High-dimensional entanglement generation based on a Pancharatnam–Berry phase metasurface

High-dimensional entanglement is of great importance in quantum communications and can be realized by encoding information on multiple degrees of freedom(Do Fs)of the photons.Conventionally,the realization of such high-dimensional entanglement involves different combinations of bulky optical elements.In this work,we present the use of a single dielectric metasurface to generate high-dimensional entanglement by modulating multi-Do Fs of photons.By sending one of the polarization-entangled photons to interact with the metasurface,we encode path,spin angular momentum,and orbital angular momentum information to the original state.We achieve a four-qubit quantum state in the experiment.To verify it,we experimentally demonstrate the nonlocal correlations between the two photons by recording the correlated images,and we also perform a quantum state tomography measurement.This scheme can be applied to on-chip quantum state manipulation,which is promising in quantum communication with integrated components.

Surpassing the standard quantum limit of optical imaging via deep learning

The sensitivity of optical measurement is ultimately constrained by the shot noise to the standard quantum limit.It has become a common concept that beating this limit requires quantum resources.A deep-learning neural network free of quantum principle has the capability of removing classical noise from images,but it is unclear in reducing quantum noise.In a coincidence-imaging experiment,we show that quantum-resource-free deep learning can be exploited to surpass the standard quantum limit via the photon-number-dependent nonlinear feedback during training.Using an effective classical light with photon flux of about 9×10^(4) photons per second,our deep-learning-based scheme achieves a 14 dB improvement in signal-to-noise ratio with respect to the standard quantum limit.