Quantum Information Processing最新文献

In the present work, we introduce some analytical bounds for the Ramos disentropy and Renyi-based Ramos disentropy of the Wigner function. We will prove that the Lambert–Tsallis function W_q with q = 2 effectively characterizes the quasi-probability of Fock states. Inequalities for Ramos disentropy and Renyi-based Ramos disentropy in phase plane compact domains are obtained. At last, we will show that the essential norm of the Ramos disentropy for positive Wigner states is finite and an upper limit for Renyi-based disentropy is established in space ({L}^{alpha }({mathbb{R}}^{d})).

This paper establishes a dynamic quantum Cournot game model incorporating an externality cost function, where participants aim to maximize relative profits and possess bounded rationality, updating their output for the next period using a gradient adjustment mechanism. Based on the established model, we analyze the existence and stability of quantum Nash equilibria and investigate the complex behavior of the system. The research results indicate that as the adjustment speed increases, the system’s stability decreases due to the emergence of Flip and Neimark–Sacker bifurcations. However, increasing the degree of quantum entanglement can delay the occurrence of bifurcation behavior. Furthermore, we find that when enterprises cannot control chaotic states by adjusting external cost parameters, they can transition the system from a chaotic to a stable state by altering product differentiation and quantum entanglement. Finally, numerical simulations validate the theoretical analysis and visually demonstrate complex dynamic characteristics, such as bifurcation diagrams, the maximum Lyapunov exponent, strange attractors, sensitivity to initial conditions, and chaos.

We propose a novel quantum voting protocol that utilizes superdense coding of four-particle entangled states. The protocol is simultaneously legitimate, anonymous, blind, verifiable and irreducible. In order to prevent malicious tampering of the public content, we introduce the distributed proof of work (PoW) consensus algorithm in blockchain as a database mechanism for voting participants. The voting protocol utilizes four-particle entangled states as a quantum resource to perform only single-particle operations, as well as GHZ basis measurements and (left{ | 0 rangle ,| 1rangle right} )-basis measurements. This means that our protocol can be successfully implemented using existing quantum information processing techniques. We conduct simulation experiments on the proposed voting protocol on the IBM Qiskit platform, and the results show that it is correct and feasible.

In the burgeoning field of quantum computing, the precise design and optimization of quantum pulses are essential for enhancing qubit operation fidelity. This study focuses on refining the pulse engineering techniques for superconducting qubits, employing a detailed analysis of square and Gaussian pulse envelopes under various approximation schemes. We evaluated the effects of coherent errors induced by naive pulse designs. We identified the sources of these errors in the Hamiltonian model’s approximation level. We mitigated these errors through adjustments to the external driving frequency and pulse durations, thus implementing a pulse scheme with stroboscopic error reduction. Our results demonstrate that these refined pulse strategies improve performance and reduce coherent errors. Moreover, the techniques developed herein are applicable across different quantum architectures, such as ion-trap, atomic, and photonic systems.

The present status of quantum computing is of the noisy intermediate-scale quantum (NISQ) era. In addition to the limited number of available qubits, NISQ devices generally possess two other physical constraints, quantum gate and interaction constraints. Those constraints should be satisfied in order for realizing a quantum circuit on an NISQ device. However, this often introduces extra CNOT gates into the circuit which harm the fidelity of the resulting circuit. Consequently, the number of extra CNOT gates needs to be reduced while compiling a quantum circuit onto an NISQ device. To this end, here, a solution that uses Q-learning (QL) is proposed by dividing physical synthesis of quantum circuits into qubit placement and routing. QL algorithms are designed for qubit placement and routing, respectively, by considering them as sequential decision-making problems. A physical synthesis method for quantum circuits is proposed by first using a QL algorithm to learn an optimally initial qubit mapping and then using another QL algorithm to learn an optimal routing scheme. A number of quantum circuits are compiled onto quantum architectures provided by IBM and grid architectures by using the proposed synthesis method. Compared to several methods for physical synthesis of quantum circuits, the proposed synthesis method can reduce the number of extra CNOT gates or the depth of the resulted physical quantum circuit in many cases. In a few cases, the QL algorithm designed for qubit placement can find an initial qubit mapping that makes all gates in a circuit being executed on a quantum architecture provided by IBM.

