Paolo Mataloni

Two-Particle Bosonic-Fermionic Quantum Walk via Integrated Photonics

Quantum walk represents one of the most promising resources for the simulation of physical quantum systems, and has also emerged as an alternative to the standard circuit model for quantum computing. Here we investigate how the particle statistics, either bosonic or fermionic, influences a two-particle discrete quantum walk. Such an experiment has been realized by exploiting polarization entanglement to simulate the bunching-antibunching feature of noninteracting bosons and fermions. To this scope a novel three-dimensional geometry for the waveguide circuit is introduced, which allows accurate polarization independent behavior, maintaining remarkable control on both phase and balancement.

Integrated multimode interferometers with arbitrary designs for photonic boson sampling

Andrea Crespi, 2 Roberto Osellame, 2, ∗ Roberta Ramponi, 2 Daniel J. Brod, Ernesto F. Galvão, † Nicolò Spagnolo, Chiara Vitelli, 4 Enrico Maiorino, Paolo Mataloni, and Fabio Sciarrino ‡ Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche (IFN-CNR), Piazza Leonardo da Vinci, 32, I-20133 Milano, Italy Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci, 32, I-20133 Milano, Italy Instituto de F́ısica, Universidade Federal Fluminense, Av. Gal. Milton Tavares de Souza s/n, Niterói, RJ, 24210-340, Brazil Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 5, I-00185 Roma, Italy Center of Life NanoScience @ La Sapienza, Istituto Italiano di Tecnologia, Viale Regina Elena, 255, I-00185 Roma, Italy

Anderson localization of entangled photons in an integrated quantum walk

Researchers observe Anderson localization for pairs of polarization-entangled photons in a discrete quantum walk affected by position-dependent disorder. By exploiting polarization entanglement of photons to simulate different quantum statistics, they experimentally investigate the interplay between the Anderson localization mechanism and the bosonic/fermionic symmetry of the wave function.

Polarization entangled state measurement on a chip

We report the realization of an integrated beam splitter able to support polarization-encoded qubits. Using this device, we demonstrate quantum interference with polarization-entangled states and singlet state projection.

Experimental validation of photonic boson sampling

Nicolò Spagnolo, Chiara Vitelli, 2 Marco Bentivegna, Daniel J. Brod, Andrea Crespi, 5 Fulvio Flamini, Sandro Giacomini, Giorgio Milani, Roberta Ramponi, 5 Paolo Mataloni, 6 Roberto Osellame, 5, ∗ Ernesto F. Galvão, † and Fabio Sciarrino 6, ‡ Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 5, I-00185 Roma, Italy Center of Life NanoScience @ La Sapienza, Istituto Italiano di Tecnologia, Viale Regina Elena, 255, I-00185 Roma, Italy Instituto de F́ısica, Universidade Federal Fluminense, Av. Gal. Milton Tavares de Souza s/n, Niterói, RJ, 24210-340, Brazil Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche (IFN-CNR), Piazza Leonardo da Vinci, 32, I-20133 Milano, Italy Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci, 32, I-20133 Milano, Italy Istituto Nazionale di Ottica (INO-CNR), Largo E. Fermi 6, I-50125 Firenze, Italy

Polarization entangled states measurement on a chip

The emerging strategy to overcome the limitations of bulk quantum optics consists of taking advantage of the robustness and compactness achievable by the integrated waveguide technology. Here we report the realization of a directional coupler, fabricated by femtosecond laser waveguide writing, acting as an integrated beam splitter able to support polarization encoded qubits. This maskless and single step technique allows to realize circular transverse waveguide profiles able to support the propagation of Gaussian modes with any polarization state. Using this device, we demonstrate the quantum interference with polarization entangled states.

Complete and deterministic discrimination of polarization Bell states assisted by momentum entanglement

A complete and deterministic Bell state measurement was realized by a simple linear optics experimental scheme which adopts two-photon polarization-momentum hyperentanglement. The scheme, which is based on the discrimination among the single photon Bell states of the hyperentangled state, requires the adoption of standard single photon detectors. The four polarization Bell states have been measured with average fidelity F=0.889 +/- 0.010 by using the linear momentum degree of freedom as the ancilla. The feasibility of the scheme has been characterized as a function of the purity of momentum entanglement.

Experimental Scattershot Boson Sampling

A novel experiment supports quantum computation using photonic circuits to greatly increase quantum device speed. Boson sampling is a computational task strongly believed to be hard for classical computers, but efficiently solvable by orchestrated bosonic interference in a specialized quantum computer. Current experimental schemes, however, are still insufficient for a convincing demonstration of the advantage of quantum over classical computation. A new variation of this task, scattershot boson sampling, leads to an exponential increase in speed of the quantum device, using a larger number of photon sources based on parametric down-conversion. This is achieved by having multiple heralded single photons being sent, shot by shot, into different random input ports of the interferometer. We report the first scattershot boson sampling experiments, where six different photon-pair sources are coupled to integrated photonic circuits. We use recently proposed statistical tools to analyze our experimental data, providing strong evidence that our photonic quantum simulator works as expected. This approach represents an important leap toward a convincing experimental demonstration of the quantum computational supremacy.

Realization and Characterization of a Two-Photon Four-Qubit Linear Cluster State

Cluster states, recently introduced as a fundamental resource for one-way quantum computation, represent genuine multiqubits entangled states. The one-way model is based on the initial preparation of entangled qubits in the cluster state, followed by single qubits measurements and feed-forwards. All the difficulties present in the standard computation model, for instance the implementation of two qubits gates, are transferred in the one-way model to the state preparation.

Hyperentanglement of two photons in three degrees of freedom

A six-qubit hyperentangled state has been realized by entangling two photons in three degrees of freedom. These correspond to the polarization, the longitudinal momentum, and the indistinguishable emission produced by a two-crystal system operating with type I phase matching in the spontaneous parametric down conversion regime. The state has been characterized by a chained interferometric apparatus and its complete entangled nature has been tested by a witness criterion specifically presented for hyperentangled states. The experiment represents a realization of a genuine hyperentangled state with the maximum entanglement between the two particles allowed in the given