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

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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.