The CAPABLE project has achieved many important breakthroughs. In the following, I will describe the main ones.
A first important result is the demonstration of very efficient laser-written waveguides in Pr3+:Y2SiO5 crystals, which is one of the most promising material for solid-state quantum memories. Exploiting these waveguides, we have demonstrated a single-photon integrated quantum memory with orders of magnitude longer storage times than any previous waveguide implementation and 100x reduced amount of power needed for the control signals. These results enabled the storage of a total number of ~130 modes in a single waveguide and, more recently, the demonstration of entanglement-storage in fiber-coupled integrated quantum memories, towards the vision of a quantum internet.
On the quantum protocol side, we have addressed a relevant problem: how can one validate a quantum machine when its computational power will exceed that of a classical computer? We have considered the Boson Sampling algorithm, which is known to be extremely hard to compute classically, and we have experimentally demonstrated a new technique based on machine learning that is capable of identifying specific patterns in the output distributions of photons from a Boson Sampling machine. Such patterns do not allow a classical prediction of the quantum computation result, but can prove that the machine is indeed behaving in the purely quantum regime.
Another important topic of research developed in the CAPABLE project is quantum sensing. We have developed completely reconfigurable integrated photonic circuits that can be used as testbeds to implement and verify new quantum sensing protocols. In particular, we used them to assess the quantum advantage of simultaneous multi-phase estimation with respect to individual phase estimation.
Finally, we have introduced and experimentally demonstrated a new component, the quantum memristor. This device changes its transmission properties depending on the history of quantum photonic states that traversed it. This is a very critical task where one has to fine tune the minimum amount of knowledge on the quantum states of light needed to modify the device, without causing the wavefunction collapse. The quantum memristor could become a fundamental building block in future devices for quantum artificial intelligence, paving the way to a new class of quantum photonic neuromorphic circuits.
The CAPABLE project produced 42 articles in peer-reviewed journals, many of which are highly prestigious and have a very high impact factor. The results have also been disseminated in many scientific conferences, with multiple invited talks, as well as in non-technical presentations for the general public.
The results achieved in this ERC project have also been exploited scientifically in subsequent successful applications to EU calls. In addition, the PI has been awarded 2 ERC Proof-of-concept projects, DISPLAYGHT and PHOTONFAB, to investigate commercial applications. In the DISPLAYGHT project, the PI and a startup company, named VitreaLab, exploited femtosecond laser writing of waveguides for a new generation of displays with much higher efficiency and potential use as 3D holographic displays. On the other hand, the PHOTONFAB project aims at commercializing the complex and reconfigurable photonic circuits developed in CAPABLE as quantum photonic processors for future quantum computers. Ti this aim, the PI and co-workers have founded a new startup, Faro Quantum Technologies, that is currently closing its seed round of investments and has already started selling some products.
