Published paper in Optical Materials: X on December 2019

Femtosecond Laser Irradiation followed by Chemical Etching (FLICE) is a powerful technique for prototyping three-dimensional structures in glass. Here we show that it is possible to apply FLICE also to a commercial alumino-borosilicate glass, where very complex and low-loss photonic circuitry has been demonstrated recently. As a test for the technique, we realize an optofluidic device composed of a microchannel and two intersecting optical waveguides.

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Published paper in Optica on December 2019

Scaling-up optical quantum technologies requires a combination of highly efficient multi-photon sources and integrated waveguide components. Here, we interface these scalable platforms, demonstrating high-rate three-photon interference with a quantum dot based multi-photon source and a reconfigurable photonic chip on glass. We show that this combination of scalable sources and reconfigurable photonic circuits compares favorably in performance with respect to previous implementations and that merging these platforms could allow 10-photon experiments on chip at ∼40 s−1 rate in a foreseeable future.

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Published paper in Journal of Lightwave Technology on September 2019

Phase shifters are devices that offer the possibility to dynamically reconfigure the properties of photonic integrated circuits (PICs), thus greatly extending their quality and applicability. In this paper, we provide a thorough discussion of the main problems that one can encounter when using thermal phase shifters. We show how all these issues can be solved and the performance improved by manufacturing optimized thermal shifters in femtosecond-laser-written PICs (FLW-PICs). The unprecedented results in terms of power dissipation, miniaturization and stability enable the scalable implementation of reconfigurable FLW-PICs for exploitation in many applications.

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Published paper in Physical Review Letters on August 2019

With this work, we report on the quantum storage of a heralded frequency-multiplexed single photon in an integrated laser-written rare-earth doped waveguide.  In particular, a frequency-multimode photon is stored in a praseodymium-doped waveguide using the atomic frequency comb (AFC) scheme and we demonstrate that the storage preserves the nonclassical properties of the single photon.

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Published paper in Advanced Photonics on May 2019

Boson sampling is a computational problem that has recently been proposed as a candidate to obtain an unequivocal quantum computational advantage. This prospect has stimulated much effort resulting in the experimental implementation of progressively larger devices. We review recent advances in photonic boson sampling, describing both the technological improvements achieved and the future challenges.

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Published paper in Physical Review Letters on April 2019

Decay of an excited system to its ground state is a ubiquitous phenomenon in all branches of physics. Here we use a photonic simulator to show specific and counterintuitive features of such decay in quantum systems. Significant deviations from the widely accepted exponential decay dynamics are experimentally demonstrated, in particular showing oscillatory behavior at very long decay times. Such oscillation are due to quantum interference effects and mean that in this region the decay process is not monotonic but there is the possibility that the system is re-excited by the interaction with the environment.

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Published paper in Optica on March 2019

Efforts to develop quantum computers are motivated by the promise of a tremendous speedup in several computational tasks such as quantum simulation or factoring. A milestone in this quest will be to provide evidence of quantum supremacy, which occurs when a quantum device solves a family of problems faster than state-of-the-art classical computers. The technological race toward this achievement goes hand in hand with the development of classical protocols that can discern genuine quantum processes. Here, we provide a step forward in this direction by presenting a machine-learning algorithm to detect malfunctions within a class of quantum hardware used to demonstrate quantum supremacy, relying only on experimental data.

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Published paper in Quantum Science and Technology on March 2019

Classical machine learning algorithms can provide insights on high-dimensional processes that are hardly accessible with conventional approaches. In this work we apply t-distributed Stochastic Neighbor Embedding (t-SNE) to probe the spatial distribution of n-photon events in m-dimensional Hilbert spaces, showing that its findings can be beneficial for validating genuine quantum interference in boson sampling experiments. We envisage that this approach will inspire further theoretical investigations, for instance for a reliable assessment of quantum computational advantage.

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