Advanced quantum technologies最新文献

The cardinality of the private set allows multiple parties to jointly compute the cardinality of the intersection and union without revealing their respective private sets. It plays an important role in data mining and data analysis to protect privacy. However, existing studies only focus on computing the cardinality of the intersection or union of private sets. To extend its application in various scenes, a private-set intersection and union mixed cardinality protocol are proposed for any tripartite based on Bell states for the first time. During the protocol, participants are supposed to be semi-quantum to reduce the consumption of quantum resources and improve the realizability of the protocol. Furthermore, correctness and security analysis show that the protocol can withstand internal and external attacks. Additionally, the IBM Quantum Simulator (IBMQS) is also applied to illustrate the fundamentals of the protocol and verify the availability of the protocol. The results are expected have positive effects on the further development of secure multiparty computation.

An extended Su–Schrieffer–Heeger (SSH) model consisting of an SSH chain with an embedded quantum ring (QR) is investigated. In the case of two SSH chains with a symmetric distribution with respect to QR, by calculating the real-space winding number and energy spectrum, the hopping amplitude-induced topological phase is discovered. The probability distributions of gap states and the relationship between energy and magnetic flux prove the existence of the Aharonov–Bohm effect in the QR. Moreover, in the case of asymmetric distribution, the model possesses a zero-energy mode within the energy gap, and it is found that it can realize quantum state transfer. By adjusting the connection site between the right SSH chain and QR, the direction of the output port can be flexibly engineered. Furthermore, it is shown that high-fidelity quantum state transfer can still be achieved with the increasing of the system size. The tunable quantum state transfer based on the zero-energy mode can be equivalent to a topological tunable directional switch with properties of non-directional transfer. This work provides an approach for studying topological phase transition and tunable topological devices in an SSH chain with an embedded QR.

The non-Hermitian singularity control of multimode entanglement in the energy-level cascaded four-wave mixing system within a single atomic vapor is of great significance and importance. In this study, a non-Hermiticity system by means of quasi-quantization of energy-band based on non-Hermiticity systems is constructed. By employing atomic coherence in the non-Hermiticity system, high-dimensional quantized photon correlations underdressed field-induced parity-time (PT) symmetry and symmetry breaking through the quantization of energy levels are studied. Such a phenomenon happens at microscopic (nanoscale) when the eigenvalues of dressed energy-level and multimode entanglement are considered for both real and imaginary parts symmetry breaking. Double dressing effect is observed with more coherent channels and larger information capacity than single dressing in the energy-level cascaded four-wave mixing system. The study found that the splitting of the real part is larger than an imaginary part in a second-order system, and the imaginary part splitting is also greater than the real part splitting in a third-order system. The real part (in phase) is constructive dressing quantization, and the imaginary (out of phase) is destructive dressing quantization. Exceptional points (EP points) can be used to enhance sensitivity detection of entanglement quantum state.

There is a growing interest in harnessing the potential of the Rydberg-atom system to address complex combinatorial optimization challenges. Here an experimental demonstration of how the quadratic unconstrained binary optimization (QUBO) problem can be effectively addressed using Rydberg-atom graphs is presented. The Rydberg-atom graphs are configurations of neutral atoms organized into mathematical graphs, facilitated by programmable optical tweezers, and designed to exhibit many-body ground states that correspond to the maximum independent set (MIS) of their respective graphs. Four elementary Rydberg-atom subgraph components are developed, not only to eliminate the need of local control but also to be robust against interatomic distance errors, while serving as the building blocks sufficient for formulating generic QUBO graphs. To validate the feasibility of the approach, a series of Rydberg-atom experiments selected to demonstrate proof-of-concept operations of these building blocks are conducted. These experiments illustrate how these components can be used to programmatically encode the QUBO problems to Rydberg-atom graphs and, by measuring their many-body ground states, how their QUBO solutions are determined subsequently.

