Deterministic Generation Research Articles

Improved Heralded Single-Photon Source with a Photon-Number-Resolving Superconducting Nanowire Detector

Deterministic generation of single photons is essential for many quantum information technologies. A bulk optical nonlinearity emitting a photon pair, where the measurement of one of the photons heralds the presence of the other, is commonly used with the caveat that the single-photon emission rate is constrained due to a trade-off between multiphoton events and pair emission rate. Using an efficient and low noise photon-number-resolving superconducting nanowire detector we herald, in real time, a single photon at telecommunication wavelength. We perform a second-order photon correlation ${g}^{2}(0)$ measurement of the signal mode conditioned on the measured photon number of the idler mode for various pump powers and demonstrate an improvement of a heralded single-photon source. We develop an analytical model using a phase-space formalism that encompasses all multiphoton effects and relevant imperfections, such as loss and multiple Schmidt modes. We perform a maximum-likelihood fit to test the agreement of the model to the data and extract the best-fit mean photon number $\ensuremath{\mu}$ of the pair source for each pump power. A maximum reduction of $0.118\ifmmode\pm\else\textpm\fi{}0.012$ in the photon ${g}^{2}(0)$ correlation function at $\ensuremath{\mu}=0.327\ifmmode\pm\else\textpm\fi{}0.007$ is obtained, indicating a strong suppression of multiphoton emissions. For a fixed ${g}^{2}(0)=7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$, we increase the single pair generation probability by 25%. Our experiment, built using fiber-coupled and off-the-shelf components, delineates a path to engineering ideal sources of single photons.

A novel deterministic substitution box generator over elliptic curves for real-time applications

Recently, highly dynamic substitution box (S-box) generators are widely used in cryptosystems to improve the security against modern computational attacks. However, generating S-boxes is computationally costly, and frequently generating them slows down the encryption process and hence limits the encryption throughput. This fact necessitates developing new S-box generators that can provide optimal security with minimum computation cost. We propose a novel S-box generator based on a deterministic algorithm over elliptic curves to generate highly dynamic and secure S-boxes with low computation cost. Experimental results show that our generator is i times, i∈[6.720,1.3×105] faster than the fastest available S-box generator to generate S-boxes of an input size 2m,m=4,6,8,10,12,14,16 over large ECs. This fact allows us to attain significantly higher throughput as compared to the state-of-the-art schemes. Furthermore, our generator can generate highly dynamic, key-sensitive, and cryptographically secure S-boxes. As a sample application, we used our generator in an image encryption scheme. Experimental results reveal that our encryption scheme has high resistance against differential and statistical attacks, and key attacks. Furthermore, with the new S-box generator, the running time of the modified scheme reduced by two orders of magnitude.

Self-regulating soliton switching waves in microresonators

Dissipative soliton Kerr frequency combs in microresonators have recently been demonstrated with the self-injection locking process. They have the advantage of turnkey deterministic comb generation and simplifying dark soliton generation in the normal dispersion regime. Here, the formation process of dark pulses triggered by self-injection locking is studied by regarding them as a pair of domain walls that connect domains having different intracavity powers. The self-injection locking mechanism allows the domain walls to self-regulate their position so that a wide range of dark comb states can be accessed, and the duty cycle is controlled by the feedback phase. Direct imaging of the dark pulse shape using the electro-optic sampling technique is used to verify the theory. The results provide new physical insights as well as a new operational modality for this important class of nonlinear waves.

Blockchain-based trust mechanism for digital twin empowered Industrial Internet of Things

Emerging technologies such as blockchain and digital twins are essential for the rapid development and employment in Industry 5.0 revolution. With the growing number of industrial IoT nodes, optimizing the network and availing of limited resources to enable secure transmission is difficult. A digital twin is the virtual representation of a physical device that completely depends on sensor data for the critical decision-making simulation process. To this end, we combine a blockchain-based distributed network with a digital twin for the Industrial Internet of Things (IIoT) applications. This paper proposes a blockchain-based Proof of Authority (PoA) trust mechanism to provide high-quality services such as security and data privacy in IIoT. Furthermore, to enhance the authority of decentralized digital twin combined blockchain networks, we introduce a Deterministic Pseudo-Random Generation (DPRG) to generate a genesis block. To evaluate the trustworthiness of the proposed system, we simulate the blockchain network with a digital twin using IIoT sensor nodes. The simulation result shows that the PoA-based authority master nodes can reduce energy consumption and enhance data security.

