In the third and final chapter of this series, I explain how one can build a quantum computer in the 21^{st} century in order to accommodate massive applications and large number crunching. Such a computer is paramount to handling big data across the globe, as well as addressing other quantum computing issues.

**Building a Quantum Computer**

- We still don’t know how to build a quantum computer. One huge problem is the particles used for calculations must remain in isolation from their surroundings. Because of the consequences created by entanglement, interactions with outside particles could result in faulty results.

- Quantum physicists are working on a number of methods for controlling qubits: atoms or charged ions in an electro-magnetic trap, nuclear magnetic resonance, superconductor microcircuits, quantum dots, atom conveyors and cavity quantum electrodynamics, among others.

- Quantum computing is still largely theoretical and there is no agreement on the best way to build a quantum computer. We don’t know what a quantum computer capable of complex computing will look like — or even if it is actually possible to build one. We have just begun the journey. We do know whatever the computing device we are using by the mid-century, it will be far more powerful than the computers we use today, just as today’s machines greatly overshadow their predecessors.

**Appendix I: Diagram of a Quantum Computer **(Source: USA Today)

**Other Descriptions of Quantum Computing**

**George Johnson, A Shortcut Through Time: The Path To The Quantum Computer, Alfred A. Knopf: 2003. **

“In the tiny spaces inside atoms, the ordinary rules of reality … no longer hold. Defying all common sense, a single particle can be in two places at the same time. And so, while a switch in a conventional computer can be either on or off, representing 1 or 0, a quantum switch can paradoxically be in both states at the same time, saying 1 and 0…. Therein lies the source of the power.”

**Jakob Reichel,” “Atom Chips,” Scientific American, February 2005: Vol. 292, Issue 2.**

“Today’s star in the quantum scene is the quantum computer. This future device would exploit the superposition principle (another peculiar feature of the quantum world) to carry out certain types of computations much faster than any classical computer could do. A quantum computer functions by manipulating qubits, the quantum counterparts to bits. An ordinary, classical (non-quantum) logical bit can only be true or false, 1 or 0. The qubit, by contrast, can be in a superposition state corresponding to any mixture of true and false at the same time, like Schrödinger’s cat in its mixture of alive and dead.”

In a classical computer, computations corresponding to different bit states must be carried out one after the other. With qubits, they are elegantly performed all at the same time. It has been proven that for certain problems this feature makes a quantum computer fundamentally faster than any classical computer can ever be.

The favorite occupation of quantum physicists these days is to think of practical ways to make a quantum computer: with trapped ions, with large molecules, with electron spins–or maybe with BECs on atom chips. The idea is tempting because such a quantum chip seems so attractively similar to a traditional microelectronics chip, yet at the same time so radically new. Components such as the atom conveyor could be used to bring qubits together to interact in a controllable fashion.

**Aaron Ricadela, “Quantum’s Leap,” InformationWeek, May 10, 2004.**

“Thus, the condensate on a chip is the beginning of a story. As so often occurs in science, the plot of the story is not known in advance, and the actors themselves are discovering it in little steps. As in the past, surprises will crop up–pleasant and unpleasant ones. Some obstacles will be removed; others will force researchers to change directions. Whatever we find out will help to bring the classical and quantum worlds still closer together on the stage of science.”

Dr. Eslambolchi

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