University of Kwazulu-Natal

Quantum Computing Achieves Historic Unconditional Speedup

Bonisiwe Shabane
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quantum computing achieves historic unconditional speedup

Quantum computing has taken a major step forward with a breakthrough demonstrating an unconditional exponential speedup—a long-awaited milestone in the field. Led by Daniel Lidar, a professor of engineering at the University of Southern California (USC) and a leading expert in quantum error correction, the research was carried out in collaboration with teams from USC... Their findings were published in Physical Review X. Quantum computers have promised transformative capabilities: solving complex equations, designing next-generation medicines, breaking encryption, and discovering new materials. However, one persistent barrier has slowed progress—noise. These small but constant errors disrupt quantum operations, often rendering results less reliable than those from traditional classical computers.

Using IBM’s 127-qubit Eagle quantum processors—remotely accessed via the cloud—Lidar’s team successfully demonstrated an exponential speedup in solving a specific computational task. Unlike previous examples of modest or conditional quantum speedups, this result is exponential and unconditional. That means the performance gap between quantum and classical systems continues to widen as the problem size grows, and the advantage does not rely on any unproven assumptions or theoretical loopholes. The experiment focused on a problem known as Simon’s problem, a theoretical benchmark in quantum computing. This task requires uncovering a hidden repeating pattern within a mathematical function—a type of problem that quantum systems can solve exponentially faster than classical ones. The research team adapted this problem and fine-tuned an algorithm to make it compatible with existing quantum hardware.

Achieving this breakthrough required several innovations to suppress noise and enhance performance: Quantum computers have the potential to speed up computation, help design new medicines, break codes, and discover exotic new materials -- but that's only when they are truly functional. One key thing that gets in the way: noise or the errors that are produced during computations on a quantum machine -- which in fact makes them less powerful than classical computers - until... Daniel Lidar, holder of the Viterbi Professorship in Engineering and Professor of Electrical & Computing Engineering at the USC Viterbi School of Engineering, has been iterating on quantum error correction, and in a new... The paper, "Demonstration of Algorithmic Quantum Speedup for an Abelian Hidden Subgroup Problem," was published in APS flagship journal Physical Review X. "There have previously been demonstrations of more modest types of speedups like a polynomial speedup, says Lidar, who is also the cofounder of Quantum Elements, Inc.

"But an exponential speedup is the most dramatic type of speed up that we expect to see from quantum computers." The key milestone for quantum computing, Lidar says, has always been to demonstrate that we can execute entire algorithms with a scaling speedup relative to ordinary "classical" computers. Researchers from USC and Johns Hopkins used two IBM Eagle quantum processors to pull off an unconditional, exponential speedup on a classic “guess-the-pattern” puzzle, proving—without assumptions—that quantum machines can now outpace the best classical... By squeezing extra performance from hardware with shorter circuits, transpilation, dynamical decoupling, and error-mitigation, the team finally crossed a milestone long called the “holy grail” of quantum computing. Quantum computers have long promised to revolutionize technology, with the ability to speed up complex calculations, design new medicines, break modern encryption, and uncover exotic new materials. But there’s been a major obstacle: noise.

That’s the term for all the tiny errors that build up during quantum computations, often making these futuristic machines less effective than even today’s classical computers. A breakthrough led by Daniel Lidar, a professor of engineering at USC and an expert in quantum error correction, has pushed quantum computing past a key milestone. Working with researchers from USC and Johns Hopkins, Lidar’s team demonstrated a powerful exponential speedup using two of IBM’s 127-qubit Eagle quantum processors — all operated remotely through the cloud. Their results were published in the prestigious journal Physical Review X. “There have previously been demonstrations of more modest types of speedups like a polynomial speedup, says Lidar, who is also the cofounder of Quantum Elements, Inc. “But an exponential speedup is the most dramatic type of speed up that we expect to see from quantum computers.”

