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Qubits Are at the Heart of Quantum Computing. They're Also Its Greatest Weakness

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Artist's conception of a qubit.

The researchers said Google's claims are challenging to analyze because Google chose a quantum computing task that was difficult to compare to any known algorithm in classical computation.

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Entanglement is the other major quantum phenomenon enabling qubits to pass information to one another in a quantum computer. This is the idea that particles can be linked in such a way that they can't be described independently. Changing one particle by performing a measurement instantly changes its entangled partner, no matter how far apart the two particles are, even if they're on opposite ends of the universe. This troubled Albert Einstein so much that he described entanglement as "spooky action at a distance."

The application of these quantum elements means that while adding bits to a traditional computer scales its computing power linearly, adding qubits to a quantum computer scales it exponentially. Mathematically, that means if a quantum computer has n qubits, these can exist in a superposition of 2n states.

The entanglement of qubits, and storing information in a superposition, makes quantum computers more powerful than classical computers, and results in a system that can solve problems exponentially faster. But, there's a catch. A big one. Quantum states like entanglement and superposition are incredibly delicate, and easily destroyed. And that's a major setback for the reliability of quantum computers.

From Popular Mechanics
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