A massive gap exists between current quantum computing (QC) prototypes, and the size and scale required for many proposed QC algorithms. Current QC implementations are prone to noise and variability which affect their reliability, and yet with less than 80 quantum bits (qubits) total, they are too resource-constrained to implement error correction. The term Noisy Intermediate-Scale Quantum (NISQ) refers to these current and near-term systems of 1000 qubits or less. Given NISQ's severe resource constraints, low reliability, and high variability in physical characteristics such as coherence time or error rates, it is of pressing importance to map computations onto them in ways that use resources efficiently and maximize the likelihood of successful runs. This paper proposes and evaluates backend compiler approaches to map and optimize high-level QC programs to execute with high reliability on NISQ systems with diverse hardware characteristics. Our techniques all start from an LLVM intermediate representation of the quantum program (such as would be generated from high-level QC languages like Scaffold) and generate QC executables runnable on the IBM Q public QC machine. We then use this framework to implement and evaluate several optimal and heuristic mapping methods. These methods vary in how they account for the availability of dynamic machine calibration data, the relative importance of various noise parameters, the different possible routing strategies, and the relative importance of compile-time scalability versus runtime success. Using real-system measurements, we show that fine grained spatial and temporal variations in hardware parameters can be exploited to obtain an average 2.9x (and up to 18x) improvement in program success rate over the industry standard IBM Qiskit compiler. Despite small qubit counts, NISQ systems will soon be large enough to demonstrate "quantum supremacy", i.e., an advantage over classical computing. Tools like ours provide significant improvements in program reliability and execution time, and offer high leverage in accelerating progress towards quantum supremacy.

https://dl.acm.org/doi/pdf/10.1145/3297858.3304075

Noise-Adaptive Compiler Mappings for Noisy Intermediate-Scale Quantum Computers

Quantum computing is an emerging paradigm with the potential to offer significant computational advantage over conventional classical computing by exploiting quantum-mechanical principles such as entanglement and superposition. It is anticipated that this computational advantage of quantum computing will help to solve many complex and computationally intractable problems in several areas such as drug design, data science, clean energy, finance, industrial chemical development, secure communications, and quantum chemistry. In recent years, tremendous progress in both quantum hardware development and quantum software/algorithm have brought quantum computing much closer to reality. Indeed, the demonstration of quantum supremacy marks a significant milestone in the Noisy Intermediate Scale Quantum (NISQ) era - the next logical step being the quantum advantage whereby quantum computers solve a real-world problem much more efficiently than classical computing. As the quantum devices are expected to steadily scale up in the next few years, quantum decoherence and qubit interconnectivity are two of the major challenges to achieve quantum advantage in the NISQ era. Quantum computing is a highly topical and fast-moving field of research with significant ongoing progress in all facets. This article presents a comprehensive review of quantum computing literature, and taxonomy of quantum computing. Further, the proposed taxonomy is used to map various related studies to identify the research gaps. A detailed overview of quantum software tools and technologies, post-quantum cryptography and quantum computer hardware development to document the current state-of-the-art in the respective areas. We finish the article by highlighting various open challenges and promising future directions for research.

Quantum Computing: A Taxonomy, Systematic Review and Future Directions

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Μετακβαντικοί κρυπτογραφικοί αλγόριθμοι (Post-Quantum Cryptography)

Quantum computing: A taxonomy, systematic review and future directions

This paper describes the work carried out by the Inter-American Development Bank, the IDB Lab, LACChain, Cambridge Quantum Computing (CQC), and Tecnologico de Monterrey to identify and eliminate quantum threats in blockchain networks. 
The advent of quantum computing threatens internet protocols and blockchain networks because they utilize non-quantum resistant cryptographic algorithms. When quantum computers become robust enough to run Shor's algorithm on a large scale, the most used asymmetric algorithms, utilized for digital signatures and message encryption, such as RSA, (EC)DSA, and (EC)DH, will be no longer secure. Quantum computers will be able to break them within a short period of time. Similarly, Grover's algorithm concedes a quadratic advantage for mining blocks in certain consensus protocols such as proof of work. 
Today, there are hundreds of billions of dollars denominated in cryptocurrencies that rely on blockchain ledgers as well as the thousands of blockchain-based applications storing value in blockchain networks. Cryptocurrencies and blockchain-based applications require solutions that guarantee quantum resistance in order to preserve the integrity of data and assets in their public and immutable ledgers. We have designed and developed a layer-two solution to secure the exchange of information between blockchain nodes over the internet and introduced a second signature in transactions using post-quantum keys. Our versatile solution can be applied to any blockchain network. In our implementation, quantum entropy was provided via the IronBridge Platform from CQC and we used LACChain Besu as the blockchain network.

Quantum-Resistance in Blockchain Networks

Blockchain is one of the most revolutionary and innovative technologies in recent years. The traditional asymmetric encryption algorithms guarantee the security of data on blockchain. However, with the rapid development of quantum computing technologies, as long as large-scale quantum computers appear, these kind of encryption systems can be deciphered by shor algorithm in polynomial time. Therefore, blockchain technologies are going to face potential security threats. To solve this problem, the best solution at present is to replace the asymmetric encryption algorithms in the blockchain with post-quantum cryptosystems. In this paper, we apply the Rainbow algorithm with high signature efficiency to the existing Ethereum platform, and test the feasibility of the scheme by building a private chain. In addition, we compare the signature efficiency of Rainbow algorithm with ECDSA, which is expected to provide direction and inspiration for future research on blockchain resistance to quantum computing.

Application and Implementation of Multivariate Public Key Cryptosystem in Blockchain (Short Paper)

Recently, the development of quantum chips has made great progress – the number of qubits is increasing and the fidelity is getting higher. However, qubits of these chips are not always fully connected, which sets additional barriers for implementing quantum algorithms and programming quantum programs. In this paper, we introduce a general circuit optimizing scheme, which can efficiently adjust and optimize quantum circuits according to arbitrary given qubits’ layout by adding additional quantum gates, exchanging qubits and merging single-qubit gates. Compared with the optimizing algorithm of IBM’s QISKit, the quantum gates consumed by our scheme is 74.7%, and the execution time is only 12.9% on average.

An Efficient Quantum Circuits Optimizing Scheme Compared with QISKit (Short Paper)

Nowadays, collaborative filtering methods have been widely applied to E-commerce platforms. However, due to its openness, a large number of spammers attack those systems to manipulate the recommendation results to earn huge profits. The shilling attack has become a major threat to collaborative filtering systems. Therefore, effectively detecting shilling attacks is a crucial task. Most existing detection methods based on statistical-based features or unsupervised methods rely on a priori knowledge about attack size. Besides, the majority of work focuses on rating attack and ignore the relation attack. In this paper, motivated by the success of heterogeneous information network and oriented towards the hybrid attack, we propose an approach DMD to detect shilling attack based on meta-path and matrix factorization. At first, we concatenate the user-item bipartite network and user-user relation network as a whole. Next, we design several meta-paths to guide the random walk to product node sequences and utilize the skip-gram model to generate user embeddings. Meanwhile, users’ latent factors are decomposed by matrix factorization. Finally, we incorporate these embeddings and factors to joint train the detector. Extensive experimental analysis on two public datasets demonstrate the superiority of the proposed method and show the effectiveness of different attack strategies and various attack sizes.

Hong Xiang

Papers

Application and Implementation of Multivariate Public Key Cryptosystem in Blockchain (Short Paper)

An Efficient Quantum Circuits Optimizing Scheme Compared with QISKit (Short Paper)

Meta-Path and Matrix Factorization Based Shilling Detection for Collaborate Filtering