Quantum Information Processing最新文献

Quantum audio processing is of great significance for artificial intelligence-driven audio recognition technology. To address traditional deep learning methods’ low efficiency and insufficient temporal modeling capabilities in audio data processing, this paper proposes a quantum time-series encoding (QTSE) method and a quantum audio neural network (QANN). The QTSE method leverages entangled qubit sequences to efficiently encode audio data into quantum states while preserving essential features. Building on QTSE, a quantum audio neural network is further developed and applied to audio recognition and classification tasks through quantum circuit parameter optimization. Experimental results on the GTZAN dataset show that the proposed method achieves a classification accuracy of 75% under limited qubit conditions, outperforming traditional amplitude and angle encoding schemes. Furthermore, the proposed QANN architecture is inherently parameter-efficient, utilizing only 33 trainable parameters, a quantity substantially smaller than classical deep learning counterparts typically used for similar audio classification tasks. This research provides a new pathway for building efficient quantum audio processing technology and demonstrates broad application potential in quantum machine learning.

We study particle and energy transport in an open quantum system consisting of a three-harmonic oscillator chain coupled to thermal baths at different temperatures placed at the ends of the chain. We consider the exact dynamics of the open chain and its so-called local and global Markovian approximations. By comparing them, we show that, while all three yield a divergence-like continuity equation for the probability flow, the energy flow exhibits instead a distinct behavior. The exact dynamics and the local one preserve a standard divergence form for the energy transport, whereas the global open dynamics, due to the rotating wave approximation (RWA), introduces non-divergence sink/source terms. These terms also affect the continuity equation in the case of a master equation obtained through a time-coarse-graining method whereby RWA is avoided through a time-zoom parameter (Delta t). In such a scenario, sink and source contributions are always present for each (Delta t>0). While in the limit (Delta trightarrow +infty ) one recovers the global dissipative dynamics, sink and source terms instead vanish when (Delta trightarrow 0), restoring the divergence structure of the exact dynamics. Our results underscore how the choice of the dissipative Markovian approximation to an open system dynamics critically influences the energy transport descriptions, with implications for discriminating among them and thus, ultimately, for the correct modeling of the time-evolution of open quantum many-body systems.

To address the challenge of balancing limited quantum capabilities on the user side with communication efficiency in semi-quantum cryptography, this work introduces polarization and spatial-mode degrees of freedom (PSDF) single photons technology into the semi-quantum dialogue (SQD) framework and proposes a novel SQD protocol. This protocol employs parallel encoding across the dual degrees of freedom (DoFs) of single photons to achieve bidirectional secure communication, requiring only a single round of security verification. As the classical participant, Bob encodes his secret information via (Z_{P} otimes Z_{S}) basis measurements and re-preparation of states, returning quantum sequence to Alice. Alice decodes Bob's message based on her knowledge of the initial states and encodes her own secret information by applying specific unitary operations. In terms of security, the protocol effectively resists various active eavesdropping attacks. Furthermore, it incorporates one-way hash functions and error correction coding mechanisms to enhance robustness in noisy environments. The proposed scheme utilizes PSDF single photons product states as its quantum resource, whose preparation and measurement can be realized with existing mature experimental techniques, ensuring high practical feasibility. This work provides a new perspective for the practical development of semi-quantum communication systems.

State vector simulation is useful for designing and analyzing quantum algorithms. The challenge is that the size of the state vector increases exponentially with the number of quantum bits (qubits) and the entire state vector should be updated when simulating each quantum gate. Gate fusion, a circuit minimization technique, helps reduce simulation time by combining multiple quantum gates into one. However, the gate matrix will be large if the fused gate acts on too many qubits, which may increase the simulation costs. Previous work limits the size of fused gates based on the number of input qubits, but the impact of qubits’ types is neglected. This paper proposes a novel two-stage gate fusion strategy, namely QMin, based on the observation that control input qubits can reduce the simulation cost of a gate, which has not been discussed before. Specifically, QMin designs a pattern-controlled logic gate structure to fuse target gates apart from their control qubits. For the first target-oriented fusion stage, QMin defines beneficial mergeable gate types based on the required multiplication operations. The second tensor-oriented fusion stage merges gates under a constraint on the gate size to further reduce the number of gates. Experimental results on various circuits show that QMin can achieve more than 2.03 times speedup on average in total execution time compared with previous methods.

The celebrated Hong–Ou–Mandel effect illustrates the richness of two-photon interferometry. In this work, we demonstrate that this extends to the realm of time–frequency interferometry. Taking advantage of the mathematical analogy which can be drawn between the frequency and quadrature degrees of freedom of light when there is a single photon in each auxiliary mode, we consider the equivalent of the Hong–Ou–Mandel effect in the frequency domain. In this setting, the n-Fock state becomes equivalent to a single-photon state with a spectral wave function given by the (n^{th}) Hermite–Gauss function and destructive interference corresponds to vanishing probability of detecting single photons with an order one Hermite–Gauss spectral profile. This compelling analogy motivates us to propose an interferometric strategy that uses a frequency-engineered two-photon state to achieve enhanced phase precision that scales inversely with the number of modes. Finally, we generalize the Gaussian Boson sampling model to time–frequency degrees of freedom of single photons. Through all these applications, we emphasize that distinct types of quantum resources and degrees of freedom can yield identical statistical outcomes and information processing capabilities.

