Abstract Quantum computing represents a significant advancement in computational capabilities. Of particular concern is its impact on asymmetric cryptography through, notably, Shor’s algorithm and the more recently developed Regev’s algorithm for factoring composite numbers. We present our implementation of the latter with the aim of exposing experimental phenomena. Our analysis encompasses both quantum simulation results and classical component examples, with particular emphasis on comparative cases between Regev’s and Shor’s algorithms. Our experimental results reveal that Regev’s algorithm outperforms Shor’s algorithm for certain composite numbers in practice. However, we observed significant performance variations across different input values. Despite Regev’s algorithm’s theoretical asymptotic advantage in effectiveness, our implementation exhibited longer execution times than Shor’s algorithm for small-integer factorization in both quantum and classical components. These findings offer insights into the practical challenges and performance characteristics of implementing Regev’s algorithm in realistic quantum computing scenarios.
Abstract Quantum computing represents a significant advancement in computational capabilities. Of particular concern is its impact on asymmetric cryptography through, notably, Shor’s algorithm and the more recently developed Regev’s algorithm for factoring composite numbers. We present our implementation of the latter with the aim of exposing experimental phenomena. Our analysis encompasses both quantum simulation results and classical component examples, with particular emphasis on comparative cases between Regev’s and Shor’s algorithms. Our experimental results reveal that Regev’s algorithm outperforms Shor’s algorithm for certain composite numbers in practice. However, we observed significant performance variations across different input values. Despite Regev’s algorithm’s theoretical asymptotic advantage in effectiveness, our implementation exhibited longer execution times than Shor’s algorithm for small-integer factorization in both quantum and classical components. These findings offer insights into the practical challenges and performance characteristics of implementing Regev’s algorithm in realistic quantum computing scenarios.
Factoring large integers has long been a computationally difficult problem in classical computing, forming the foundation of widely used encryption methods like RSA. In 1994, Shor’s quantum algorithm introduced a revolutionary method for factoring integers exponentially faster than classical algorithms, laying the groundwork for quantum cryptography. Despite numerous attempts to enhance Shor’s algorithm over the last three decades, significant breakthroughs remained elusive until Regev’s discovery in 2023. Regev introduced a novel, multi-dimensional version of the quantum factoring algorithm, achieving a substantial improvement by reducing the required number of quantum gates to O(n^2 lo gn )(n^(3/2) logn ), compared to Shor’s originalO(n^2 lo gn )original O(n^2 logn ) gate complexity. Although Regev’s approach offers a significant speedup, it comes with increased qubit requirements and relies on an unproven number theory assumption. This paper presents an overview of Regev’s factoring algorithm, including a review of Shor’s work for context, followed by an examination of key recent developments and follow-up research. These include efforts to reduce the qubit count, improve error resilience, generalizegeneralise Regev’s algorithm to related problems, and validate the number theory assumption. This review serves as an accessible entry point for researchers interested in the rapidly evolving field of quantum computing and factoring algorithms.
Quantum algorithms for integer factorization represent one of the most prominent applications of quantum computation, with far-reaching implications for modern cryptography. While Shor's algorithm provides a polynomial-time solution in the ideal quantum model, its practical implementation is severely constrained by the limitations of current noisy intermediate-scale quantum (NISQ) hardware. These constraints have motivated the exploration of alternative factoring algorithms with different structural and resource trade-offs.
In this work, we present an experimental study of Regev's quantum factoring algorithm, implemented on real quantum hardware, and compare its behavior with that of Shor's algorithm under analogous conditions. Focusing on the case N = 15, we execute both algorithms on the QMIO quantum computer at the Centro de Supercomputacion de Galicia (CESGA) and contrast the results with one of IBM's open-access quantum computers and ideal simulations. This parallel execution enables a low-level comparison of the two algorithms, highlighting how their respective quantum implementations interact with hardware noise, limited circuit depth, and finite sampling.
Our analysis emphasizes the different ways in which Shor's and Regev's algorithms encode arithmetic structure into quantum states through Fourier sampling in one and higher dimensions, respectively, and how these differences manifest in experimental outcomes. Although neither algorithm demonstrates a practical advantage in the small N regime, the results provide insight into their relative robustness and failure modes on contemporary quantum devices. This study illustrates the value of experimental benchmarking of alternative quantum factoring algorithms as a means of understanding the practical implications of algorithmic design choices in the NISQ era.
