According to Popular Mechanics, quantum computers face a surprising theoretical limitation beyond their well-known engineering challenges. While Google recently announced its quantum computer can run algorithms approximately 13,000 times faster than classical counterparts, new research from physicist Schuster and his team reveals that some fundamental questions may be impossible for quantum computers to answer. The study, uploaded to the preprint server arXiv, suggests that determining certain quantum phases could require computation times spanning billions of trillions of years, making them effectively unsolvable. This research builds on Schuster’s earlier work published in Science that focused on improving randomness in quantum computers, but now probes deeper questions about the computational limits of these machines and the nature of physical observation itself. This discovery challenges the assumption that quantum computing can eventually solve any computational problem.
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The Deeper Problem: Physical Observation Itself
What makes this research particularly significant is that it moves beyond the familiar engineering constraints of quantum computing—such as decoherence and error correction—to address fundamental theoretical boundaries. While we’ve known that current quantum computers struggle to surpass 1,000 qubits and would need approximately 20 million qubits to break classical cryptography, this new limitation strikes at the heart of what we can physically observe and compute. The researchers identified that properties like evolution time, phases of matter, and causal structure appear fundamentally difficult to learn through conventional quantum experiments. This suggests that the limitation isn’t just about processing power or algorithm efficiency, but about the very nature of physical reality and what can be known about it.
Cryptography’s Unexpected Protection
Ironically, while quantum computers threaten classical cryptography, these newly discovered limitations might actually provide unexpected protection for certain cryptographic systems. If some computational problems are fundamentally unsolvable regardless of computing power, this creates a natural barrier that even quantum supremacy cannot overcome. Schuster’s earlier work on generating randomness with fewer operations suggested easier paths to quantum cryptography, but these new findings indicate there may be inherent boundaries we cannot cross. This creates a fascinating dynamic where quantum computing both threatens existing security systems while simultaneously revealing natural limits that could protect others.
The Practical Consequences for Quantum Development
For companies like Google that are pushing quantum computing advancements, this research serves as both a warning and a guide. Rather than simply pursuing more qubits or faster processing, developers may need to focus on understanding which problems are actually solvable within quantum constraints. The “nightmare scenario” Schuster describes—where critical problems require impossibly long computation times—could redirect research priorities toward problems that are both important and fundamentally solvable. This might accelerate practical applications in materials science, drug discovery, and optimization problems while avoiding theoretical dead ends.
The Philosophical Dimension: Limits of Knowledge
Perhaps the most profound implication extends beyond computing to our understanding of physical reality itself. The research suggests that quantum superposition and entanglement, while powerful computational tools, may not overcome certain fundamental barriers to knowledge. This echoes historical debates in physics about the limits of observation and measurement, but now applies them to the most powerful computational systems we can envision. If even quantum computers cannot answer certain questions about quantum systems, we may be facing inherent limitations in what science can ultimately discover about the universe—a humbling realization in an age of rapid technological advancement.
Where Quantum Research Goes From Here
The immediate research direction should focus on characterizing which specific problems fall into this “unanswerable” category and why. As the preprint study indicates, not all quantum phase determination problems are impossible—the challenge is identifying the boundary between solvable and fundamentally unsolvable questions. This work will likely inspire new mathematical frameworks for classifying computational problems based on their quantum solvability. Meanwhile, practical quantum development should continue, but with greater awareness that some theoretical limits may be absolute rather than temporary engineering challenges.
