Experimental Demonstration Research Articles

Stabilizer entropy of quantum tetrahedra

How complex is the structure of quantum geometry? In several approaches, the spacetime atoms are obtained by the SU(2) intertwiner called quantum tetrahedron. The complexity of this construction has a concrete consequence in recent efforts to simulate such models and toward experimental demonstrations of quantum gravity effects. There are, therefore, both a computational and an experimental complexity inherent to this class of models. In this paper, we study this complexity under the lens of (SE). We calculate the SE of the gauge-invariant basis states and its average in the SU(2)-gauge invariant subspace. We find that the states of definite volume are singled out by the (near) maximal SE and give precise bounds to the verification protocols for experimental demonstrations on available quantum computers. Published by the American Physical Society 2024

Enhancing secure transmission and key distribution for ultrahigh-order QAM via delta-sigma modulation and discrete memristive-enhanced chaos.

In this Letter, we propose a method for ultrahigh-order QAM secure transmission and key distribution based on delta-sigma modulation (DSM) and discrete memristive-enhanced chaos (DMEC). The disturbance vectors generated by the DMEC scramble the DSM signals in both frequency and time domains, resulting in highly secure DSM signals. Through the key modulation and power adjustment and then superimposing them on the encrypted signals, the method achieves simultaneous transmission of keys and signals without the need for additional spectral resources. This approach allows for secure communication with continuous key iteration and updates, offering an effective solution for implementing "one-time pad" encryption. In the experimental demonstration, we achieved a secure transmission and key distribution of a 16384QAM signal at a rate of 17.09 Gb/s over 25 km in an intensity-modulated direct detection (IMDD) system, based on DSM.

Enhanced quantum state transfer by circumventing quantum chaotic behavior

The ability to realize high-fidelity quantum communication is one of the many facets required to build generic quantum computing devices. In addition to quantum processing, sensing, and storage, transferring the resulting quantum states demands a careful design that finds no parallel in classical communication. Existing experimental demonstrations of quantum information transfer in solid-state quantum systems are largely confined to small chains with few qubits, often relying upon non-generic schemes. Here, by using a superconducting quantum circuit featuring thirty-six tunable qubits, accompanied by general optimization procedures deeply rooted in overcoming quantum chaotic behavior, we demonstrate a scalable protocol for transferring few-particle quantum states in a two-dimensional quantum network. These include single-qubit excitation, two-qubit entangled states, and two excitations for which many-body effects are present. Our approach, combined with the quantum circuit’s versatility, paves the way to short-distance quantum communication for connecting distributed quantum processors or registers, even if hampered by inherent imperfections in actual quantum devices.

Experimental Demonstration of a Tunable Energy-Selective Gamma-Ray Imaging System Based on Recoil Electrons

The domain of gamma-ray imaging necessitates technological advancements to surmount the challenge of energy-selective imaging. Conventional systems are constrained in their dynamic focus on specific energy ranges, a capability imperative for differentiating gamma-ray emissions from diverse sources. This investigation introduces an innovative imaging system predicated on the detection of recoil electrons, addressing the demand for adjustable energy selectivity. Our methodology encompasses the design of a gamma-ray imaging system that leverages recoil electron detection to execute energy-selective imaging. The system’s efficacy was investigated experimentally, with emphasis on the adaptability of the energy selection window. The experimental outcomes underscore the system’s adeptness at modulating the energy selection window, adeptly discriminating gamma rays across a stipulated energy spectrum. The results corroborate the system’s adaptability, with an adjustable energy resolution that coincides with theoretical projections and satisfies the established criteria. This study affirms the viability and merits of utilizing recoil electrons for tunable energy-selective gamma-ray imaging. The system’s conceptualization and empirical validation represent a notable progress in gamma-ray imaging technology, with prospective applications extending from medical imaging to astrophysics. This research sets a solid foundation for subsequent inquiries and advancements in this domain.

Single domain generalization method based on anti-causal learning for rotating machinery fault diagnosis

Single-domain generalization (SDG) fault diagnosis methods are promising approach because they can diagnose unknown domains by training only one domain. However, there have been fewer studies on fault diagnosis for SDG. Existing studies focus on extending the distribution of source domain, but fail to consider how to estimate domain shifts between domains. Therefore, we propose an SDG fault diagnosis learning paradigm, i.e., simulation-inference-adaptation, which first establishes a pseudo-domain as the target domain to simulate the domain shifts, then reasons the causes of the domain shifts, and finally performs the domain adaptation. In this paradigm, an anti-causal learning approach is proposed, whereby the cause of the domain shifts between the pseudo-domain and the source domain is inferred during training and the learned knowledge is used to analyze the cause of the domain shifts between the target domain and the source domain during testing. Specifically, data augmentation is utilized to perform combinatorial transformation of source data to generate pseudo-domains, perform anti-causal inference to learn to discover causal factors for domain shift between pseudo-domains and source domains, and impose the inferred causality into a weighted domain adaptation network. Finally, the experimental demonstration validated the proposed method's validity and its ability to inference causality.

