arXiv subjects

En-Ze Li

Publications and source records attributed to En-Ze Li.

12 recordsLinked to original sources

arXiv2025

All-optical convolution utilizing processing in memory based on a cold atomic ensemble

Processing in memory (PIM) has received significant attention due to its high efficiency, low latency, and parallelism. In optical computation, coherent memory is a crucial infrastructure for PIM frameworks. This study presents an all-optical convolution experiment conducted within computational storage based on a cold atomic ensemble. By exploiting the light-atom phase transfer facilitated by the electromagnetically induced transparency, we demonstrated spiral phase contrast processing of photon images in memory, resulting in the edge enhancement of retrieved images recorded using time-correlated photon imaging. In particular, adopting state-of-the-art atomic techniques provides a coherent memory lifetime exceeding 320 us for PIM operations. Our results highlight the significant potential of cold atomic ensembles as computational storage for developing all-optical PIM systems.

physics.app-ph↗

arXiv2024

On Chip Quantum States Generation by Incoherent Light

On-chip quantum sources based on nonlinear processes are pivotal components in integrated photonics, driving significant advancements in quantum information technologies over recent decades. Usually, the pump coherence has been considered to be crucial for ensuring the quality of generated states, therefore incoherent light is rarely used in quantum information processing. In this work, we explore and reveal the constructive influence of pumped temporal incoherence on the quantum properties of photon sources. Taking silicon waveguides as nonlinear media, we theoretically show that temporal incoherence of light can improve pumping utilization efficiency, resulting in higher source brightness in a spontaneous four-wave mixing process, and the spectrally uncorrelated nature of incoherent light is transferred to the generated photon source, allowing high-purity state preparation. Experimentally, we obtain a higher photon pair generation rate and the lower heralded second-order autocorrelation with an Amplified Spontaneous Emission source. Additionally, we successfully generate a polarization-entangled state with Bell inequality violation of S = 2.64 and a fidelity of 95.7%. Our study reveals the mechanism behind incoherently pumped quantum states and presents a method for generating photon sources using an easily accessible incoherent light.

quant-ph↗

arXiv2024

Exceptional point and hysteresis trajectories in cold Rydberg atomic gases

The interplay between strong long-range interactions and the coherent driving contribute to the formation of complex patterns, symmetry, and novel phases of matter in many-body systems. However, long-range interactions may induce an additional dissipation channel, resulting in non-Hermitian many-body dynamics and the emergence of exceptional points in spectrum. Here, we report experimental observation of interaction-induced exceptional points in cold Rydberg atomic gases, revealing the breaking of charge-conjugation parity symmetry. By measuring the transmission spectrum under increasing and decreasing probe intensity, the interaction-induced hysteresis trajectories are observed, which give rise to non-Hermitian dynamics. We record the area enclosed by hysteresis loops and investigate the dynamics of hysteresis loops. The reported exceptional points and hysteresis trajectories in cold Rydberg atomic gases provide valuable insights into the underlying non-Hermitian physics in many-body systems, allowing us to study the interplay between long-range interactions and non-Hermiticity.

cond-mat.quant-gas↗

arXiv2024

All-optically tunable enantio-selectivity and chirality transfer

Detecting and controlling the chirality of materials play an essential role in exploring nature, providing new avenues for material creation, discrimination, and manipulation. In such tasks, chiral reagents are essential in defining or enhancing the chiral dichroism response. However, ignoring their influences on the symmetry of the medium hamper the ability to control and induce asymmetric synthesis. Here, we propose a simple but versatile chirality transfer method for synthesizing and manipulating the chirality of medium. The proposed method induces the dispersion of light in a neutral atomic system, allowing to deterministically and tunably control the chirality transfer using a helical field. First, we theoretically analyze the mechanism for this optically induced chirality transfer. Afterwards, we experimentally study the enantio-sensitive feature of the medium exposed to the auxiliary chiral field. This result can be suppressed or enhanced in a deterministic enantio-selection, opening up an efficient way to manipulate asymmetric synthesis.

