Bidirectional deep learning of polarization transfer in liquid crystals with application to quantum state preparation

TL;DR

This paper develops deep neural network models for accurately controlling and predicting polarization states in liquid crystals, significantly improving precision and enabling quantum state preparation.

Contribution

It introduces a bidirectional deep learning model for both direct and inverse polarization control in liquid crystals, surpassing traditional methods in accuracy.

Findings

Deep learning models outperform radial basis functions and linear interpolation in accuracy.

Achieved average infidelities of 4e-4 and 2e-4 for direct and inverse models.

Enabled local and remote quantum state preparation using the models.

Abstract

Accurate control of light polarization represents a core building block in polarization metrology, imaging, and optical and quantum communications. Voltage-controlled liquid crystals offer an efficient way of polarization transformation. However, common twisted nematic liquid crystals are notorious for lacking an accurate theoretical model linking control voltages and output polarization. An inverse model, which would predict control voltages required to prepare a target polarization, is even more challenging. Here we report both the direct and inverse models based on deep neural networks, radial basis functions, and linear interpolation. We present an inverse-direct compound model solving the problem of control voltages ambiguity. We demonstrate one order of magnitude improvement in accuracy using deep learning compared to the radial basis function method and two orders of magnitude improvement compared to the linear interpolation. Errors of the deep neural network model also decrease faster than the other methods with an increasing number of training data. The best direct and inverse models reach the average infidelities of $4 \times 10^{-4}$ and $2 \times 10^{-4}$, respectively, which is the accuracy level not reported yet. Furthermore, we demonstrate local and remote preparation of an arbitrary single-photon polarization state using the deep learning models. The results will impact the application of twisted-nematic liquid crystals, increasing their control accuracy across the board. The presented bidirectional learning can be used for optimal classical control of complex photonic devices and quantum circuits beyond interpolation.