Time-to-digital converter for time-resolved multi-photon coincidence measurements

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Entanglement is the physical property that marks the most striking deviation of the quantum from the classical world. From a fundamental point-of-view, the possibility to create and distribute entangled photons to distant locations is fascinating because it leads to verifiable contradictions between predictions based on local realistic theories and those based on quantum mechanics (such verifications are known as tests of a “Bell-inequality”). On the other hand, entangled photons are at the heart of quantum teleportation, quantum repeaters and quantum networks, which allow the provably-secure distribution of encryption keys using quantum key distribution (QKD) and ultimately quantum communication with and between future quantum computers. Such a network will ensure secure communications within and between government departments and for the health and banking industries, businesses and individuals; allow one to send a computational task to a distant quantum cloud computer without anybody - not even the computer itself - being able to learn the task; and result in truly mind-boggling computational performance, e.g. for rapidly finding ‘a needle in a haystack’ (e.g. a specific entry in an unsorted database), for machine learning (e.g. for analyzing big data), and for understanding chemical reaction dynamics (e.g. to create better pharmaceuticals and refined petroleum products). Our long-term goal is the creation of a Canada-wide quantum network. This grant will allow purchasing a time-to-digital converter (TDC) for highly time-resolved coincidence measurements of detection signals created by up to eight single-photon detectors. The TDC is urgently required for near-future experiments with multiple entangled photon pairs that line the path towards a quantum network. Its timely acquisition will remove an important bottleneck that currently impacts further developments in the Tittel group: a limit in the maximum photon detection rate that our current TDCs can deal with; as well as the problem that our current devices start to deteriorate and may soon become dysfunctional. 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 TDC, will ensure that Canada, after a lot of investment into quantum communication during the past decade, remains competitive in this important area.