The integer factorization problem (IFP) underpins the security of RSA, yet becomes efficiently solvable on a quantum computer through Shor's algorithm. Regev's recent high-dimensional variant reduces the circuit size through lattice-based post-processing, but introduces substantial space overhead and lacks practical implementations. Here, we propose a qubit reuse method by intermediate-uncomputation that significantly reduces the space complexity of Regev's algorithm, inspired by reversible computing. Our basic strategy lowers the cost from O(n3/2) to O(n5/4), and refined strategies achieve O(nlogn)which is a space lower bound within this model. Simulations demonstrate the resulting time-space trade-offs and resource scaling. Moreover, we construct and compile quantum circuits that factor N=35, verifying the effectiveness of our method through noisy simulations. A more simplified experimental circuit for Regev's algorithm is executed on a superconducting quantum computer, with lattice-based post-processing successfully retrieving the factors. These results advance the practical feasibility of Regev-style quantum factoring and provide guidance for future theoretical and experimental developments.
The field of quantum computing has witnessed remarkable advancements in recent years, particularly in its potential applications to solve computationally hard problems such as integer factorization. a comparative analysis of quantum computing algorithms for integer factorization, focusing on their theoretical foundations, computational complexity, and practical implications. We review prominent algorithms such as Shor's algorithm, which leverages quantum parallelism and period finding to efficiently factor large composite integers, and compare them with classical factorization algorithms like the General Number Field Sieve (GNFS). Through a comprehensive examination of algorithmic strategies, runtime complexities, and quantum circuit implementations, we assess the relative strengths and limitations of quantum computing approaches for integer factorization. Furthermore, we discuss potential challenges and future research directions in harnessing the power of quantum computing to address cryptographic security and algorithmic complexity in the era of post-quantum cryptography.
In this research, we investigate the relationships between classical and quantum computing, and the superior time complexity and memory allocation proposed theoretically for quantum algorithms. This is accomplished by building quantum circuits to represent algorithms and test in a quantum computer simulation. Classical circuit components have been continually reducing in size to the point where they are now being impacted by quantum properties, resulting in the need to investigate quantum computing. The inherent parallelism of quantum computing also allows us to solve problems for which classical computers are inept. The class of intractable problems in computing where the solution can only be found through exhaustive search is where we observe quantum computing supremacy. It is important to explore and advance our knowledge of quantum computing so we are prepared for when it becomes a reality, and so that in the future our understanding of encryption is deepened and new quantum-proof methods can be developed. Although Google and IBM have developed physical quantum computers, there is still a large deficit in knowledge of how they may be utilized. There is also a gap between proposed superior quantum solutions and problems demonstrably solved using quantum algorithms. Among the problems classically considered intractable is one extremely relevant to cybersecurity, known as Shor’s algorithm, that being an efficient algorithm for integer factorization, breaks down our well-established methods of cryptography. The aim of this research is to show the differences and advantages of quantum computing, and to specifically demonstrate how we can use Shor’s algorithm in a quantum system.
The advent of quantum computing poses a fundamental threat to classical cryptographic systems, particularly RSA encryption, which relies on the computational limit of prime factorization. This paper presents a comparative analysis of four integer factorization approaches-a selfcurated brute-force classical implementation, optimized Trial Division, Pollard's Rho algorithm, and Shor's algorithmevaluated across a dataset of increasing semiprime inputs representative of scaled-down RSA encryption keys. Through Python-based implementations and simulations, we empirically measure and plot runtime complexity for classical methods while modeling theoretical runtimes for Shor's algorithm, given hardware limitations. Our findings reveal the exponential scaling limitations of classical algorithms, and contrast them with the polynomial-time behavior of Shor's algorithm. Despite being simulated, Shor's consistently flatter runtime trendline demonstrated its theoretical superiority and the critical urgency of post-quantum cryptography. This study not only visualizes the performance divide between classical and quantum paradigms but also underscores the transformational potential of quantum computing in modern cryptanalysis.