Role of spatial coherence in diffractive optical neural networks

Diffractive optical neural networks (DONNs) have emerged as a promising optical hardware platform for ultra-fast and energy-efficient signal processing for machine learning tasks, particularly in computer vision. Previous experimental demonstrations of DONNs have only been performed using coherent light. However, many real-world DONN applications require consideration of the spatial coherence properties of the optical signals. Here, we study the role of spatial coherence in DONN operation and performance. We propose a numerical approach to efficiently simulate DONNs under incoherent and partially coherent input illumination and discuss the corresponding computational complexity. As a demonstration, we train and evaluate simulated DONNs on the MNIST dataset of handwritten digits to process light with varying spatial coherence.

Eagle-Eye Inspired Meta-Device for Phase Imaging.

The dual-focus vision observed in eagles' eyes is an intriguing phenomenon captivates scientists since a long time. Inspired by this natural occurrence, the authors' research introduces a novel bifocal meta-device incorporating a polarized camera capable of simultaneously capturing images for two different polarizations with slightly different focal distances. This innovative approach facilitates the concurrent acquisition of underfocused and overfocused images in a single snapshot, enabling the effective extraction of quantitative phase information from the object using the transport of intensity equation. Experimental demonstrations showcase the application of quantitative phase imaging to artificial objects and human embryonic kidney cells, particularly emphasizing the meta-device's relevance in dynamic scenarios such as laser-induced ablation in human embryonic kidney cells. Moreover, it provides a solution for the quantification during the dynamic process at the cellular level. Notably, the proposed eagle-eye inspired meta-device for phase imaging (EIMPI), due to its simplicity and compact nature, holds promise for significant applications in fields such as endoscopy and headsets, where a lightweight and compact setup is essential.

Exploring the Reconfigurable Memory Effect in Electroforming-Free YMnO3-Based Resistive Switches: Towards a Tunable Frequency Response.

Memristors, since their inception, have demonstrated remarkable characteristics, notably the exceptional reconfigurability of their memory. This study delves into electroforming-free YMnO3 (YMO)-based resistive switches, emphasizing the reconfigurable memory effect in multiferroic YMO thin films with metallically conducting electrodes and their pivotal role in achieving adaptable frequency responses in impedance circuits consisting of reconfigurable YMO-based resistive switches and no reconfigurable passive elements, e.g., inductors and capacitors. The multiferroic YMO possesses a network of charged domain walls which can be reconfigured by a time-dependent voltage applied between the metallically conducting electrodes. Through experimental demonstrations, this study scrutinizes the impedance response not only for individual switch devices but also for impedance circuitry based on YMO resistive switches in both low- and high-resistance states, interfacing with capacitors and inductors in parallel and series configurations. Scrutinized Nyquist plots visually capture the intricate dynamics of impedance circuitry, revealing the potential of electroforming-free YMO resistive switches in finely tuning frequency responses within impedance circuits. This adaptability, rooted in the unique properties of YMO, signifies a paradigm shift heralding the advent of advanced and flexible electronic technologies.

Breakdown of argon by a train of high-repetition long-wave-infrared pulses from a free-electron laser oscillator

This study presents an experimental demonstration of laser-induced breakdown in argon, employing a free-electron laser with a wavelength of 10 μm and a repetition rate of 2.856 GHz. Despite the fluence of individual laser pulses being an order of magnitude smaller than the breakdown threshold, cascade ionization developed in the pulse train, leading to breakdown. The breakdown probability within a finite pulse train increases with gas pressure, and it was notably enhanced in a gas chamber with poor cleanliness. Numerical simulations of cascade ionization replicated the experimental results. The simulation revealed that breakdown phenomena are governed by the balance between avalanche multiplication of electrons within laser pulses and electron diffusion during pulse intervals.

Hybrid fiber-based time synchronization and vibration detection system.

We propose a hybrid fiber-based time synchronization and vibration detection system. The vibration is detected by exploring the idle light of the time synchronization system, i.e., the Rayleigh backscattering of the timing pulse disseminated in the fiber link. The addition of a sensing function does not affect the performance of time synchronization. In the multiuser experimental demonstration, time deviation results are 3.6 ps at τ = 1 s and 1.4 ps at τ = 104 s on the 40-km fiber link. Meanwhile, the hybrid system can accurately detect and locate vibrations occurring on the link. This method enables multiple functions of the optical fiber network without occupying extra optical channels. Moreover, it gives a possible solution for enhancing the security of the time synchronization network through vibration detection.

