Quantum Information Processing最新文献

In this paper, a new scheme for asymmetric cyclic controlled teleportation of arbitrary three-dimensional unknown quantum states is proposed by performing three-dimensional Bell-state measurements and three-dimensional Hadamard transformation. The entangled state of thirteen-qutrit acts as the quantum channel to connect senders and receivers, which is constructed by a three-qutrit entangled state and five two-qutrit entangled states. In this scheme, Alice wants to transmit an arbitrary unknown single-qutrit state to Bob, at the same time, Bob wants to transmit an arbitrary unknown two-qutrit entangled state to Charlie and Charlie wants to transmit an arbitrary unknown three-qutrit entangled state to Alice under the control of the supervisor David. Participants can reconstruct the original states and make the scheme perfectly by performing appropriate unitary operation. Then, the scheme can be generalized to realize the asymmetric cyclic controlled quantum teleportation of N (N > 3) participants in the three-dimensional system, and come up with two universal schemes are determined by the parity of the participant. Furthermore, the scheme is investigated in two different noisy channels: amplitude-damping noise and phase-damping noise, and calculated the fidelities of the output states. It is demonstrated that the fidelities only depend on the coefficients of the initial state and the decoherence noisy rate. The security of the scheme is briefly analyzed and compares with the previous schemes in terms of efficiency. The proposed scheme contributes to advancing understanding of high-dimensional quantum teleportation.

We study the ground-state entanglement between two atoms in a two-dimensional isotropic harmonic trap. We consider a finite-range soft-core interaction that can be applied to simulate various atomic systems. We provide detailed results on the dependence of the correlations on the parameters of the system. Our investigations show that in the hardcore limit, the wave function can be approximated as the product of the radial and angular components regardless of the interaction range. This implies that the radial and angular correlations are independent of one another. However, correlations within the radial and angular components persist and are heavily influenced by the interaction range. The radial correlations are generally weaker than the angular correlations. When soft-core interactions are considered, the correlations exhibit more complex behavior.

Digital signatures play a vital role in data security as they provide authenticity and non-repudiation of digital data. Code-based digital signatures are in high demand as quantum computers are extremely effective at breaking widely used digital signatures. The Courtois–Finiasz–Sendrier (CFS) scheme is one of the most popular code-based digital signature schemes. However, it has some disadvantages, such as a large public key size and poor signing efficiency. To address this issue, we construct a digital signature scheme named ENR DigiSig (Ekta Narwal and Rupali Digital Signature) using polar codes with several characteristics such as small signature size, low signing time, and high signing efficiency. Here, the hash of a shorter length is used in a specific way; then, padding is done to the hash output so that the result can be decoded. For this study, we have selected a fixed polar code rate of 0.5 and a blocklength of (N=2^{n};nleqslant 4). According to the experimental results, more than 96% of the signatures are generated successfully.

We consider discrete time feedback aimed at reclaiming quantum information after a channel action. We compare Bayesian and Markovian strategies. We show that the former does not offer any advantage for qubit channels, while its superior performance can appear in higher-dimensional channels. This is witnessed by cases study for qutrit channels.

To be more realistic, this paper considers the pursuit of maximizing relative profits by firms, establishes a Cournot duopoly game model with quantum entanglement, and investigates how quantum entanglement influences decisions made by the firms. Following that, the Jacobi matrix and Jury criterion are used to examine the local stability of the Nash equilibrium. Additionally, the impact of various model parameters on system stability is investigated by implementing a numerical experiment. It has been found that limiting the adjustment speed and squeezing parameter to an appropriate range contributes to the long-term stability of the market. The coexistence of attractors is then fully investigated by means of the basin of attraction. The coexistence of attractors provides insights into the complexity and diversity of dynamic systems, shedding light on their nonlinear nature and sensitivity to initial conditions. Finally, the critical curve and the noninvertible map allow us to examine the global dynamics of the system.