Compact source for quadripartite deterministically entangled optical fields

Since entangled multiple optical fields were identified as the building blocks of quantum networks, the quadripartite entangled optical fields have been produced by using four degenerate optical parametric amplifiers or two nondegenerate optical parametric amplifiers (NOPAs). However, realizing an efficient and compact source for multiple quantum users has remained an outstanding challenge, hindering their practical applications. Here, we proposed a compact and feasible scheme to deterministically entangle four spatially separated optical fields, employing only a single NOPA. Accordingly, two-sided output NOPA-based optical fields were coupled on a beam splitter network to form the quadripartite entangled state, causing the deterministic generation of both the Greenberger–Horne–Zeilinger (GHZ) and the linear cluster states in this compact entanglement source. We also obtained the optimal experimental parameters based on the simulation results, thereby providing a direct reference for experimental implementation. Our findings propose that the resultant GHZ and linear cluster states can be potentially applied in quantum-enhanced information science, specifically in quantum secret sharing, controlled quantum teleportation networks, and quantum-entangled atomic ensemble networks.

Deterministic generation of entanglement states between Silicon-Vacancy centers via acoustic modes.

We propose a scheme to entangle Silicon-Vacancy (SiV) centers embedded in a diamond acoustic waveguide. These SiV centers interact with acoustic modes of the waveguide via strain-induced coupling. Through Morris-Shore transformation, the Hilbert space of this hybrid quantum system can be factorized into a closed subspace in which we can deterministically realize the symmetrical Dicke states between distant SiV centers with high fidelity. In addition, the generation of entangled Dicke states can be controlled by manipulating the strength and frequency of the driving field applied on SiV centers. This protocol provides a promising way to prepare multipartite entanglement in spin-phonon hybrid systems and could have broad applications for future quantum technologies.

Transient and Fast Generation of Bose-Einstein-Condensate Macroscopic Quantum Superposition States via Impurity Catalysing

Macroscopic quantum superposition is an important embodiment of the core of the quantum theory. The engineering of macroscopic quantum superposition states is the key to quantum communication and quantum computation. Thus, we present a theoretical proposal to engineer macroscopic quantum superposition (MQS) states of a Bose-Einstein condensate (BEC) via impurity atoms. We firstly propose a deterministic generation scheme of transient multi-component MQS states of the BEC via impurity catalysing. It is found that the structure of the generated transient multi-component MQS states can be manipulated by the impurity number parity. Then, we illustrate the influence of impurity number parity on MQS states through three aspects: generation of approximately orthogonal continuous-variable cat states, manipulation of non-classicality in phase space, and switching of non-classical degree of BEC states. The influence of the BEC decoherence on the generation of MQS states is discussed by the fidelity between actually generated states and target states. Finally, the results show that the high-fidelity multi-component MQS states of the BEC can be fast generated by increasing the coherent interaction strength between impurities and the BEC in an open system.

Deterministic Entanglement of Large-Scale Hermite-Gaussian Modes

Continuous-variable (CV) entanglement constitutes a powerful approach to deterministic quantum information protocols. Improving the scale of entanglement is of vital importance for enhancing the information capacity of quantum information protocols. Here we demonstrate the deterministic generation of CV entanglement of large-scale Hermite-Gaussian (HG) modes from the four-wave mixing (FWM) process in an atomic vapor. In our experiment, 56 pairs of entangled HG modes are deterministically and simultaneously generated from the FWM process, which increases the number of entangled spatial mode pairs in the CV system. Meanwhile, we experimentally verify the existence of CV entanglement between the evolution process from HG mode to Laguerre-Gaussian mode. Our results shed light on constructing high-capacity CV quantum information protocols and provide a promising platform to study CV entanglement.