Conducted on IBM quantum processors, study demonstrates “a promise of quantum computing previously articulated only on paper.” Interior shot of a quantum computer with an IBM Eagle processor/Photo credit: IBM Quantum computers have the potential to speed up computation, help design new medicines, break codes, and discover exotic new materials—but that’s only when they are truly functional. One key thing that gets in the way: noise or the errors that are produced during computations on a quantum machine–which in fact makes them less powerful than classical computers – until recently. Daniel Lidar, holder of the Viterbi Professorship in Engineering and Professor of Electrical & Computing Engineering at the USC Viterbi School of Engineering, has been iterating on quantum error correction, and in a new... The paper, “Demonstration of Algorithmic Quantum Speedup for an Abelian Hidden Subgroup Problem,” was published in APS flagship journal Physical Review X.

In a landmark achievement for quantum computing, researchers from the University of Southern California and Johns Hopkins University have demonstrated what many consider the holy grail of the field: an unconditional exponential quantum speedup. The team, led by Professor Daniel Lidar, holder of the Viterbi Professorship in Engineering at USC, utilized two of IBM's 127-qubit Eagle quantum processors to solve a variation of Simon's problem—a mathematical challenge considered... Their results were published in Physical Review X on June 5, 2025. "The performance separation cannot be reversed because the exponential speedup we've demonstrated is, for the first time, unconditional," explains Lidar. What makes this speedup "unconditional" is that it doesn't rely on any unproven assumptions about classical algorithms, unlike previous quantum advantage claims. To achieve this breakthrough, the researchers implemented sophisticated error mitigation techniques, including dynamical decoupling and measurement error mitigation.

These methods helped maintain quantum coherence and improve result accuracy despite the inherent noise in current quantum hardware. The exponential speedup means the performance gap between quantum and classical approaches roughly doubles with each additional variable in the problem. As quantum processors continue to improve in quality and scale, this advantage will only grow more pronounced. Interior shot of a quantum computer with an IBM Eagle processor. Credit: IBM For decades, quantum computing has promised to revolutionize the way we solve problems, design drugs, discover new materials, and crack codes.

But until now, that promise lived mostly on paper—a thrilling theoretical dream constantly delayed by an inescapable nuisance: noise. These microscopic whispers of error, generated during the fragile dance of qubits inside a quantum processor, have long kept quantum computers trailing behind their classical cousins. Now, in a remarkable leap forward, a team of researchers led by Daniel Lidar at the University of Southern California has changed the game. They’ve demonstrated, for the first time, an unconditional exponential speedup using real quantum hardware—an achievement once confined to mathematical proofs and theoretical labs. Their study, published in the prestigious journal Physical Review X, marks a pivotal moment in the race toward usable quantum advantage. “This is not a simulation.

This is not a prediction. This is not a speedup that depends on any ‘if’ or ‘maybe’ about classical algorithms,” said Lidar, a professor of engineering, chemistry, and physics at USC and co-founder of Quantum Elements, Inc. “This is a demonstration of quantum performance that scales exponentially better than anything classical computing can offer for this task.” An interior view of the cryostat that cools the IBM Eagle, a utility-scale quantum processor containing 127 qubits. Credit: IBM Research For years, quantum computing has been a promise just out of reach—powerful, mysterious, and largely theoretical.

But now, scientists have crossed a pivotal threshold. A team from the University of Southern California and Johns Hopkins University has successfully demonstrated a quantum computer’s superiority over classical machines—without relying on assumptions or ideal conditions. Unlike previous demonstrations that hinged on hypothetical limits of classical computing, this new achievement offers unambiguous evidence. Researchers used real quantum processors—not simulations—to prove an exponential speedup over classical methods in solving a specific mathematical challenge. The team tackled a variation of Simon’s Problem, a foundational puzzle in quantum computing. While this problem is known to be tough for traditional systems, quantum algorithms can solve it exponentially faster.

The twist? They did it on actual hardware: IBM’s advanced 127-qubit Eagle processors. Simon’s Problem may sound like abstract math, but it’s actually a gateway to unlocking real-world algorithms like Shor’s (which could eventually break modern encryption). The fact that this experiment didn’t rely on theoretical assumptions means the quantum edge is not just real—it’s demonstrable and repeatable.

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