Quantum Information Processing最新文献

This paper is twofold. In the first part, we introduce an infinite family of new solutions to the parameter-dependent Yang–Baxter equation in any dimension (dge 2). Through a well-established conventional approach, we construct these solutions, which are of the form (I+uR), by means of recently discovered new solutions R to the constant Yang–Baxter equation. We demonstrate that these solutions are entangling under a relatively mild condition. However, simple calculations confirm that they fail to be unitary. In the second part, drawing inspiration from the conventional approach, we ponder the following question. Is it possible to construct a new solution of the form (I+uQ) to the parameter-dependent Yang–Baxter equation upon a matrix Q that is not necessarily a solution to the Yang–Baxter equation? To find an answer to this question, we deviate from the conventional approach by directly defining Q(u) (Q for short), which represents a u-deformation of the recently discovered solution R to the constant Yang–Baxter equation. Although Q is not a solution to the Yang–Baxter equation, nevertheless, we prove that (I+uQ) constitutes another infinite family of new solutions to the parameter-dependent Yang–Baxter equation. This family contains a large subfamily of both unitary and entangling solutions. We believe that this approach, when applied in a more general context, has the potential to open new avenues for discovering additional new solutions to the parameter-dependent Yang–Baxter equation in any dimension. Indeed, this is the common pursuit shared by many researches in Mathematics and Physics.

Blind signatures play a crucial and extensive role in security protocols where the anonymity of participants is paramount. Here, we propose an efficient quantum blind signature (QBS) protocol combining quantum key distribution (QKD), onetime pad (OTP), and onetime cryptographic cyclic redundancy codes hashing (OT-CRC-H), achieving information-theoretically secure blind signatures for arbitrary length documents. We simulated the performance of our protocol separately in a quantum network constructed using discrete-variable (DV) and continuous-variable (CV) QKD. Simulations demonstrate that in gigahertz systems within a 200-km range for signing one-megabit documents, QBS with DV QKD achieves a signature rate exceeding 588 times per second (tps), while QBS with CV QKD reaches 183 tps. In the sending-or-not-sending twin-field quantum network, QBS achieves a signature efficiency three times higher than a multi-bit quantum digital signature (QDS) and (10^{9}) times faster than a single-bit QDS. Notably, the protocol maintains compatibility with various QKD implementations and represents the first protocol for quantum blind signatures based on QKD. Our work establishes a new solution for practical quantum-enhanced signature implementations in quantum networks.

It has been shown that the entanglement between the system and ancillary states is not a strict requirement for performing ancilla-assisted process tomography (AAPT). Instead, from a theoretical point of view, it only requires that the system-ancilla state be faithful, which, in the qubit case, is the invertibility of a certain matrix representing the state. Our paper takes on the operational definition of faithfulness, i.e., a state is faithful if one can extract complete information about the quantum process, and we restrict the process to single-qubit operations on a two-qubit system-ancilla state. We present a theoretical analysis that connects the invertibility problem to the concept of Sinisterness, which quantifies the correlation between two qubits and can be generalized to bipartite systems formed by qubits for a certain class of states. Using Sinisterness, we derive a way of constructing two-qubit states that are guaranteed to be faithful and estimate the bound on the average error of the process featured by the condition number. Our analysis agrees that the maximally entangled states provided the smallest error amplification. Nevertheless, it maps out a numerical region where the advantage of the entanglement starts.

Most existing protocols for blind quantum computation (BQC) focus on single-client scenarios, leaving multi-client situations largely unexamined. However, involving more participants increases security risks. In this paper, we present a multi-party verifiable blind quantum computation protocol that incorporates mutual authentication to address these threats. The protocol is divided into three phases. First, we enhance the key-generation method proposed by Yang et al. by substituting Bell-state measurements with single-qubit measurements. This change results in a more deterministic and experimentally simpler approach to distributing authentication keys. Second, clients and servers perform mutual identity verification based on these keys, effectively countering both insider and outsider attacks. Third, after successful authentication, clients delegate the actual computation to the servers while keeping their data, algorithms, and outputs hidden. Each client is only required to locally apply the single-qubit phase gate S. Additionally, trap-based checks enable every client to verify the correctness of the final result. Compared to existing schemes, our protocol simultaneously minimizes the quantum capability requirements for clients—allowing them to perform only the S operation—and reduces implementation costs by eliminating the need for Bell measurements.

Subsystem codes (Q=Aotimes B) are a generalization of noiseless subsystems, decoherence-free subspaces, and quantum error-correcting codes. In this paper, we provide an effective method for constructing subsystem codes via matrix-product codes. In addition, the lengths, dimensions of subsystem A and the co-subsystem B, and minimum distances of our subsystem codes (Q=Aotimes B) are easily calculated.

