Control of quantum light in massively multichannel networks

A.P. Danilov, V. G. Chekmachev, Alexander V. Tsukanov

Ravitej Uppu, Tom A. W. Wolterink, Willem L. Vos +2 more

Summary form only given. Quantum optics experiments require ultimate control over the propagation of light in linear optical networks to realize programmable photon correlations [1]. Integrated optics provides a robust and low-loss platform for implementing such linear optical networks. However, to achieve ultimate control on the quantum state of light, it is necessary to program the network [2]. Tuning the network for controlled multiphoton correlations involves optimization algorithms which scale inefficiently with the network size and photon number. Therefore, it is challenging to scale up this approach to massively multichannel networks, which are required for large-scale implementations of quantum information processing and quantum communication.Here, we propose a novel method to achieve ultimate control on quantum light propagation through the adaptive control of phases at input channels of a massively multichannel network. We utilize an on-chip array of 3300 nearest-neighbor coupled silicon nitride waveguides as the network. We employ complex wavefront shaping methods, which enabled the creation of programmable linear optical networks in opaque scattering media [3,4], to realize a network with programmable quantum correlations in a fixed network [5]. Using a high brightness photon-pair source, we demonstrate programmable Hong-Ou-Mandel-like bunching or antibunching of photons in a fully tunable multichannel network as predicted by our theoretical work [6]. These results enable programmable photon correlations on fixed massively multichannel optical networks with the potential for large-scale implementation of quantum simulators and quantum logic gates. We will report on the progress of this project.

Reinier van der Meer, Ravitej Uppu, Pepijn W. H. Pinkse

We study the random walk of multiple photons in a massively multichannel system. The network consists of 3300 nearest-neighbour coupled silicon nitride waveguides embedded in silica. The photon correlations arising from the quantum interference between multiple single photons is measured using an intensified CCD at the output of the network. We further aim to control the multiphoton correlations in the network by structuring the incident states of quantum light. This procedure enables a versatile platform for studying quantum correlations, such as multiphoton boson sampling, without modifying the physical system. We will report on the latest progress in this experiment.

Peter Shadbolt

Yunru Fan, Qiang Zhou

Tom A. W. Wolterink

Multiphoton quantum correlations are crucial for quantum information processing and quantum communication protocols in linear optical networks. For large-scale implementation of quantum information processing, such as quantum simulators, boson sampling or programmable quantum logic gates, a programmable functionality of a large multichannel network is required. In this thesis, we describe and demonstrate programmable quantum interference between multiple single-photon states in massively multichannel networks. Using a theoretical analysis we first show that losses in optical networks, which are unavoidable in experiments, introduce new freedom, in that the functionality of the network, and thus also quantum interference in there, is programmable to an extent not possible with lossless networks. We introduce a method to program the functionality of general multichannel linear optical networks by phase modulation of incident wavefronts, which we apply to opaque scattering media as well as integrated optics. To demonstrate quantum interference in massively multichannel networks we require a source of multiple indistinguishable single-photon states. Therefore, we have constructed and characterized a versatile quantum light source based on spontaneous parametric down-conversion. For the first time, we demonstrate two-photon quantum interference in a massively multichannel linear optical network realized in an opaque scattering medium. Using adaptive phase-modulation of the incident photons, the scattering medium is transformed to behave as a fully programmable beam splitter that is freely tunable in functionality. Exploiting this freedom, we not only show the well-known Hong-Ou-Mandel bunching of photons, but also demonstrate that this bunching can be made to vanish, or be transformed into antibunching. Our results establish opaque scattering media as a platform for massively multichannel linear optical networks with programmable quantum correlations. Finally, the high number of available channels offered by opaque scattering media can directly be employed for authentication of secure communication. We present an authenticated protocol for quantum key distribution that removes the need of an initial shared secret for authentication. Moreover, we introduce and demonstrate the first protocol for authenticated and asymmetric quantum communication, based on the quantum-secure readout of a physical unclonable function.