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QUCHIP Report Summary

Project ID: 641039
Funded under: H2020-EU.1.2.2.

Periodic Reporting for period 1 - QUCHIP (Quantum Simulation on a Photonic Chip)

Reporting period: 2015-03-01 to 2016-08-31

Summary of the context and overall objectives of the project

QUCHIP project aims at boosting the development of photonic quantum technologies towards realization of complex tasks. Indeed, the adoption of quantum systems has all the potential to bring a second quantum technological revolution, opening the way to solving computation and simulation tasks beyond the capabilities of classical devices. Indeed, the complex interference patterns which takes place when multiple bosons interact in a large interferometer are known to be classically intractable and to constitute a viable platform for simulations of more general quantum systems.
Being able to reach the so-called “quantum supremacy”, where the quantum advantage is substantial, requires still large technological advancements. This implies pushing the limits of current technologies for photon generation, manipulation and detection, and to find innovative schemes towards scalability of photonic platforms. Photonic sources have been realized in the form of array architectures on-chip and of polarization-entangled state generators. Fully-reconfigurable planar circuits have been realized, finally closing the “universality loophole” in an integrated device, and proper design through numerical simulation as well as hardware implementation of integrated detectors have been performed.
The ability to generate single photons, to make them evolve through a complex integrated circuit and finally to detect the final output state are the key ingredients for photonic quantum technologies, in particular for the implementation of a pivotal instrument, the quantum walk. The latter is the analog of the classical walk with additional ingredients such as superposition and parallelism. QUCHIP partners contributed in enhancing the size and the complexity of current, standard implementations, and in exploring new directions, such as going beyond unidimensional walks (quantum walks on a plane), using time instead of spatial encoding (time-bin quantum walks) or featuring the creation of additional photons in the middle of the state evolution (active quantum walks). A major focus has been devoted to the study of a special case of quantum walks, known as Boson Sampling, that presents a strong theoretical evidence of computational hardness.
Boson Sampling can as well be exploited as a “minimal” instance of quantum simulation, where the very formulation of the problem aims at maximizing the evidence for hard-computability. QUCHIP partners have also investigated quantum simulations of more specific natural processes, such as spin chains evolution or perfect state transfer, highlighting the versatility of photonic platforms.
Finally, the objective of overtaking of classical devices requires an extensive treatment on the certification side. Exquisite control over the system’s parameters will be mandatory in the future large-scale implementations, and efficient verification techniques for problems as hard as Boson Sampling will be needed for unambiguous proofs against extended Church-Turing thesis with quantum walks. Several validation techniques have been implemented in QUCHIP, ranging from on-chip entanglement tests after spin chain simulation to the assessment of genuine multiparticle interference through observation of suppression laws.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The overall development plan in the QUCHIP collaboration is organized in four interrelated work-packages: multiphoton quantum walks, Boson Sampling, photonic quantum technologies and simulated quantum phenomena.
In WP1 – Multiphoton Quantum Walks, QUCHIP has contributed in two directions, by enhancing the size and the complexity of standard implementations, and by exploring new possibilities, such as going beyond unidimensional walks. On the verification side, the effects of photonic clouding have been exploited to highlight the transition from a structured quantum walk to a random one.
WP2 focuses on Boson Sampling, a special case of quantum walk corresponding to the case in which the unitary evolution is completely random and the input is a pure, collision-free bosonic Fock state. Both passive and active interferometers have been used for Boson Sampling in QUCHIP, and investigations have been performed to investigate the robustness of the problem’s computational hardness. Several results came on the verification side, with the observation of generalized suppression laws in both planar and 3D symmetric interferometers.
The activities of WP3 – Photonic Quantum Technologies are directed towards pushing the limits of current technologies for photon generation, manipulation and detection. QUCHIP partners are involved into research among all of these areas, including realization of photonic sources, fully-reconfigurable planar circuits, and hardware implementation of integrated detectors .
Finally, within WP4 – Simulated Quantum Phenomena, the QUCHIP partners have investigated quantum simulations of physical processes, such as spin chains evolution or perfect state transfer. Classical simulations of quantum systems were characterized as well. Again, verification of the results’ correctness have been carried out, this time by the first on-chip verification of entanglement volume-law growth.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Information science has had a transformative action in our society, changing its dynamics and even the way that people relate. This evolution will keep happening over the next years, and, in order to strengthen its leadership position in science and its ability of industrial innovation, Europe needs to invest in future technologies with a clear view of the forefront of information science, and an understanding of the concrete industrial capabilities. As in 2008, the world market for photonic products was worth €277bn, with communications, information technology, and measurements amounting to nearly one third of this market [source: the Cordis report on the leverage of the photonics industry]. Quantum Technologies are one of the priorities of the European Union, as emphasized by the European Flagship program on this field which programs a strong increase in the interconnection between the different research institutes.
Quantum simulation has an enormous potential: realizing it with photonics hardware may disclose a completely new technological scenario with a direct influence to the European industries involved in the photonics market. The ambition of QUCHIP is to foster the new generations of quantum technologies. The adoption of advanced technical solutions for quantum photonics, such as integrated structures, is a recent development of the field, which has so far happened by virtue of the initiative of individual groups. At present, coordination between diverse activities has been implemented by effective, yet sparse collaborations. From the scientific point of view, QUCHIP aims at not dispersing the momentum that quantum photonics has acquired in the last years by coordinating the actions of its partners, and by facilitating the interaction with industrial partners. The consortium will develop solutions to major roadblocks for future maturation of photonic quantum simulators. A QUCHIP partner has applied to a FET Innovation Launchpad program, to investigate the marketing opportunities of one QUCHIP result. Another QUCHIP partner, the University of Bristol, together with other academic and industrial partners, has started Quantum Technology Program to train and support entrepreneurs and to enable them to start up companies based on quantum technologies.

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