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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. See quantum mechanics.

The Computations Can Be Staggering
There are many problems that bog down even the fastest supercomputers because the number of computations are so staggering. The traveling salesman route is a classic example that seeks to find the most efficient round trip between 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 quantum supremacy, binary values and rice and chessboard legend.

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 model 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. See superconductor. (Images courtesy of D-Wave Systems, Inc., www.dwavesys.com)

Gate Model
Unlike the annealing method, gate model quantum computers use gates similar in concept to classical computers but with vastly different logic and entirely different architecture. Several companies are developing gate model machines, each with different qubit designs. The gates are actually created in real time by sending microwave pulses to the qubits. Gate model computers are expected to be able to factor huge numbers and should be able to crack cryptographic keys in a matter of seconds. This has foreboding implications if an attacker or enemy gains access to the technology.

IBM Q Experience in the Cloud
In 2016, IBM made a 5-qubit gate model quantum computer available in the cloud to allow scientists the opportunity of experimenting with gate model programming. A year later, the open source Qiskit development kit and a second machine with 16 qubits were added. The IBM Q Experience includes a library of educational materials.

The Gate Model IBM Q
Like the D-Wave computer, superconducting materials are used that must be kept at subzero temperatures, and both photos show the covers removed to expose the quantum chip at the bottom. (Image courtesy of IBM Research, www.research.ibm.com)

Intel's 49-Qubit Quantum Computer
In 2018, Intel announced its Tangle Lake gate model 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 is a whole lot different than ordinary computers. The algorithms for solving real-world problems must be invented first, because new algorithms influence the design of the next generation of quantum architecture. There are hurdles to overcome with both annealing and gate model 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.