On-chip source-device-independent quantum random number generator

Quantum resources offer intrinsic randomness that is valuable for applications such as cryptography, scientific simulation, and computing. Silicon-based photonics chips present an excellent platform for the cost-effective deployment of next-generation quantum systems on a large scale, even at room temperature. Nevertheless, the potential susceptibility of these chips to hacker control poses a challenge in ensuring security for on-chip quantum random number generation, which is crucial for enabling extensive utilization of quantum resources. Here, we introduce and implement an on-chip source-device-independent quantum random number generator (SDI-QRNG). The randomness of this generator is achieved through distortion-free on-chip detection of quantum resources, effectively eliminating classical noise interference. The security of the system is ensured by employing on-chip criteria for estimating security entropy in a practical chip environment. By incorporating a photoelectric package, the SDI-QRNG chip achieves a secure bit rate of 146.2 Mbps and a bare chip rate of 248.47 Gbps, with all extracted secure bits successfully passing the randomness test. Our experimental demonstration of this chip-level SDI-QRNG shows significant advantages in practical applications, paving the way for the widespread and cost-effective implementation of room-temperature secure QRNG, which marks a milestone in the field of QRNG chips.

Rydberg-atom experiment for the integer factorization problem

The task of factoring integers poses a significant challenge in modern cryptography, and quantum computing holds the potential to efficiently address this problem compared to classical algorithms. Thus, it is crucial to develop quantum computing algorithms to address this problem. This study introduces a quantum approach that utilizes Rydberg atoms to tackle the factorization problem. Experimental demonstrations are conducted for the factorization of small composite numbers such as 6=2×3, 15=3×5, and 35=5×7. This approach involves employing Rydberg-atom graphs to algorithmically program binary multiplication tables, yielding many-body ground states that represent superpositions of factoring solutions. Subsequently, these states are probed using quantum adiabatic computing. Limitations of this method are discussed, specifically addressing the scalability of current Rydberg quantum computing for the intricate computational problem. Published by the American Physical Society 2024

Non-Abelian Braiding of Topological Edge Bands.

Braiding is a geometric concept that manifests itself in a variety of scientific contexts from biology to physics, and has been employed to classify bulk band topology in topological materials. Topological edge states can also form braiding structures, as demonstrated recently in a type of topological insulators known as Möbius insulators, whose topological edge states form two braided bands exhibiting a Möbius twist. While the formation of Möbius twist is inspiring, it belongs to the simple Abelian braid group B_{2}. The most fascinating features about topological braids rely on the non-Abelianness in the higher-order braid group B_{N} (N≥3), which necessitates multiple edge bands, but so far it has not been discussed. Here, based on the gauge enriched symmetry, we develop a scheme to realize non-Abelian braiding of multiple topological edge bands. We propose tight-binding models of topological insulators that are able to generate topological edge states forming non-Abelian braiding structures. Experimental demonstrations are conducted in two acoustic crystals, which carry three and four braided acoustic edge bands, respectively. The observed braiding structure can correspond to the topological winding in the complex eigenvalue space of projective translation operator, akin to the previously established point-gap winding topology in the bulk of the Hatano-Nelson model. Our Letter also constitutes the realization of non-Abelian braiding topology on an actual crystal platform, but not based on the "virtual" synthetic dimensions.

Development of hybrid photonic integrated wavelength-tunable laser at 2 µm and its application to FMCW LiDAR

This paper reports on the experimental demonstration of a fully integrated frequency-modulated continuous-wave (FMCW) LiDAR sensing system, operating at 2.0 µm. It makes use of a widely tunable hybrid external cavity laser based on the combination of GaSb gain chip and silicon waveguide circuits. The single-frequency laser operation over the full spectral bandwidth of the gain chip is secured using a frequency-selective filter, consisting of two sequential microring resonators in a Vernier configuration. To increase the mode-hop free wavelength tuning range while preserving the linewidth of the laser, the heater of the phase section placed along the bus waveguide is synchronously controlled with two independent heaters placed on each microring resonator. This laser is then implemented for the development of an FMCW LiDAR, consisting of all-optical fiber-based two independent unbalanced Mach-Zehnder interferometers: k-space interferometer for the linearization of continuously swept laser frequency and main interferometer for the measurement of the distributed back-reflection over the distance. The optical frequency of the laser is continuously swept over a ∼100 GHz range (or Δλ=1.47 nm at the operating wavelength) at a modulation speed of 100 Hz. Using this wavelength tunable laser, a light detection and ranging system (LiDAR) is experimentally demonstrated, showing a very high axial resolution of 1.36 mm in air with an extremely high precision of ∼9 µm at a 100 Hz measurement rate.

