The final motiviation for building quantum computers is certainly the most fundamental: sheer curiosity.
Scott Aaronson, professor at the University of Texas at Austin, said in his Ph.D. thesis, back in 2004:
For me, quantum computing matters because it combines two of the great mysteries bequeathed to us by the twentieth century: the nature of quantum mechanics, and the ultimate limits of computation. It would be astonishing if such an elemental connection between these mysteries shed no new light on either of them.
Quantum computing and quantum information owe their origins in part to the dissatisfaction with an apparent contradiction between the quantum mechanics of the first half of the twentieth century and special relativity, which limits the movement of any physical object to the speed of light. This worried Albert Einstein, Boris Podolsky and Nathan Rosen, who proposed a thought experiment highlighting the fact that two quanta seem to communicate with each other instantaneously, regardless of distance. In the 1960s, John Bell proposed a statistical test for whether this can happen.
Quantum computing proper began as a purely intellectual exercise in the 1980s, with important thinkers such as Richard Feynman, David Deutsch, Paul Benioff, and Charles Bennett striving to understand how the equations that govern our universe affect what can and cannot be computed efficiently.
At the same time, experimental physicists such as David Wineland, Serge Haroche, Alan Aspect and a host of others were pushing the boundaries of our ability to control and manipulate individual atoms, electrons, photons and tiny amounts of electrical current. They built exquisitely precise atomic clocks and other measurement apparatuses to test theoretical predictions about fundamental physics, then turned their attention to determining how to build a quantum computer.
Thanks to Bell’s theory and an increasingly rigorous set of experiments that confirm its truth, we now understood that information cannot travel faster than light. The exact resolution of why and how Einstein’s “spooky action at a distance” arises is an open topic in the foundations of quantum mechanics, but we will learn more about this quantum entanglement later in this course.
Thus, we can say that building a quantum computer is also a fascinating and important scientific experiment in its own right. It would be surprising if we learned nothing new in the process!
© Keio University