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Definition: quantum computing

A computer architecture based on quantum mechanics, the science of atomic structure and function. In the late 1990s, the feasibility of such a computer was demonstrated by MIT, the University of California at Berkeley and Stanford University.

The Computations Can Be Staggering
There are many problems that bog down even the fastest supercomputers. The traveling salesman routing problem is a classic example that seeks to find the most efficient round trip between a number of cities. With 50 cities, the number of possible routes is 63 digits long. Whereas "classical" (non-quantum) computers may take days or even months to solve problems such as these, quantum computers are expected to come up with answers in mere minutes or seconds. See binary values.

Qubit Superposition and Entanglement
Quantum computing uses the "qubit," or quantum bit, comprising one or more electrons, and there are various approaches to their design. Quantum superposition is the condition that allows a qubit to be a 0 and 1 at the same time (see qubit). Entanglement is the property that allows one particle to relate to another over distance.

Quantum annealing and gate level are the two major categories of quantum computers, and there is a lot of rivalry between them.

Quantum Annealing
D-Wave Systems in Canada offers the only commercial "quantum annealing" computer on the market. D-Wave computers are huge, refrigerated machines with up to 2,000 qubits that are used for optimization problems such as scheduling, financial analysis and medical research. Annealing is used to find the optimum route or the most efficient combination of settings to solve a problem.

The D-Wave Chip Is Very Cool
D-Wave's latest quantum annealing chip has 2,000 qubits. The refrigeration assembly is shown without its cover, and the chip is at the bottom. Using liquid nitrogen and liquid helium stages from top to bottom, it keeps getting colder all the way down to minus 459 degrees Fahrenheit. (Images courtesy of D-Wave Systems, Inc., www.dwavesys.com)

Gate Level
Unlike the annealing method, gate level quantum computers use gates similar to classical computers but with vastly different logic. Gate level computers are expected to be used for a wide variety of applications. For example, they can factor huge numbers and should be able to crack cryptographic keys in a matter of seconds, which has menacing implications. Several companies are developing gate level machines, each with different qubit designs.

Intel's 49-Qubit Quantum Computer
In 2018, Intel announced its Tangle Lake gate level quantum chip with a unique architecture of single-electron transistors coupled together. Intel CEO Brian Krzanich is showing the chip at CES 2018. (Image courtesy of Intel Corporation.)

A Lot Different Than Classical Computing
Inventing quantum hardware designs is not the only difficult job. Just as challenging is developing the algorithms that allow the quantum architectures to solve real-world problems, and there are hurdles to overcome with both annealing and gate level methods. However, scientists believe everyday quantum computing is just a matter of time. See also quantum cryptography.

Are We at a Similar Stage?
Quantum computing is in the very early stages of development. When an eight-ton UNIVAC I in the 1950s evolved into a chip decades later, it makes one wonder what quantum computers might look like 50 years from now. See UNIVAC I and microcontroller.