Deterministic generation of multiple topological corner states based on an extremely expanded coupling condition

Photonic higher-order topological insulators (HOTIs) based on kagome photonic crystals (PCs) possess rich physics of corner states for the unignorable long-range interactions. Theoretically, there should be multiple corner states, i.e., type I, antisymmetric type II, and symmetric type II corner states, in the kagome PCs. However, for the generation of some corner states, especially the symmetric type II corner states, it is necessary to obtain a large ratio of intercell coupling to intracell coupling, which makes the spacing between dielectric units very small and difficult to achieve experimentally. Here, we propose a scheme for the deterministic generation of multiple topological corner states based on an extremely expanded coupling condition. We construct an equilateral triangular cavity that consists of nontrivial unit cells in triangular PCs. All three topological corner states can exist robustly in the triangular cavity with large dielectric unit spacing. By establishing a tight-binding model for the nontrivial unit cell, we reveal that the extremely expanded coupling condition is the core physical mechanism for the deterministic generation of multiple corner states. The study provides a simple and deterministic method to generate multiple topological corner states, which has great potential in topological robust cavity, optical switches and lasers in integrated photonics on a silicon-on-insulator (SOI) or III-V active semiconductor platform.

All-Photonic Architecture for Scalable Quantum Computing with Greenberger-Horne-Zeilinger States

Linear optical quantum computing is beset by the lack of deterministic entangling operations besides photon loss. Motivated by advancements at the experimental front in deterministic generation of various kinds of multiphoton entangled states, we propose an architecture for linear-optical quantum computing that harnesses the availability of three-photon Greenberger-Horne-Zeilinger (GHZ) states. Our architecture and its subvariants use polarized photons in GHZ states, polarization beam splitters, delay lines, optical switches and on-off detectors. We concatenate topological quantum error correction code with three-qubit repetition codes and estimate that our architecture can tolerate remarkably high photon-loss rate of $11.5 \%$; this makes a drastic change that is at least an order higher than those of known proposals. Further, considering three-photon GHZ states as resources, we estimate the resource overheads to perform gate operations with an accuracy of $10^{-6}~(10^{-15})$ to be $2.0\times10^6~(5.6\times10^7)$. Compared to other all-photonic schemes, our architecture is also resource-efficient. In addition, the resource overhead can be even further improved if larger GHZ states are available. Given its striking enhancement in the photon loss threshold and the recent progress in generating multiphoton entanglement, our scheme will make scalable photonic quantum computing a step closer to reality.

Deterministic generation of entanglement in a quantum network by coherent absorption of a single photon

Advanced quantum information protocols rely on the operation of multinodal quantum networks where entanglement is distributed across the nodes. Existing protocols of entanglement generation are probabilistic, with the efficiency dropping exponentially with the size of the system. We formulate an approach for the deterministic generation of entangled states of a multinodal quantum network of arbitrary size by coupling a single photon standing wave with the nodes of the network. We show experimentally how this can be implemented in a simple binodal system. Since this approach relies on collective excitation of the network---not on local interaction with individual nodes---it allows generation of entanglement with unitary efficiency, independent of the size and the nature of the network.

Deterministic generation of large-scale hyperentanglement in three degrees of freedom

Entanglement serves as a fundamental resource for quantum information protocols, and hyperentanglement has received an increasing amount of attention for its high-capacity characteristic. Increasing the scale of hyperentanglement, i.e., the number of modes in a hyperentangled system, is crucial for enhancing its capability in quantum information processing. Here, we demonstrate the generation of large-scale continuous-variable (CV) hyperentanglement in three degrees of freedom (DOFs), including azimuthal and radial indices of Laguerre–Gaussian (LG) modes and frequency. In our experiment, 216 pairs of hyperentangled modes are deterministically generated from the four-wave mixing process in an atomic vapor. In addition, we show that the entanglement between coherent LG superposition modes denoted by both azimuthal and radial quantum numbers can also be generated from this system. Such large-scale CV hyperentanglement in three DOFs presents an efficient scheme to significantly increase the information capacity of the CV system. Our results provide a new platform for studying CV quantum information and open the avenue for constructing high-capacity parallel and multiple-DOF CV quantum information protocols.

Long-distance distribution of qubit-qubit entanglement using Gaussian-correlated photonic beams

We investigate the deterministic generation and distribution of entanglement in large quantum networks by driving distant qubits with the output fields of a nondegenerate parametric amplifier. In this setting, the amplifier produces a continuous Gaussian two-mode squeezed state, which acts as a quantum-correlated reservoir for the qubits and relaxes them into a highly entangled steady state. Here we are interested in the maximal amount of entanglement and the optimal entanglement generation rates that can be achieved with this scheme under realistic conditions taking, in particular, the finite amplifier bandwidth, waveguide losses, and propagation delays into account. By combining exact numerical simulations of the full network with approximate analytic results, we predict the optimal working point for the amplifier and the corresponding qubit-qubit entanglement under various conditions. Our findings show that this passive conversion of Gaussian into discrete-variable entanglement offers a robust and experimentally very attractive approach for operating large optical, microwave, or hybrid quantum networks, for which efficient parametric amplifiers are currently developed.

