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.

Liquid crystal devices for vector vortex beams manipulation and quantum information applications [Invited]

Vector vortex beams(VVBs) have attracted significant attention in both classical and quantum optics. Liquid crystal(LC),beyond its applications in information display, has emerged as a versatile tool for manipulating VVBs. In this review, we focus on the functions and applications of typical LC devices in recent studies on controlling the space-variant polarized vortex light. Manipulation of VVBs through patterned nematic LC optical elements, patterned cholesteric LC optical elements, self-assembled defects, and LC spatial light modulators is discussed separately. Moreover, LC-based novel optical applications in the field of quantum information are reviewed.

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.