Researchers at the University of California, Santa Barbara, have become the first to combine a quantum processor with memory that can be used to store instructions and data. This achievement in quantum computing replicates a similar milestone in conventional computer design from the 1940s.

Although quantum computing is now mostly a research subject, it holds out the promise of computers far more capable than those we use today. The power of quantum computers comes from their version of the most basic unit of computing, the bit. In a conventional computer, a bit can represent either 1 or 0 at any time. Thanks to the quirks of quantum mechanics, the equivalent in a quantum computer, a qubit, can represent both values at once. When qubits in such a "superposition" state work together, they can operate on exponentially more data than the same number of regular bits. As a result, quantum computers should be able to defeat encryption that is unbreakable in practice today and perform highly complex simulations.

Linking a processor and memory elements brings such applications closer, because it should make it more practical to control and program a quantum computer can perform, says Matteo Mariantoni, who led the project, which is part of a wider program at UCSB headed by John Martinis and Andrew Cleland.

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