On-Demand Source of Dual-Rail Photon Pairs Based on Chiral Interaction in a Nanophotonic Waveguide

Entanglement is the fuel of advanced quantum technology, enabling, e.g., measurement-based quantum computing and loss-tolerant encoding of quantum information. In photonics, entanglement has traditionally been generated probabilistically, requiring massive multiplexing for scaling up to many photons. An alternative approach utilizing quantum emitters in nanophotonic devices can realize deterministic generation of entangled photons. However, such sources generate polarization entanglement that is incompatible with spatial dual-rail qubit encoding employed in scalable photonic quantum-computing platforms utilizing integrated circuits. Here we propose and experimentally realize an on-demand source of dual-rail photon pairs using a quantum dot in a planar nanophotonic waveguide. The source exploits the cascaded decay of a biexciton state and chiral light-matter coupling to achieve deterministic generation of spatial dual-rail Bell pairs with the amount of entanglement determined by the chirality. The operational principle can readily be extended to multiphoton entanglement generation required for efficient preparation of resource states for photonic quantum computing.Received 17 January 2022Revised 22 May 2022Accepted 8 June 2022DOI:https://doi.org/10.1103/PRXQuantum.3.020363Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasPhotonic crystalsPhotonicsQuantum communicationQuantum correlations in quantum informationQuantum entanglementSingle photon sourcesPhysical SystemsQuantum dotsWaveguidesPropertiesChiral symmetryAtomic, Molecular & OpticalQuantum Information

Nonlinear co-generation of graphene plasmons for optoelectronic logic operations

Surface plasmons in graphene provide a compelling strategy for advanced photonic technologies thanks to their tight confinement, fast response and tunability. Recent advances in the field of all-optical generation of graphene’s plasmons in planar waveguides offer a promising method for high-speed signal processing in nanoscale integrated optoelectronic devices. Here, we use two counter propagating frequency combs with temporally synchronized pulses to demonstrate deterministic all-optical generation and electrical control of multiple plasmon polaritons, excited via difference frequency generation (DFG). Electrical tuning of a hybrid graphene-fibre device offers a precise control over the DFG phase-matching, leading to tunable responses of the graphene’s plasmons at different frequencies across a broadband (0 ~ 50 THz) and provides a powerful tool for high-speed logic operations. Our results offer insights for plasmonics on hybrid photonic devices based on layered materials and pave the way to high-speed integrated optoelectronic computing circuits.

Dual-mode microresonators as straightforward access to octave-spanning dissipative Kerr solitons

The Kerr soliton frequency comb is a revolutionary compact ruler of coherent light that allows applications from precision metrology to quantum information technology. The universal, reliable, and low-cost soliton microcomb source is key to these applications. As a development and extension of the direct creation of a soliton microcomb with the dual-mode scheme in an aluminum nitride microresonator, this paper thoroughly presents the design strategy to reliably attain such dual-modes in the silicon nitride (Si3N4) platform, separated by ∼10 GHz, which stabilizes soliton formation without using additional auxiliary laser or RF components. We demonstrate the deterministic generation of the refined single-solitons that span 1.5-octaves, i.e., near 200 THz, via adiabatic pump wavelength tuning. The ultra-wide soliton existence range up to 17 GHz not only suggests the robustness of the system but will also extend the applications of soliton combs. Moreover, the proposed scheme is found to easily give rise to multi-solitons as well as the soliton crystals featuring enhanced repetition rate (2 and 3 THz) and conversion efficiency greater than 10%. We also show the effective thermal tuning of mode separation to increase the possibility to access the single-soliton state. Our results are crucial for the chip-scale self-referenced frequency combs with a simplified configuration.

Time-Varying Pseudorandom Disturbed Pattern Generation Algorithm for Track Circuit Equipment Testing.