physics.optics↗

arXiv2024

Non-Hermitian unidirectional routing of photonic qubits

Efficient and tunable qubit unidirectional routers and spin-wave diodes play an important role in both classical and quantum information processing domains. Here, we reveal that multi-level neutral cold atoms can mediate both dissipative and coherent couplings. Interestingly, we investigate and practically implement this paradigm in experiments, successfully synthesizing a system with dual functionality as both a photonic qubit unidirectional router and a spin-wave diode. By manipulating the helicity of the field, we can effectively balance the coherence coupling and dissipative channel, thereby ensuring the unidirectional transfer of photonic qubits. The qubit fidelity exceeds 97.49%, and the isolation ratio achieves $16.8\pm0.11$ dB while the insertion loss is lower than 0.36 dB. Furthermore, we show that the spin-wave diode can effectively achieve unidirectional information transfer by appropriately setting the coherent coupling parameters. Our work not only provides new ideas for the design of extensive components in quantum networks, but also opens up new possibilities for non-Hermitian quantum physics, complex quantum networks, and unidirectional quantum information transfer.

quant-ph↗

arXiv2023

Optical Memory for Arbitrary Perfect Poincar\'e States in an Atomic Ensemble

Inherent spin angular momentum (SAM) and orbital angular momentum (OAM) which manifest as polarization and spatial degrees of freedom (DOF) of photons, hold a promise of large capability for applications in classical and quantum information processing. To enable these photonic spin and orbital dynamic properties strongly coupled with each other, Poincar\'{e} states have been proposed and offer advantages in data multiplexing, information encryption, precision metrology, and quantum memory. However, since the transverse size of Laguerre Gaussian beams strongly depends on their topological charge numbers $\left| l \right|$, it is difficult to store asymmetric Poincar\'{e} states due to the significantly different light-matter interaction for distinct spatial modes. Here, we experimentally realize the storage of perfect Poincar\'{e} states with arbitrary OAM quanta using the perfect optical vortex, in which 121 arbitrarily-selected perfect Poincar\'{e} states have been stored with high fidelity. The reported work has great prospects in optical communication and quantum networks for dramatically increased encoding flexibility of information.

quant-ph↗

arXiv2023

High-dimensional frequency conversion in hot atomic system

One of the major difficulties in realizing a high-dimensional frequency converter for conventional optical vortex (COV) stems from the difference in ring diameter of COV modes with different topological charge numbers l. Here, we implement a high-dimensional frequency convertor for perfect optical vortex (POV) modes with invariant size through the four-wave mixing (FWM) process by utilizing Bessel-Gaussian beams instead of Laguerre-Gaussian beams. The measured conversion efficiency from 1530 nm to 795 nm is independent of l at least in subspace of {-6,...,6}, and the achieved conversion fidelities for two-dimensional (2D) superposed POV states exceed 97%. We further realize the frequency conversion of 3D, 5D and 7D superposition states with fidelities as high as 96.70%, 89.16% and 88.68%, respectively. The reported scheme is implemented in hot atomic vapor, it's also compatible with the cold atomic system and may find applications in high-capacity and long-distance quantum communication.

physics.optics↗

arXiv2022

Detection of infrared light through stimulated four-wave mixing process

Infrared optical measurement has a wide range of applications in industry and science, but infrared light detectors suffer from high costs and inferior performance than visible light detectors. Four-wave mixing (FWM) process allows detection in the infrared range by detecting correlated visible light. We experimentally investigate the stimulated FWM process in a hot $^{85}$Rb atomic vapor cell, in which a weak infrared signal laser at $1530~$nm induces the FWM process and is amplified and converted into a strong FWM light at $780~$nm, the latter can be detected more easily. We find the optimized single- and two-photon detunings by studying the dependence of the frequency of input laser on the generated FWM light. What's more, the power gain increases rapidly as the signal intensity decreases, which is consistent with our theoretical analysis. As a result, the power gain can reach up to 500 at a signal laser power of $0.1~\mu$W and the number of detected photons increased by a factor of 250. Finally, we experimentally prove that our amplification process can work in a broad band in the frequency domain by exploring the response rate of our stimulated FWM process.