In this paper, we have investigated the behavioral features of quantum-memory-assisted entropic uncertainty (QMA-EU), the lower bound of QMA-EU, and steered quantum coherence (SQC) in double quantum dots system hosting a single electron spin in the presence of external magnetic field and Rashba spin-orbit interaction (SOI) under thermal equilibrium and decoherence conditions, respectively. We find that although the nonlocality and nonclassicality quantified by QMA-EU and SQC deteriorates even disappears as thermal fluctuation dominates the system at higher temperature, the Rashba SOI and tunneling effects between the two quantum dots can be used effectively to enhance the thermal performance of quantumness, which is to enhance the system’s SQC and reduce QMA-EU. However, if the decoherence is taken into account, the Rashba SOI accelerates evolution oscillation frequency of QMA-EU and SQC and even makes the oscillation of them smooth. Furthermore, we reveal that the behavior of SQC with respect to the Rashba SOI and tunneling effects is not strictly opposite to that of QMA-EU.

E2 algorithm is one of the 15 candidate algorithms in the first round of AES collection. In this paper, taking E2-128 as an example, the quantum security analysis on E2 algorithm is proposed for the first time in quantum chosen-plaintext attack setting. First, a polynomial-time distinguisher on 4-round E2-128 is constructed with (2^{12.1}) quantum queries by taking the properties of the internal round function into consideration. Then, by extending the distinguisher 2 rounds backward, a 6-round quantum key recovery attack is achieved with the help of Grover-meet-Simon algorithm, whose time complexities gain a factor of (2^{76}), where the subkey length that can be recovered is 152 bits with the occupation of 560 qubits. Furthermore, when attacking (r>6) rounds, (152+(r-6)times 128)-bit subkey needs to be guessed in time (2^{76+(r-6)times 64}), which is (frac{1}{2^{52}}) of Grover’s quantum brute force search. Finally, we present a quantum attack against E2-128 with ({2^{88.1}}) quantum queries by taking initial transformation and terminal transformation into consideration. The result shows that the time complexity of the quantum attack is significantly reduced, and E2 algorithm is safe enough to resist quantum attack.

We present a scheme to generate nonreciprocal entanglement and asymmetric steering between an atomic ensemble and a magnon based on Kerr nonlinearity of magnon in an yttrium iron garnet sphere. In particular, a cavity optomagnonic system is under our consideration, where the optical cavity couples with an ensemble of N two-level atoms, and meanwhile nonlinearly interacts with the magnon mode via optomagnonic coupling. The results demonstrate that the steady-state macroscopic quantum correlations including magnon-atomic ensemble entanglement and Einstein–Podolsky–Rosen steering could be obtained via strongly driving the cavity mode. More importantly, tuning the direction of the static magnetic field leads to a positive or negative magnon Kerr coefficient, which leads to a corresponding shift in magnon frequency and thus induces the nonreciprocity of entanglement. Furthermore, the one-way steering between magnon and atomic ensemble is also shown via properly choosing the coupling strengths and effective Kerr parameters. Our work could have potential applications in the preparation of macroscopic quantum states and be applied to construct long-distance quantum networks.

The lottery business is a form of gambling activity operated by authority agencies. Due to the substantial economic interests, its security and fairness become the core elements of industry development. To maintain the trust of participants and ensure fair competition, blockchain technology has been widely applied in the lottery field due to the characteristics of decentralization, transparency, and immutability. However, with the rapid advancement of quantum computing, the security of traditional blockchain technology is challenged largely. To tackle this issue, a novel consensus mechanism which can resist quantum attacks is first proposed, based on a self-tallying quantum voting protocol. Then, a quantum circuit is designed, which can encode n-bit binary information into the relative phase of a quantum state and entangle the blocks by means of controlled-Z (CZ) gate, forming a quantum blockchain structure with timestamps. Finally, utilizing the designed quantum blockchain, a new type of lottery protocol is constructed. The proposed protocol meets the requirements of decentralization, unforgeability, verifiability, and quantum attack resistance. Compared to existing lottery protocols, it can support an arbitrary number of players, and only one communication is required for the ticket purchase process of each player, making it suitable for most of lottery game scenarios.

In this paper, we provide two new methods of constructing entanglement-assisted quantum error-correcting (EAQEC) codes by using the LCD codes decomposition of linear codes. We first construct a class of maximal entanglement EAQEC maximum distance separable codes via the LCD codes decomposition of generalized Reed–Solomon (GRS) codes over finite fields (mathbb {F}_{2^m}). We then construct two classes of maximal entanglement EAQEC codes based on the LCD codes decomposition of matrix-product codes related to cyclic codes over finite fields (mathbb {F}_{q}). In addition, we construct EAQEC codes with better parameters than the ones available in the literature.