The hyperbole surrounding quantum
computers has steadily increased over the 30-plus years since Richard Feynman
proposed the idea. But what exactly is a quantum computer?
A conventional computer uses on-off
switches to store information. On equals one, and off equals zero. With those
two digits, any type or amount of information can theoretically be stored and
manipulated using a binary counting system.
A quantum computer employs the quantum
mechanical properties of atomic and sub-atomic particles to do the same thing.
When an electron is put in the presence of a magnetic field, it spins. If the
direction of the field is flipped, the electron reverses the direction of its
spin. This directionality of these so-called Q-bits, which is referred to as
up spin or down spin, can be used exactly like the on-off state of a transistor
in a conventional computer.
According to an article in Fortune1 magazine, a quantum
computer’s up-down electrons, however, can be both off and on at the same
time — or anything in between. The term used to describe this effect is
“superposition.”
As the number of Q-bits rises, their
ability to store data grows exponentially. For example, if you wanted to have
the same power as a quantum computer with just 300 Q-bits, you would need to
equip a classical computer with transistors equal to the number 10 raised to
the 90th power. That could not be done, since there are not even that many
atoms in the entire universe.
This mind-boggling potential holds out
the promise of a massively parallel computer that could do an almost infinite
number of calculations simultaneously, even while the device remained extremely
small.
It is common in the popular press to say
that quantum computers will be able to solve exceptionally difficult
mathematical problems, including those known as NP-complete problems. An
example of an NP-complete problem is forecasting the weather. Even with
today’s most sophisticated technology, we can’t predict the weather very well.
That’s because predicting the weather accurately would require calculating the
state of every molecule of air and water in any weather system and projecting
out to...
