The importance of integrated quantum photonics in the telecom band is based on the possibility of interfacing with the optical network infrastructure that was developed for classical communications. In this framework, femtosecond laser-written integrated photonic circuits, which have already been assessed for use in quantum information experiments in the 800-nm wavelength range, have great potential. In fact, these circuits, being written in glass, can be perfectly mode-matched at telecom wavelength to the in/out coupling fibers, which is a key requirement for a low-loss processing node in future quantum optical networks. In addition, for several applications, quantum photonic devices must be dynamically reconfigurable. Here, we experimentally demonstrate the high performance of femtosecond laser-written photonic circuits for use in quantum experiments in the telecom band, and we demonstrate the use of thermal shifters, which were also fabricated using the same femtosecond laser, to accurately tune such circuits. State-of-the-art manipulation of single- and two-photon states is demonstrated, with fringe visibilities greater than 95%. The results of this work open the way to the realization of reconfigurable quantum photonic circuits based on this technological platform.

## What the quantum revolution means for us

Quantum technologies promise to improve the way we do various things – from trading over the internet to performing powerful simulations for chemistry, and even engineering nanotechnology. There’s a quantum revolution going on, but it’s still a work in progress. While we can expect to develop simple quantum machines that perform specific tasks in a … Continua a leggere

## Storage and retrieval of vector beams of light in a multiple-degree-of-freedom quantum memory published in Nature Communications

The full structuration of light in the transverse plane, including intensity, phase and polarization, holds the promise of unprecedented capabilities for applications in classical optics as well as in quantum optics and information sciences. Harnessing special topologies can lead to enhanced focusing, data multiplexing or advanced sensing and metrology. Here we experimentally demonstrate the storage … Continua a leggere

## Experimental scattershot boson sampling published in Science Advances

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 … Continua a leggere

## Experimental validation of photonic boson sampling

A boson sampling device is a specialized quantum computer that solves a problem that is strongly believed to be computationally hard for classical computers. Recently, a number of small-scale implementations have been reported, all based on multiphoton interference in multimode interferometers. Akin to several quantum simulation and computation tasks, an open problem in the hard-to-simulate … Continua a leggere

## Rotated waveplates in integrated waveguide optics

Controlling and manipulating the polarization state of a light beam is crucial in applications ranging from optical sensing to optical communications, both in the classical and quantum regime, and ultimately whenever interference phenomena are to be exploited. In addition, many of these applications present severe requirements of phase stability and greatly benefit from a monolithic … Continua a leggere

## Integrated multimode interferometers with arbitrary designs for photonic boson sampling

The evolution of bosons undergoing arbitrary linear unitary transformations quickly becomes hard to predict using classical computers as we increase the number of particles and modes. Photons propagating in a multiport interferometer naturally solve this so-called boson sampling problem, thereby motivating the development of technologies that enable precise control of multiphoton interference in large interferometers. … Continua a leggere

## Anderson localization of entangled photons in an integrated quantum walk

First predicted for quantum particles in the presence of a disordered potential, Anderson localization is a ubiquitous effect, observed also in classical systems, arising from the destructive interference of waves propagating in static disordered media. Here we report the observation of this phenomenon for pairs of polarization-entangled photons in a discrete quantum walk affected by … Continua a leggere

## Three-photon bosonic coalescence in an integrated tritter

The main features of quantum mechanics reside into interference deriving from the superposition of different quantum objects. While current quantum optical technology enables two-photon interference both in bulk and integrated systems, simultaneous interference of more than two particles, leading to richer quantum phenomena, is still a challenging task. Here we report the experimental observation of … Continua a leggere

## Variational quantum process tomography of two-qubit maps

Full characterization of quantum states and processes is a fundamental requirement for verification and benchmarking of quantum devices. It has been realized in systems with few components, but for larger systems it becomes unfeasible because of the exponential growing with the system size of the number of measurements and the amount of computational power required … Continua a leggere