Quantum photonic neural networks in time

Nir Rotenberg

Ivanna M. Boras Vazquez, Jacob Ewaniuk, Nir Rotenberg

We introduce the architecture and timing algorithm to realize a time-bin-encoded quantum photonic neural network (QPNN): a reconfigurable nonlinear photonic circuit inspired by the brain and trained to process quantum information. Unlike the typical spatially-encoded QPNN, time-encoded networks require the same number of photonic elements (e.g. phase shifters or switches) regardless of their size or depth. Here, we present a model of such a network and show how to include imperfections such as losses, routing errors and most notably distinguishable photons. As an example, we train the QPNN to realize a controlled-NOT gate, based on a hypothetical ideal Kerr nonlinearity. We then extend our model to a realistic two-photon nonlinearity due to scattering from a single, semiconductor quantum dot coupled to a photonic waveguide. We show that, using this realistic nonlinearity, the QPNN can be trained to act as a Bell-state analyzer which operates with a fidelity of 0.96 and at a rate only limited by losses. We further show that time gating can raise this fidelity to over 0.99, while still maintaining an efficiency exceeding 0.9. Overall, this work lays a framework for the first QPNN encoded in time, and provides a clear path to the scaling of these networks.

Chuanzhou Zhu, Tianyu Wang, Peter L. McMahon +1 more

Optical neural networks (ONNs) have been developed to enhance processing speed and energy efficiency in machine learning by leveraging optical devices for nonlinear activation and establishing connections among neurons. In this work, we propose a quantum optical neural network (QONN) that utilizes atom-cavity neurons with controllable photon absorption and emission. These quantum neurons are designed to replace the electronic components in ONNs, which typically introduce delays and substantial energy consumption during nonlinear activation. To evaluate the performance of the QONN, we apply it to the MNIST digit classification task, considering the effects of photon absorption duration, random atom-cavity detuning, and stochastic photon loss. Additionally, we introduce a convolutional QONN to facilitate a real-world satellite image classification (SAT-6) task. Due to its compact hardware and low power consumption, the QONN offers a promising solution for real-time satellite sensing, reducing communication bandwidth with ground stations and thereby enhancing data security.

Gregory R. Steinbrecher, Jonathan P. Olson, Dirk Englund +1 more

Sanjay Gupta, Royce K. P. Zia

Bhawani Shankar Leelar, E. S. Shivaleela, T. Srinivas

Artificial Neural Networks (ANNs) are computational models used in Machine Learning (ML), based on a large collection of connected simple units called artificial neurons, loosely analogous to axons in a biological brain. Most of the Neural Networks (NNs) work in classical architecture and a few hardware implementations with optical components have been proposed, which facilitates real-time parallel processing of massive data sets. While these Optical Neural Networks (ONNs) are faster and comparable in efficiency with the classical NNs, they lack in scalability and flexibility. We have proposed a scalable and reconfigurable photonic lattice based NN, similar to feedforward neural network, where photonic lattice represents the layer of the network. The superposition property of quantum computations allows photons to process massive data sets faster than electronic circuits. We explicitly tried to exploit quantum coherence for learning. Hardware implementations put restrictions on the weight space of photon as negative weights are not possible, therefore we have modified the Backpropagation algorithm for optimizing the weights of the network to manipulate the quantum states. The proposed architecture is theoretically scalable as any number of photonic lattice can be included and provides a platform to get benefit of photonic lattices with different properties. It can be used in understanding the learning behaviour of NNs in a constrained environment.