Existing quantum key distribution (QKD) cannot transmit data directly, while quantum secure direct communication (QSDC) is limited in directly ensuring data security due to its pre-audit mechanism separated from the data payload. This paper proposes a new protocol, quantum trust data distribution (QTDD), to overcome these limitations. The core of QTDD lies in reinterpreting the stabilizer formalism from the quantum error correction field not for error recovery, but as a robust security verification mechanism embedded within the data payload itself. This approach enables not only security verification to detect eavesdroppers but also preserves multi-qubit states after continuous reception by leveraging the non-destructive nature of stabilizer measurements. This direct, continuous, and always-on verification capability forms the foundation for building trust in distributed quantum data. Consequently, QTDD moves beyond the one-time generate-and-consume model of QKD and QSDC, enabling a continuous and verifiable quantum resource model.

This paper proposes a novel probabilistic version of the Game of Life and a quantum model for it. Based on the study and formalisation of the traditional deterministic case, the quantum paradigm is presented as a good candidate for modelling probabilistic behaviour, providing a convenient description of the problem and efficient calculation of the necessary probabilities in an intrinsic way. To illustrate the advantages of quantum computing for this calculation, two implementations are presented: a classical version developed in Rust and a quantum version built using IBM’s Qiskit quantum circuit software. The particularities of this model are presented, its applications are discussed, and optimisations are suggested for the general case, where different neighbourhood sizes and geometries or an increased number of dimensions can be considered. For the particular case of the traditional Game of Life and for all these extended cases, competitive complexity is demonstrated through the quantum paradigm, with respect to the exhaustive classical calculation of probabilities or approximate methods. This allows cases with many dimensions or complex conditions to be executed efficiently.

This article reports on the development of quantum communication technologies at IIT Madras, India, with a focus on the realisation of the Metro Area Quantum Access Network (MAQAN), India’s first multi-node quantum key distribution (QKD) network field-tested across Chennai. The MAQAN network exclusively integrates the Coherent One-Way (COW) and Differential Phase Shift (DPS) QKD protocols, demonstrating their robustness and compatibility with urban fibre infrastructure for secure key generation. In addition to the metro-scale network deployment, we present tabletop experimental results for phase-encoded BB84 implementations over fibre links of varying lengths and introduce new advances in Differential Phase Shift Measurement-Device-Independent QKD (DPS-MDI-QKD) with proof-of-principle demonstrations. The article analyses key challenges and proposed solutions for phase stabilisation, synchronisation, and secure key rate optimisation in real-world quantum communication environments. These results provide a solid foundation for the future integration of advanced QKD protocols into MAQAN and for the planned extension of interconnected quantum networks across multiple Indian cities as part of the QuILA (Quantum Internet with Local Access) initiative, aimed at establishing a robust quantum communication backbone for India.

We develop translation techniques from an NFA to a quantum circuit to validate the correctness of a system modeled by an NFA—a problem that is computationally intractable on conventional computers. Specifically, we solve a model validation problem in three steps. First, we translate a given NFA into an equivalent Quantum Finite-state Automaton (QFA) such that it accepts or rejects all bounded strings in their superposition and synthesize a quantum circuit for the QFA. Second, we extend the QFA circuit to simulate the time evolution of quantum states under a Hamiltonian that represents the acceptance of strings. Finally, using QAOA, we amplify the amplitudes of accepted strings so that they are measured more frequently. In addition, we apply Grover’s search algorithm for the accepted strings and compare the results with those of QAOA. Our work represents the first proposal to apply quantum computing to the problem of verifying conventional systems; our approach would facilitate software verification, program analysis, protocol design, and verification of circuits, among other applications.

We discuss the application of the Jordanian quantum algebra (mathcal {U}_h (mathfrak {sl}(2, mathbb {R}))), a Hopf algebra deformation of the Lie algebra (mathfrak {sl}(2, mathbb {R})), in order to generate sets of N qubit quantum states. We construct the associated h-deformed Dicke states using the Clebsch–Gordan coefficients for (mathcal {U}_h (mathfrak {sl}(2, mathbb {R}))), showing that the former exhibit completely different features than the q-Dicke states obtained from the standard quantum deformation ({mathcal {U}}_q (mathfrak {sl}(2, mathbb {R}))). Moreover, the density matrices of these h-deformed Dicke states are compared to the experimental realizations of those of Dicke states, and several similarities are observed, indicating that the h-deformation could be used to describe noise and decoherence effects in experimental settings, as well as to control the degree of entanglement of the state in quantum computing protocols. In particular, h-Dicke states for (N=2,3,4) are presented, a method to construct the h-deformed analogs of W-states for arbitrary N is given, and some algebraic considerations for the explicit derivation of generic h-Dicke states are provided.