Orthogonal frequency-division multiplexing (OFDM) is a crucial modulation method used in contemporary digital communication systems for its significant spectral efficiency, low latency, and robustness in challenging environments. This work examines the novel use of OFDM in quantum communication, an area that offers exceptional security and efficiency in information transfer using quantum mechanics principles. In the rapidly evolving field of quantum computing, understanding, and mitigating quantum bit errors is paramount. This paper presents a rigorous analysis of bit error rates (BER) in quantum circuits, focusing on the impact of the quantum Fourier transform and its inverse, contrasted against quantum circuits employing dynamic gate sequences. Our research methodology encompasses simulations over a diverse set of parameters, including varying qubit counts ranging from 2 to 8 and theta angles (15, 30, 45, and 60°), as well as random theta values, utilizing the advanced capabilities of the Qiskit framework. Our findings indicate that quantum OFDM substantially improves quantum communication, lowering errors and boosting security. The quantum model outperforms the reference model in BER, with further enhancements as qubits increase.

This paper presents a hybrid variational quantum algorithm that finds a random eigenvector of a unitary matrix with a known quantum circuit. The algorithm is based on the SWAP test on trial states generated by a parametrized quantum circuit. The eigenvector is described by a compact set of classical parameters that can be used to reproduce the found approximation to the eigenstate on demand. This variational eigenvector finder can be adapted to solve the generalized eigenvalue problem, to find the eigenvectors of normal matrices and to perform quantum principal component analysis on unknown input mixed states. These algorithms can all be run with low-depth quantum circuits, suitable for an efficient implementation on noisy intermediate-scale quantum computers and, with some restrictions, on linear optical systems. In full-scale quantum computers, where there might be optimization problems due to barren plateaus in larger systems, the proposed algorithms can be used as a primitive to boost known quantum algorithms. Limitations and potential applications are discussed.

Quantum error correction techniques are important for implementing fault-tolerant quantum computation, and topological quantum error correcting codes provide feasibility for implementing large-scale fault-tolerant quantum computation. Here, we propose a deep reinforcement learning framework for implementing quantum error correction algorithms for errors on heavy hexagonal codes. Specifically, we construct the double deep Q learning model with policy reuse method, so that the decoding agent does not have to explore the learning from scratch when dealing with new error syndrome, but instead reuses past policies, which can reduce the computational complexity. And the double deep Q network can avoid the problem of threshold being overestimated and get the true decoding threshold. Our experimental results show that the error correction accuracy of our decoder can reach 91.86%. Different thresholds are obtained according to the code distance, which is 0.0058 when the code distance is 3, 5, 7, and 0.0065 when the code distance is 5, 7, 9, both higher than that of the classical minimum weight perfect matching decoder. Compared to the threshold of the MWPM decoder under the depolarizing noise model, the threshold of our decoder is improved by 32.63%, which enables better fault-tolerant quantum computation.

A quantum conference key agreement (QCKA) protocol based on differential-phase-shift quantum key distribution is presented, which provides a common secret key for secure communication between more than two parties. In the proposed protocol, one party simultaneously broadcasts a weak coherent pulse train with {0, π} phases to multiple parties that measure the phase differences between adjacent pulses using a delay interferometer followed by photon detectors, and the transmitter and receivers share secret key bits from the coincident counts in the receivers. The system setup and operation are simpler than those of conventional QCKA schemes that use a multipartite quantum entanglement state. The key creation performance is evaluated by considering the eavesdropping probability. The results indicate that the proposed scheme offers better performance than the conventional entanglement-based QCKA system.

Uncertainty principle is one of the most fundamental features in quantum mechanics and plays a significant role in quantum information processing. We establish tighter summation form of the uncertainty relations based on metric-adjusted skew information via operator representation of observables, which improves the existing results. By employing the methodologies of sampling coordinates of observables, we also present tighter product form of the uncertainty relations. Detailed examples are given to illustrate the advantages of our uncertainty relations.