This study proposes compact, highly sensitive, and stable diamond quantum sensors for a wide range of applications, including biomedical and energy electronics. For enhanced sensitivity and alignment precision within the objective field, a high-quality, (111)-oriented ¹²C-enriched chemical vapor deposition (CVD) diamond, featuring a nitrogen-vacancy (NV) axis in the (111) direction, is employed as the sensor. To increase the fluorescence collection efficiency, the laser beam is irradiated from the side surface of the CVD diamond, and fluorescence is detected using a compound parabolic concentrator (CPC) lens. The floor noise level of the magnetic field signal is 44 pT/Hz^0.5. An Allan deviation of 1.2 pT over 1000 s of averaging demonstrates stability. This is attributable to the integration of a balancing circuit to cancel out laser noise, alongside mechanisms to compensate for temperature fluctuations and a copper housing to shield against electromagnetic field noise.

Satellite-to-ground quantum communication constitutes the cornerstone of the global quantum network, heralding the advent of the future of quantum information. Continuous-variable quantum key distribution is a strong candidate for the space-ground quantum communication due to its simplicity, stability, and ease of implementation, especially for the robustness of space background light noise. Recently, the discrete-modulated continuous-variable protocol has garnered increased attention, owing to its lower implementation requirements, acceptable security key rate, and pronounced compatibility with extant infrastructures. Here, key rates are derived for discrete-modulated continuous-variable quantum key distribution protocols in free-space channel environments across various conditions through numerical simulation, revealing the viability of its application in satellite-to-ground communication.

Employing the constructs of density functional theory (DFT) and the Nonequilibrium Green's Function (NEGF), the investigation extensively explores the electronic and transport properties of zigzag graphene nanoribbons (ZGNRs) doped with vanadium (V). Notably, this inquiry unveils that strategic doping can transform V-doped ZGNRs into spintronic nanodevices with distinctive transport attributes. Initially, the simulations showcase remarkably high spin-filtering efficiencies (SFEs) at certain bias voltages. Furthermore, a giant magnetoresistance (GMR) peaking at 6.87 $�\times$ 10$�{}^3$ is detected. In conclusion, the examination discerns a spin rectifier that exhibits a significant rectification ratio (RR) of 9.62 $�\times$ 10$�{}^2$. This research delineates a viable trajectory for the refinement of high-performance spintronics in ZGNRs via vanadium doping. The implications of this study indicate that the model harbors considerable promise for application in miniature spintronic devices.

Recent work has proposed solving the k-means clustering problem on quantum computers via the Quantum Approximate Optimization Algorithm (QAOA) and coreset techniques. Although the current method demonstrates the possibility of quantum k-means clustering, it does not ensure high accuracy and consistency across a wide range of datasets. The existing coreset techniques are designed for classical algorithms, and there is no quantum-tailored coreset technique designed to boost the accuracy of quantum algorithms. This study proposes solving the k-means clustering problem with the variational quantum eigensolver (VQE) and a customized coreset method, the Contour coreset, which is formulated with a specific focus on quantum algorithms. Extensive simulations with synthetic and real-life data demonstrated that the VQE+Contour Coreset approach outperforms existing QAOA+Coreset k-means clustering approaches with higher accuracy and lower standard deviation. This research demonstrates that quantum-tailored coreset techniques can remarkably boost the performance of quantum algorithms compared to generic off-the-shelf coreset techniques.

Recently, a groundbreaking advancement known as multimode photon blockade (MPB) is proposed by S. Chakram et al. [Nature. Phys. 18, 879-884 (2022)], showcasing its ability to generate multimode W states. Inspired by their work, in this paper, an interesting method is proposed to investigate MPB by engineering the eigenstates of the system Hamiltonian, which is defined as the reverse design method. It is demonstrated that an entangled state is created with a certain probability by sharing a single photon between two coupled Kerr-nonlinear cavities. This entangled state in the two-coupled cavities blocks the creation of the subsequent photons. The system is in a superposition of only the entangled state and the vacuum state. And the photon blockade (PB) exists in two cavities simultaneously. The reversed design method can also be utilized to study MPB in three coupled cavities with Kerr nonlinearities by creating a three-qubit W state.

Quantum secret sharing has many important applications in quantum communication and secure multiparty computing. In this work, a novel measurement-device-independent protocol for three-party quantum secret sharing is put forward, in which the dealer and two sharers are required to prepare Greenberger-Horne-Zeilinger states and single particles, respectively, but they only need to perform single-particle measurement. As a result, this protocol is feasible in experiments by using current technologies. More importantly, it can extend the spatial distance among three participants for quantum state transmissions at least 15.47% compared to the previous protocols.