IET Quantum Communication最新文献

This study addresses the optimisation of on-demand routing protocols for quantum wireless Ad Hoc network. The study improves the route discovery protocol by proposing a ‘reverse synchronisation method’, which means after the route request is completed, the quantum channel establishment process can be carried out simultaneously with the route reply process. This method is better than the general method which builds quantum channels after the forward path establishment, reduces the time and the number of messages for quantum channel establishment, thus improving the efficiency. Accordingly, this study elaborates the specific methods, procedures and related upgrading message formats involved in quantum route discovery, quantum channel establishment and qubit information transmission of on-demand routing protocol for quantum wireless Ad Hoc network.

Deep neural networks were previously used in the arena of image retrieval. Siamese network architecture is also used for image similarity comparison. Recently, the application of quantum computing in different fields has gained research interest. Researchers are keen to explore the prospect of quantum circuit implementation in terms of supervised learning, resource utilization, and energy-efficient reversible computing. In this study, the authors propose an application of quantum circuit in Siamese architecture and explored its efficiency in the field of exudate-affected retinal image patch retrieval. Quantum computing applied within Siamese network architecture may be effective for image patch characteristic comparison and retrieval work. Although there is a restriction of managing high-dimensional inner product space, the circuit with a limited number of qubits represents exudate-affected retinal image patches and retrieves similar patches from the patch database. Parameterized quantum circuit (PQC) is implemented using a quantum machine learning library on Google Cirq framework. PQC model is composed of classical pre/post-processing and parameterized quantum circuit. System efficiency is evaluated with the most widely used retrieval evaluation metrics: mean average precision (MAP) and mean reciprocal rank (MRR). The system achieved an encouraging and promising result of 98.1336% MAP and 100% MRR. Image pixels are implicitly converted to rectangular grid qubits in this experiment. The experimentation was further extended to IBM Qiskit framework also. In Qiskit, individual pixels are explicitly encoded using novel enhanced quantum representation (NEQR) image encoding algorithm. The probability distributions of both query and database patches are compared through Jeffreys distance to retrieve similar patches.

A detailed investigation of the multiparty entanglement present in the 4 − qubit quantum hypergraph states is presented, following a measurement-based geometrical approach. Considering a classification of the 4 − party quantum system represented by a mathematical hypergraph based on the connections between its vertices, the genuine 4 − party entanglement present in each bi-partition of the states have been measured. A strong correlation between the connectivity of the vertices of the hypergraphs and the genuine 4 − party entanglement has been found. The equivalence of the genuine 4 − party entanglement present in each bi-partition is shown considering similar connectivity of the vertices. This explicates the cyclic permutation symmetry of the multiparty entanglement present in the 4 − qubit hypergraph states. Physically, one may expect the quantum systems with superposition of many states to behave in this symmetric manner while mapped into a network-type picture, which the authors have quantified, as well as classified in this work.

Ant colony optimisation (ACO) is a commonly used meta-heuristic to solve complex combinatorial optimisation problems like the travelling salesman problem (TSP), vehicle routing problem (VRP) etc. However, classical ACO algorithms provide better optimal solutions but do not reduce computation time overhead to a significant extent. Algorithmic speed-up can be achieved by using parallelism offered by quantum computing. Existing quantum algorithms to solve ACO are either quantum-inspired classical algorithms or hybrid quantum-classical algorithms. Since all these algorithms need the intervention of classical computing, leveraging the true potential of quantum computing on real quantum hardware remains a challenge. This study's main contribution is to propose a fully quantum algorithm to solve ACO, enhancing the quantum information processing toolbox in the fault-tolerant quantum computing (FTQC) era. We have solved the single source single destination (SSSD) shortest-path problem using our proposed adaptive quantum circuit for representing the dynamic pheromone-updating strategy in real IBMQ devices. Our quantum ACO technique can be further used as a quantum ORACLE to solve complex optimisation problems in a fully quantum setup with significant speed up upon the availability of more qubits.

A composable design scheme is presented for the development of hybrid quantum/classical algorithms and workflows for applications of quantum simulation. The proposed object-oriented approach is based on constructing an expressive set of common data structures and methods that enables programming of a broad variety of complex hybrid quantum simulation applications. The abstract core of the scheme is distilled from the analysis of the current quantum simulation algorithms. Subsequently, it allows synthesis of new hybrid algorithms and workflows via the extension, specialisation, and dynamic customisation of the abstract core classes defined by the proposed design. The design scheme is implemented using the hardware-agnostic programming language QCOR into the QuaSiMo library. To validate the implementation, the authors test and show its utility on commercial quantum processors from IBM and Rigetti, running some prototypical quantum simulations.

Quantum key distribution (QKD) systems enable secure key generation between two parties. Such systems require an authenticated classical channel for QKD protocols to work. Usually, the initial authentication key for this channel is pre-shared. In this work, methods that are used to renew the pre-shared keys ensuring a high level of security and performance for the subsequent quantum key generation are discussed. The model of QKD systems in terms of the lifecycle of the keys is formalised and a full set of parameters that can be used for key renewal functions is described. A detailed adversary model allows us to compare key renewal schemes by the probabilities of successful attacks and their consequences. As a result, it is shown that a hybrid key renewal scheme, which uses both the auxiliary pre-shared key and a part of the quantum sequence, has the higher security properties among considered schemes and is recommended to be used in QKD systems.

True random number generators (TRNGs) allow the generation of true random bit sequences, guaranteeing the unpredictability and perfect balancing of the generated values. TRNGs can be realised from the sampling of quantum phenomena, for instance, the detection of single photons. Here, a recently proposed technique, which implements a quantum random number generator (QRNG) out of a device that was realised for a different scope, is further analysed and certified [1]. The combination of a CMOS single-photon avalanche diode (SPAD) array, a high-resolution time-to-digital converter (TDC) implemented on a field programmable gate array (FPGA), the exploitation of a single-photon temporal degree of freedom, and an unbiased procedure provided by H. Zhou and J. Bruck [2, 3] allows the generation of true random bits with a high bitrate in a compact and easy-to-calibrate device. Indeed, the use of the ‘Zhou–Bruck’ method allows the removal of any correlation from the binary representation of decimal data. This perfectly fits with the usage of a device with non-idealities like SPAD's afterpulses, pixel cross-correlation, and time-to-digital converter non-uniform conversion. In this work, an in-depth analysis and certification of the technique presented in [1] is provided by processing the data with the NIST suite tests in order to prove the effectiveness and validity of this approach.

Satellite-based, long-distance free-space quantum key distribution has the potential to realise global quantum secure communication networks. Detecting faint quantum optical pulses sent from space requires highly accurate and robust classical timing systems to pick out signals from the noise and allow for reconciliation of sent and received key bits. For such high-loss applications, a fault-tolerant synchronisation signal coding and decoding scheme based on de Bruijn sequences is proposed. A representative synchronisation timing system was tested in laboratory conditions and it demonstrated high fault tolerance for the error-correction algorithm even under high loss. The performance limitations of this solution are also discussed, and the maximum error tolerance of the scheme and the estimated computational overhead are analysed, allowing for the possibility of implementation on a real-time system-on-chip. This solution not only can be used for synchronisation of high-loss channels such as channels between satellites and ground stations but can also be extended to applications with low loss, high bit error rate, but require reliable synchronisation such as quantum and non-quantum communications over terrestrial free space or fibre optic channels.