This Week in Tech: What on Earth Is a Quantum Computer?

David Bacon, senior software engineer in Google’s quantum lab: Quantum computers do computations in parallel universes. This by itself isn’t useful. U only get to exist in 1 universe at a time! The trick: quantum computers don’t just split universes, they also merge universes. And this merge can add and subtract those other split universes.

David Reilly, principal researcher and director of the Microsoft quantum computing lab in Sydney, Australia: A quantum machine is a kind of analog calculator that computes by encoding information in the ephemeral waves that comprise light and matter at the nanoscale. Quantum entanglement — likely the most counterintuitive thing around — holds it all together, detecting and fixing errors.

Daniel Lidar, professor of electrical and computer engineering, chemistry, and physics and astronomy at the University of Southern California, with his daughter Nina, in haiku:

Quantum computers
solve some problems much faster
but are prone to noise

Superpositions:
to explore multiple paths
to the right answer

Interference helps:
cancels paths to wrong answers
and boosts the right ones

Entanglement makes
classical computers sweat,
QCs win the race

Scott Aaronson, professor of computer science at the University of Texas at Austin: A quantum computer exploits interference among positive and negative square roots of probabilities to solve certain problems much faster than we think possible classically, in a way that wouldn’t be nearly so interesting were it possible to explain in the space of a tweet.

Alan Baratz, executive vice president of research and development at D-Wave Systems: If we’re honest, everything we currently know about quantum mechanics can’t fully describe how a quantum computer works. What’s more important, and even more interesting, is what a quantum computer can do: A.I., new molecules, new materials, modeling climate change …

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