But so far, qubits have proven too fragile to function reliably in larger groups,
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perform any computation a classical computer would.
“As we push on the number of qubits, you’re able to explore a much more varied
set of quantum circuits,” says Jerry Chow, the senior manager of the
Experimental Quantum Computing Group at IBM. If only it were that simple.
The “lossy qubit” problem, as Chow puts it, means that parts of each quantum
computer that exists today are dedicated just to resolving errors in their
computations, instead of performing the computations themselves. The
quantum volume of a computer, a numerical value that describes its maximum
potential to perform calculations, is always less than the number of qubits it
contains. Likewise, the number of photons that begin their journey intact at the
beginning of a journey through a test loop is always greater than the number
that return.
To circumvent this problem and unlock the full potential of quantum
computing, some researchers are working on adding error-correcting codes,
which are already implemented in some classical computers. Others are
exploring alternative methods of applying quantum physics to computing that
don’t involve gates and circuits. One possibility is tricking quantum particles
into ignoring background noise—vibrations, temperature changes, and stray
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University of Chicago team announced in August that they had successfully
performed this kind of trickery in a limited experiment.
Quantum annealing is another technique with potential. It involves harnessing
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through gates in a circuit. Some commercially available quantum computers
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algorithms, like those based on the “traveling salesman” problem, which seeks
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D-Wave’s approach in an experiment last year to help buses in Lisbon, Portugal,
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limited to taking attendees of a technology conference from the airport to the
convention center.