子态处理。我们将通过使用专门的片上光学器件来生成和处理这种具有可伸缩维度的量子数，然而，这种器件需要至少几十皮秒的操作速度来进行量子态操作。所要求的超快AWG将允许我们执行多能级时间轴预测，这对于纠缠验证至关重要，否则在创纪录的快速GHz调制速度下是不可能实现的。该仪器将使我们能够在短期内确认第一代可达4能级甚至8能级的时间绑定纠缠量子，并在长期内演示首次通过全光纤集成隐形传输4能级和8能级光子。这些目标的实现将极大地推动量子光子学的进步，并将为魁北克和加拿大创造知识产权，以提高下一代量子技术的市场潜力。我们的系统的目标是在以下方面超越其他光子平台：1)量子信息处理速度达到电信级别的Gbit/S；2)在更高的噪声稳健性下增强每光子的信息容量；3)通过使用芯片集成和电信兼容的组件来提高稳定性、可扩展性和可访问性。所要求的设备还将极大地提高PI和合作者正在进行的其他项目的影响，并有助于在神经形态光子学和超快信号处理等高影响力领域进行HQP培训。

The rapid thrive towards supreme quantum computers puts the classical encryption techniques, used for, e.g., banking, national security, and personal online identity, at risk. Quantum cryptography offers a future-proof solution towards unbreakable security. However, low quantum key transfer rates as well as the lack of telecom-friendly, compact, and mass-producible entangled photons sources, needed for device-independent secure protocols, hamper further advances in this field. Here, we investigate multilevel (i.e., qudit) time-bin entanglement to benefit from its unique potential to boost quantum secure communication and large-capacity information processing to Gbit/s rates. Time modes are indeed widely recognized as the most accessible and robust photon degree of freedom, with significant impact on both the scientific and the industrial communities, as witnessed by the recent demonstrations of quantum encryption protocols at Mbit/s key rates over metropolitan distances. Here, by using sources of entangled photon qudits, we will demonstrate similar performances at even lower repetition rates by increasing the information capacity per photon. In this context, the requested equipment an arbitrary waveform generator (AWG) with 2 channels, analog bandwidth > 20 GHz, and timing jitter < 10 ps, as used in telecom facilities will be adapted for coherent and precise quantum state processing of densely-spaced photon time bins. We will generate and process such qudits with scalable dimensionality by using specialized on-chip optical devices, which however require operational speeds of at least few tens of picosecond for quantum state manipulation. The requested ultrafast AWG will allow us to perform multilevel time-bin projections that are critical for entanglement verification and that would be otherwise impossible to accomplish at record-fast GHz modulation-speeds. The instrument will enable us to confirm, in a short term, the first on-chip generation of time-bin entangled qudits up to 4 and even 8 levels, as well as, in a longer term, to demonstrate first-time all-fiber-integrated teleportation of 4- and 8-level photons. The accomplishment of these objectives will critically boost advances in quantum photonics, as well as will create intellectual property for Quebec and Canada towards elevating market potential for next-generation quantum technologies. Our system aims to outperform other photonic platforms in terms of 1) quantum information processing rates towards telecom-level Gbit/s, 2) enhanced information capacity per photon at higher noise robustness, and 3) increased stability, scalability, and accessibility by using chip-integrated and telecom-compatible components. The requested equipment will also greatly elevate the impact of other active projects of the PI and collaborators, as well as contribute to HQP training in highly impactful fields such as neuromorphic photonics and ultrafast signal processing.