Experimental demonstration of positioning the cooperation terminal for underwater wireless optical communication based on visual navigation

Underwater wireless optical communication (UWOC) is a useful way to transmit a large volume of data in ocean engineering. In application, one of the UWOC terminals is usually carried on an underwater robot to actively adjust its orientation and position to establish an optical link, which requires the mobile terminal to locate the cooperation partner. At a short communication distance, visual navigation is a preferred method to measure the position. In this method, a camera is installed on the mobile terminal while several light-emitting diodes (LEDs) are in the cooperation one. In the image of the camera, by capturing the pattern formed of LEDs light spots, the relative position and orientation between terminals could be calculated. However, in a UWOC system, visual navigation is interfered with by the UWOC transmitter since it forms an additional light spot in the camera’s image. To solve this issue, we present a UWOC-compatible visual navigation method, in which the UWOC light spot is distinguished with the hue, saturation, and value (HSV) color model. Then, we experimentally demonstrate the effectiveness of the method in a pool, applying signals with different bitrates and power on the transmitter. The results show that, while the distance between terminals is within 350 cm and the yaw angle is within 5°, the measured errors are within 1.77 cm and 0.92°, respectively, which is accurate enough for most UWOC applications. The method presented in this paper is simple, pragmatic, and useful for establishing a UWOC link.

A radiometric model for demonstration of exoplanets detection by the transit method

This work describes an exact radiometric model for experimental demonstrators of the detection of exoplanets by the transit method. This model generalises the calculation of the depth of occultation from the standard transit method to the case of a finite size demonstrator apparatus. Results show that, for demonstrator apparatuses of moderately small sizes, a significant accuracy improvement in the determination of the size of a planet model can be achieved using the proposed method in comparison to using the formula from the standard transit method. The radiance distribution of the star model is found to be of crucial importance, as deviations from a Lambertian radiance distribution can lead to significantly different results.

Experimental Demonstration of Non-Volatile Boolean Logic With Field Configurable 1FeFET-1RRAM Technology

Experimental Demonstration of Non-Volatile Boolean Logic With Field Configurable 1FeFET-1RRAM Technology

Encoding control system for twin-field quantum key distribution

The Twin-Field Quantum Key Distribution (TF-QKD) protocol has the potential to realize secure key distribution over extremely long distances, which is an important technique for realizing a global quantum network. Compared to the conventional BB84 protocol, practical TF-QKD and its variant protocols require an accurate phase modulation to at least 16 different values with randomized encoding. In this work, we developed an encoding control system for TF-QKD. Optical pulses with five different intensities and 16 different phases can be modulated with a clock frequency of 100 MHz with a field programmable gate array based arbitrary waveform generator (AWG). With the assistance of DDR4 memory, waveforms exceeding 200 ms in length can be output simultaneously on 4 pairs of differential channels, making the random number pairing between two different encoding systems close to the expected ratio when using cyclic random numbers for experimental demonstration. The AWG boasts a long-term amplitude stability better than 0.03% and supports seamless concatenation and cyclic output of waveforms, demonstrating a strong and sustained performance in long-duration experiments. Sending-or-not-sending TF-QKD was demonstrated with the encoding control system, with a secure key rate of 1.33 × 10−5 per pulse under the total channel loss of ∼32 dB.

Experimental demonstration of plasmon–plasmon scattering paves the way for electromagnetic wave-based digital logic concept

We report the experimental demonstration of plasmon–plasmon scattering at room temperature in the inversion layer of a patterned metal–oxide–semiconductor structure. This fundamental result paves the way for the development of plasmon–plasmon scattering logic, a revolutionary digital logic concept based on the generation, propagation, and manipulation of plasmons in an electron fluid, which was previously theoretically projected to exhibit femtojoule power dissipations and femtosecond switching speeds, while not demanding expensive nanometer-scale silicon (Si) technology fabrication processes for its implementation.

Elucidating optimal nanohole structures for suppressing phonon transport in nanomeshes

Nanomeshes, often referred to as phononic crystals, have been extensively explored for their unique properties, including phonon coherence and ultralow thermal conductivity (κ). However, experimental demonstrations of phonon coherence are rare and indirect, often relying on comparison with numerical modeling. Notably, a significant aspect of phonon coherence, namely the disorder-induced reduction in κ observed in superlattices, has yet to be experimentally demonstrated. In this study, through atomistic modeling and spectral analysis, we systematically investigate and compare phonon transport behaviors in graphene nanomeshes, characterized by 1D line-like hole boundaries, and silicon nanomeshes, featuring 2D surface-like hole boundaries, while considering various forms of hole boundary roughness. Our findings highlight that to demonstrate a disorder-induced reduction in κ of nanomeshes, optimal conditions include low temperature, smooth and planar hole boundaries, and the utilization of thick films composed of 3D materials.