To improve the test accuracy and fault coverage of high-speed railway-related equipment boards, a time-varying pseudorandom disturbance algorithm based on the automatic test pattern generation technology in chip testing is proposed. The algorithm combines the pseudorandom pattern generation algorithm with the deterministic pattern generation D algorithm. The existing pseudorandom number generation method usually requires random seeds to generate a series of pseudorandom numbers. In this algorithm, the system timer is used as the random seed to design a pseudorandom pattern generation method of time-varying seed to improve the randomness of pseudorandom pattern generation. In addition, in combination with the D algorithm, this work proposes a new switching logic between two algorithms by counting invalid pattern proportions. When the algorithm is applied to track a circuit netlist, the fault coverage can reach near 100%. However, the large-scale circuit fault coverage cannot easily reach 100%. The test results for the standard circuits of different sizes show that at the same time, compared with the independent pattern generation methods, the proposed algorithm can improve fault coverage by more than 50% and 30% and significantly improve the pattern generation efficiency. Therefore, it can be used perfectly in the subsequent construction of high-speed railway equipment test platforms.

Deterministic Generation and Guided Motion of Magnetic Skyrmions by Focused He+-Ion Irradiation.

Magnetic skyrmions are quasiparticles with nontrivial topology, envisioned to play a key role in next-generation data technology while simultaneously attracting fundamental research interest due to their emerging topological charge. In chiral magnetic multilayers, current-generated spin-orbit torques or ultrafast laser excitation can be used to nucleate isolated skyrmions on a picosecond time scale. Both methods, however, produce randomly arranged skyrmions, which inherently limits the precision on the location at which the skyrmions are nucleated. Here, we show that nanopatterning of the anisotropy landscape with a He+-ion beam creates well-defined skyrmion nucleation sites, thereby transforming the skyrmion localization into a deterministic process. This approach allows control of individual skyrmion nucleation as well as guided skyrmion motion with nanometer-scale precision, which is pivotal for both future fundamental studies of skyrmion dynamics and applications.

Numerical Optimization of a Nanophotonic Cavity by Machine Learning for Near-Unity Photon Indistinguishability at Room Temperature.

Room-temperature (RT), on-chip deterministic generation of indistinguishable photons coupled to photonic integrated circuits is key for quantum photonic applications. Nevertheless, high indistinguishability (I) at RT is difficult to obtain due to the intrinsic dephasing of most deterministic single-photon sources (SPS). Here, we present a numerical demonstration of the design and optimization of a hybrid slot-Bragg nanophotonic cavity that achieves a theoretical near-unity I and a high coupling efficiency (β) at RT for a variety of single-photon emitters. Our numerical simulations predict modal volumes in the order of 10–3(λ/2n)3, allowing for strong coupling of quantum photonic emitters that can be heterogeneously integrated. We show that high I and β should be possible by fine-tuning the quality factor (Q) depending on the intrinsic properties of the single-photon emitter. Furthermore, we perform a machine learning optimization based on the combination of a deep neural network and a genetic algorithm (GA) to further decrease the modal volume by almost 3 times while relaxing the tight dimensions of the slot width required for strong coupling. The optimized device has a slot width of 20 nm. The design requires fabrication resolution in the limit of the current state-of-the-art technology. Also, the condition for high I and β requires a positioning accuracy of the quantum emitter at the nanometer level. Although the proposal is not a scalable technology, it can be suitable for experimental demonstration of single-photon operation.

Dynamics of cavity soliton driven by chirped optical pulses in Kerr resonators

Recent researches have demonstrated that pulsed driving is an effective method to increase the temporal overlap between cavity soliton (CS) and pump field, thereby increasing the pump-to-comb conversion efficiency. The amplitude-modulated inhomogeneity of the background wave causes the solitons to drift toward edges of the driving pulse. To eliminate the multiple temporal trapping positions, induced by the spontaneous symmetry breaking, we propose the chirped pulse driving for deterministic single soliton generation. We theoretically explain the physical mechanism of the chirp pulse driving, as the combination of amplitude and phase modulation. Our numerical simulations demonstrate the chirp is responsible for the single soliton generation. A detailed investigation for dynamics of CSs sustained by chirped pulses, shows the recovery of spontaneous symmetry breaking. In addition, the desynchronized chirped pulse driving is also considered here. Considering a weak chirp parameter, the desynchronization-dependent trapping position diagram is divided into multiple areas including two CSs, a single CS, two oscillating CSs, and no CS. With a sufficient chirp parameter considered, the trapping position curve becomes a monotonous function of the desynchronized drift velocity, which indicates deterministic single soliton generation.Graphic