Mode-locked laser for spectrally multiplexed and network-compatible quantum memories

加拿大的经济、政治和社会福祉在很大程度上取决于安全的电子通信，例如电子银行、电子保健、电子商务和电子政务。然而，目前的公钥密码系统依赖于对计算复杂性的未经证实的假设，容易受到算法进步和更好的经典计算机技术的影响，并且随着量子计算机的出现而过时。因此，过去或现在编码和发送的信息的保密性，即使在今天仍然得到保证，也很容易受到未来密码破译技术的改进的影响，这可能导致在保护不足的情况下对记录的信息进行解码，然后它们就失去了重要性。量子密钥分发（QKD）利用在特定量子状态下制备的单个光子作为信息载体，有望最终解决这些问题：新技术无法破坏的安全性。然而，由于光子在传输过程中会丢失，而且由于量子力学的一个基本限制——不可克隆定理，放大器无法使用，量子密钥分配目前面临着200公里左右的距离限制。有趣的是，这一限制可以通过尚不存在的量子中继器来消除，这将在未来将量子计算机或原子钟连接到量子网络中发挥重要作用。这笔拨款将允许购买锁模皮秒激光器，这是初始化低温冷却稀土离子掺杂晶体所需的，用于存储在许多光谱通道中编码为大量光子的量子态。这些所谓的量子存储器构成了量子中继器和量子网络的关键成分，迫切需要改进。激光将消除目前影响进一步发展的一个重要瓶颈，即将频谱复用从经典（电信）世界转化为量子通信的问题。如果及时获得，它将实现我们在北美大陆上可靠的安全通信的长期目标。除了在各个职业层面培养高素质的人才和推进量子光学和量子通信领域之外，我们的研究，通过获得这种激光器，将确保加拿大在过去十年中对量子通信进行了大量投资后，在这一重要领域保持竞争力。

The economic, political, and social well-being of Canada depends crucially on secure electronic communications, e.g. for e-banking, e-health, e-commerce, and e-government. Yet, current public key cryptosystem rely on unproven assumptions about computational complexity, are susceptible to algorithmic advances and better classical computer technology, and will become obsolete with the advent of the quantum computer. Hence, the secrecy of messages encoded and sent in the past or present, even if still ensured today, is vulnerable to future improvements in code breaking, which may lead to decoding of recorded messages with insufficient protection before they lose importance. Quantum key distribution (QKD), which employs individual photons prepared in specific quantum states as carriers of information, promises the ultimate solution to these problems: security that cannot be compromised by new technology. Yet, as photons get lost during transmission and amplifiers cannot be used due to a fundamental restriction of quantum mechanics known as the no-cloning theorem, QKD currently faces a distance limit of around 200 km. Interestingly, this limit can be removed through not-yet-existing quantum repeaters, which will furthermore play an important role in future to connect quantum computers or atomic clocks into quantum networks. This grant will allow purchasing a mode-locked, picosecond laser, which is required to initialize cryogenically-cooled rare-earth-ion doped crystals for the storage of quantum states encoded into a large number of photons in many spectral channels. These so-called quantum memories form key ingredients of quantum repeaters and networks, and need urgent improvement. The laser will remove an important bottleneck that currently impacts further developments, i.e. the problem of translating spectral multipleximg from the classical (telecommunication) world into quantum communications. If acquired timely, it will seed our long-term aim of provable secure communication across the North American continent. In addition to creating highly qualified personnel at various career levels and advancing the fields of quantum optics and quantum communication, our research, through the acquisition of this laser, will ensure that Canada, after a lot of investment into quantum communication during the past decade, remains competitive in this important area.