**3D-QUEST – 3D-Quantum Integrated Optical SimulationFunding programme:** ERC Starting Grant-Consolidator

**Overall funding:**€ 1,474,800

**Grant agreement no:**307783

**Period:**1 August 2012-31 July 2017

**Principal Investigator:**Fabio Sciarrino, Department of Physics, University of Roma “La Sapienza”

**CNR, Italy – R. Osellame**

Partner:

Partner:

## The vision of 3D-QUEST

3D-QUEST exploited the potential of the femtosecond laser writing integrated waveguides. This technique adopted to realize 3-dimensional capabilities and high flexibility, bringing in this way the optical quantum simulation into a new regime.

Quantum information was born from the merging of classical information and quantum physics. Its main objective consists of understanding the quantum nature of information and learning how to process it by using physical systems which operate by following quantum mechanics laws. Quantum simulation was a fundamental instrument to investigate phenomena of quantum systems dynamics, such as quantum transport, particle localizations and energy transfer, quantum-to-classical transition, and even quantumimproved computation, all tasks that were hard to simulate with classical approaches.

Within this framework integrated photonic circuits have a strong potential to realize quantum information processing by optical systems.

The aim of 3D-QUEST was to develop and implement quantum simulation by exploiting 3-dimensional integrated photonic circuits. 3D-QUEST was structured to demonstrate the potential of linear optics to implement a computational power beyond the one of a classical computer. Such “hard-to-simulate” scenario was disclosed when multiphoton-multimode platforms were realized. The 3D-QUEST research program focused on three tasks of growing difficulty.

A-1. To simulate bosonic-fermionic dynamics with integrated optical systems acting on 2 photon entangled states.

A-2. To pave the way towards hard-to-simulate, scalable quantum linear optical circuits by investigating m-port interferometers acting on n-photon states with n>2.

A-3. To exploit 3-dimensional integrated structures for the observation of new quantum optical phenomena and for the quantum simulation of more complex scenarios.

## Boson sampling

Photons naturally solve the BosonSampling problem: sample the outputs of a multi-photon experiment in a linear-optical interferometer. This is strongly believed to be hard to do on a classical computer, and motivates the development of technologies that enable precise control of multi-photon interference in large interferometers. Here we report multi-photon experiments in a 5-mode integrated interferometer. We use novel three-dimensional manufacturing techniques to achieve simultaneous control of 25 independent parameters that describe an arbitrary interferometer. We characterize the chip using one- and two-photon experiments, and confirm the quantum mechanical predictions for three-photon interference. Scaled up versions of this setup are the most promising way to demonstrate the computational capability of quantum systems, and may have applications in high-precision measurements and quantum communication.

## Quantum simulation

Quantum information was born from the merging of classical information and quantum physics. Its main objective consists of understanding the quantum nature of information and learning how to process it by using physical systems which operate by following quantum mechanics laws. Quantum simulation is a fundamental instrument to investigate phenomena of quantum systems dynamics, such as quantum transport, particle localizations and energy transfer, quantum-to-classical transition, and even quantum improved computation, all tasks that are hard to simulate with classical approaches. Within this framework integrated photonic circuits have a strong potential to realize quantum information processing by optical systems.

## Quantum interferometry

The aim of quantum sensing is to develop methods to extract the maximum amount of information from a system with minimal disturbance upon it. In the case of optical interferometry, the parameter to be estimated is an optical phase introduced by a sample. Within this context, it has been shown that the possibility of exploting quantum resources can increase the achievable precision going beyond the semiclassical regime of operation. This approach can have wide applications for minimally invasive sensing methods in order to extract the maximum amount of information from a system with minimal disturbance.