In this paper, thermofield dynamics (TFD) is applied to map a quantum optics nonlinear master equation into a Schrödinger-like equation for any arbitrary initial condition. This formalism provides a more efficient way for solving open quantum system problems. Then we use the Hartree–Fock approximation to solve the master equations of two separate noisy quantum systems analytically, which allows us to analyze the entanglement and quantum mutual information in each case using the eigenvalues of a covariance matrix, followed by two-mode and single-mode squeezed states.

The rapid development of neutral atom quantum hardware provides a unique opportunity to design hardware-centered algorithms for solving real-world problems aimed at establishing quantum utility. In this work, we study the performance of two such algorithms on solving MaxCut problem for various weighted graphs. The first method uses a state-of-the-art machine learning tool to optimize the pulse shape and embedding of the graph using an adiabatic Ansatz to find the ground state. We tested the performance of this method on finding maximum power section task of the IEEE 9-bus power system and obtaining MaxCut of randomly generated problems of size up to 12 on QuEra’s Aquila quantum processor. To the best of our knowledge, this work presents the first MaxCut results on Aquila quantum hardware. Our experiments run on Aquila demonstrate that even though the probability of obtaining the solution is reduced, one can still solve the MaxCut problem on cloud-accessed neutral atom analog quantum hardware, with an average 60% overlap for the graphs of 8 to 12 vertices studied. The second method uses local detuning, which is an emergent update on the Aquila hardware, to obtain a near exact realization of the standard QAOA Ansatz with similar performance. Finally, we study the fidelity throughout the time evolution realized in the adiabatic method as a benchmark for the IEEE 9-bus power grid graph state.

This paper presents a connection between the quantum walk and the absolute mathematics. The quantum walk is a quantum counterpart of the classical random walk. We especially deal with the Grover walk on the graph, which is a typical model of quantum walks. The time evolution of the Grover walk is obtained by a unitary matrix called the Grover matrix. We define a new type of the zeta function determined by the Grover matrix. Then, we consider to construct the absolute zeta function. In the previous paper [10], it is pointed out that there is a relationship between quantum walk and absolute zeta function. In the first half of this paper, we briefly describe the results of the previous research. In the latter part, we compute the absolute zeta function of the quantum walk by two different methods. One is calculated by the cyclotomic polynomial. The other is based on the series expansion. Its explicit derivation can be extended to a broader class of quantum walks on graphs.

SHA-256 exhibits strong resistance to collision attacks, a property attributed to its intricate design. Recently, Li et al. proposed a novel semi-free-start (SFS) collision attack targeting 39-step SHA-256, advancing prior methodologies. Despite these advancements, increasing the number of attackable rounds for SHA-256 remains challenging. This study demonstrates the conversion of a semi-free-start collision into a full collision attack through a specialized quantum technique. Using a quantum approach, our method targets 39-round SHA-256, leveraging frameworks that transform SFS collisions into two-block collisions, thereby establishing a new benchmark for collision attacks.

The quantum analysis method proposed in this paper achieves a circuit depth of (T_F le 3.4) and a circuit width of (S_F le 2.4). With a quantum computer of size S, this attack achieves a collision within time (t = 2^{124}/sqrt{S}). The attack is effective when the quantum computer size satisfies (2.4 le S < 2^8). Furthermore, this study investigates the conditions required to transform a semi-free-start collision into a two-block collision. It also examines the conversion of semi-free-start or free-start collision attacks into two-block collisions across various hash functions. The results indicate that the unique properties of quantum computing establish new benchmarks for collision attacks on hash functions.

This paper introduces a theoretical framework for asymmetric quad-directional controlled quantum teleportation (AQDCQT), offering a novel approach to simultaneous quantum state transmission among four users. In this protocol, any of the four users can concurrently transmit their entangled state to others, facilitated by a supervisory controller, utilizing a network of 29 qubits as the quantum channel. Quad-directional teleportation enables all four users to act simultaneously as both sender and receiver. Using the IBM Quantum platform, the quantum channel is implemented in practice. The protocol leverages Bell state measurement (BSM), GHZ state measurement (GHZ), and single-qubit measurement (SQM) for efficient quantum state teleportation. Regarding security, we address communication security measures against two potential attacks. The comparative analysis demonstrates the superior intrinsic efficiency of the proposed scheme when compared to previous approaches. Furthermore, we examine the impact of environmental noise on the channel, revealing that the protocol’s fidelity is influenced by the initial state's amplitude coefficient and the noise intensity.