Concepts Of Quantum Computing

Quantum computing is based upon physics completely different from that observed in the electronic devices of today. In today's computing paradigm, a transistor can be in only one of two states called bits - 0 or 1, on or off. But in the realm of quantum computing a transistor can be in a state of 0, 1, or a "superposition" of 0 or 1. And there can be many superpositions. These quantum bits are called "qubits." Physically, qubits are encoded in atoms, photons, ions, or electrons.

Whereas a standard transistor can perform only one operation at a time, a qubit can perform many simultaneously. Therefore a quantum computer containing the same number of transistors as an ordinary computer of today can be a million times faster. A 30-qubit quantum computer could perform as many as 10 teraflops - 10 trillion floating-point operations per second! Today's desktop computers perform gigaflops - billions of operations per second.

So obviously, that's where the interest in quantum computing comes from - speed. A personal computer a million times faster than the one currently on your desk boggles the mind. After all, how fast can you type? But there are applications that would benefit from that type of speed, such as image recognition, cryptography, and other problems that require enormous computing power. Personally, I'd be happy with a computer that's ready to go as soon as you turn it on. I don't anticipate being able to type a million times faster than I already do.

One problem with quantum computing is that if you observe the quantum state of a qubit, it changes. So scientists must devise an indirect method of determining the state of a qubit. To do this, they are trying to take advantage of another quantum property called "entanglement." At the quantum level, if you apply a force to two particles they become "entangled;" a change in the state of one particle is instantly reflected in the other particle's change to the opposite state. So by observing the state of the second particle, physicists hope to determine the state of the first.