physics.optics↗

arXiv2021

Synchronized resistance to inhomogeneous magnetic field-induced dephasing of an image stored in a cold atomic ensemble

Long-lived storage of arbitrary transverse multimodes is important for establishing a high-channel-capacity quantum network. Most of the pioneering works focused on atomic diffusion as the dominant impact on the retrieved pattern in an atom-based memory. In this work, we demonstrate that the unsynchronized Larmor precession of atoms in the inhomogeneous magnetic field dominates the distortion of the pattern stored in a cold-atom-based memory. We find that this distortion effect can be eliminated by applying a strong uniform polarization magnetic field. By preparing atoms in magnetically insensitive states, the destructive interference between different spin-wave components is diminished, and the stored localized patterns are synchronized further in a single spin-wave component; then, an obvious enhancement in preserving patterns for a long time is obtained. The reported results are very promising for studying transverse multimode decoherence in storage and high-dimensional quantum networks in the future.

quant-ph↗

arXiv2019

Experimental realization of quantum non-reciprocity based on cold atomic ensembles

In analog to counterparts widely used in electronic circuits, all optical non-reciprocal devices are basic building blocks for both classical and quantum optical information processing. Approaching the fundamental limit of such devices, where the propagation of a single photon exhibits a good non-reciprocal characteristic, requires an asymmetric strong coupling between a single photon and a matter. Unfortunately it has been not realized yet. Here, we propose and experimentally realize a quantum non-reciprocity device with low optical losses and a high isolation of larger than 14 dB based on the cold atoms. Besides, the non-reciprocal transmission of a quantum qubit and non-reciprocal quantum storage of a true single photon are also realized. All results achieved would be very promising in building up quantum non-reciprocal devices for quantum networks.

quant-ph↗

arXiv2019

Experimental demonstration of Cavity-Free Optical Isolators and Optical Circulators

Cavity-free optical nonreciprocity components, which have an inherent strong asymmetric interaction between the forward- and backward-propagation direction of the probe field, are key to produce such as optical isolators and circulators. According to the proposal presented by Xia et al., [Phys. Rev. Lett. 121, 203602 (2018)], we experimentally build a device that uses cross-Kerr nonlinearity to achieve a cavity-free optical isolator and circulator. Its nonreciprocal behavior arises from the thermal motion of N-type configuration atoms, which induces a strong chiral cross-Kerr nonlinear response for the weak probe beam. We obtain a two-port optical isolator for up to 20 dB of isolation ratio in a specially designed Sagnac interferometer. The distinct propagation directions of the weak probe field determine its cross-phase shift and transmission, by which we demonstrate the accessibility of a four-port optical circulator.

quant-ph↗

arXiv2019

Temporal Wheeler's delayed-Choice Experiment based on Cold Atomic Quantum Memory

Nowadays the most intriguing features of wave particle complementarity of single photon is exemplified by the famous Wheeler's delayed choice experiment in linear optics, nuclear magnetic resonance and integrated photonic device systems. Studying the wave particle behavior in light and matter interaction at single photon level is challenging and interesting, which gives how single photons complement in light and matter interaction. Here, we demonstrate a Wheeler's delayed choice experiment in an interface of light and atomic memory, in which the cold atomic memory makes the heralded single photon divided into a superposition of atomic collective excitation and leaked pulse, thus acting as memory beam splitters. We observe the morphing behavior between particle and wave of a heralded single photon by changing the relative proportion of quantum random number generator, the second memory efficiency, and the relative storage time of two memories. The reported results exhibit the complementarity behavior of single photon under the interface of light atom interaction.

quant-ph↗