Vault12 Explains “Quantum Supremacy” Risks: Shor’s Algorithm Requires Millions of Fault-Tolerant Qubits

July 19, 2026

Vault12 USA

Overview

Vault12 clarifies that “quantum supremacy” refers to the point where quantum computers outperform classical counterparts on specific tasks. While quantum algorithms like Shor’s could theoretically break current internet security (RSA, elliptic curve cryptography), existing quantum computers are far from posing such a threat. Practical cryptanalysis would necessitate millions of stable, fault-tolerant qubits, a capability not yet achieved.

In Depth

Key Findings

Vault12 provides a clear explanation of the concept of “quantum supremacy” and its potential implications for current cryptographic systems. Quantum supremacy denotes the moment when a quantum computer can solve a specific computational task at speeds unattainable by even the fastest classical supercomputers, marking a significant milestone in the field.

Technical / Clinical Details

One of the most significant quantum algorithms, Shor’s algorithm, is capable of efficiently factoring large integers. This capability poses a theoretical threat to the bedrock of modern internet security, including public-key cryptographic schemes like RSA and Elliptic Curve Cryptography. Since these encryption methods rely on the computational difficulty of factoring large numbers, the practical realization of Shor’s algorithm could enable the decryption of much of our currently encrypted communications and data. However, it is crucial to understand that executing Shor’s algorithm and breaking real-world cryptographic systems demands not just a large number of qubits, but millions of ‘fault-tolerant’ qubits that exhibit extremely low error rates and can maintain quantum information stability over extended periods. Current quantum computers are far from achieving this level of performance and reliability.

Background & Context

The term “quantum supremacy” itself has been debated, with some preferring more cautious terminology like “quantum advantage” to avoid misinterpretations. Google’s 2019 claim of quantum supremacy with its “Sycamore” processor, which reportedly outperformed classical supercomputers on a specific random circuit sampling problem, subsequently faced scrutiny, with later demonstrations of classical algorithmic approaches that could replicate or challenge the results. The quantum computing industry largely operates in the Noisy Intermediate-Scale Quantum (NISQ) era, characterized by mid-sized quantum computers with inherent error rates, implying a significant journey remains toward building large-scale, truly fault-tolerant quantum machines.

Strategic Significance & Outlook

While the concept of quantum supremacy remains a crucial benchmark for illustrating the potential of quantum computing, it is important to recognize that it does not immediately threaten current cryptographic systems. Research and development efforts are intensely focused on building stable logical qubits and advancing quantum error correction techniques. In the future, should quantum computers with millions of fault-tolerant qubits become a reality, the cybersecurity landscape would indeed be revolutionized. Consequently, governments and corporations worldwide are accelerating their transition to Post-Quantum Cryptography (PQC) and developing technologies like Quantum Key Distribution (QKD). It is imperative to cautiously monitor the progress of quantum technology while actively implementing countermeasures to preempt future threats.

Source: https://vault12.com/blog/quantum-supremacy/what-is-quantum-supremacy-and-why-it-sounds-scary

Get our weekly technology intelligence — free

Receive an infographic that lets you judge at a glance whether each field’s analysis report is worth reading.

Subscribe Free — Weekly Tech Intelligence

By subscribing, you’ll receive Troy-Technical’s weekly technology intelligence newsletter.