Quantum Not Gate

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Mooij and co-workers created the quantum version of a basic building block of computer logic, called the controlled-not (CNOT) gate, which switches a bit from 0 to 1 or vice versa if a second bit is set to 1-or does nothing if that bit is set to 0. "You need something like a controlled-not gate to make every quantum algorithm you might need," Mooij says. Their gate, described in this week's Nature, consisted of two side-by-side loops of aluminum cooled to a few kelvins (nearly -459 degrees Fahrenheit). A current flowing around one loop created a magnetic field that influenced the current flowing around the second loop.