A computer architecture based on quantum mechanics, the science of atomic structure and function. Quantum computing is radically different from ordinary computers ("classical computing"). It can only solve certain problems, all of which are mathematically based and represented as equations. Quantum computer processing emulates nature at the atomic level and one of its more auspicious uses is the analysis of molecular interactions to uncover nature's mysteries.

In the late 1990s, the feasibility of quantum computing was demonstrated by MIT, the University of California at Berkeley and Stanford University. Because of the high cost of building and maintaining quantum computers, quantum computing is likely to be offered more as a cloud service than machinery for sale to individual companies. Time will tell. See quantum mechanics.

**Computations Can Be Staggering**

There are many problems that bog down even the fastest supercomputers because numbers tend to grow faster than one might imagine. An easy one to understand is the classic traveling salesman problem, which attempts to find the most efficient round trip between cities. The first thing is to compute all the possible routes, and if the trip involved 50 cities, the result is a number 63 digits long. Whereas classical computers may take days or even months to solve such problems, quantum computers are expected to have 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 in multiple states at the same time (see qubit). Entanglement is the property that allows one particle to relate to another over distance.

Gate model and quantum annealing are the two major categories of quantum computer architectures.

**Gate Model QC**

Gate model quantum computers use gates similar in concept to classical computers but with vastly different logic and architecture. Several companies are developing gate model machines, including Google, IBM, Intel and Rigetti, each with different qubit designs. The quantum chip is programmed by sending microwave pulses to the qubits. Digital-to-analog and analog-to-digital conversion takes place at the QC chip.

**IBM's Q Experience in the Cloud**

In 2016, IBM made a 5-qubit gate model quantum computer available in the cloud to allow scientists to experiment 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.

**IBM Q - Gate Model**

**Intel 49-Qubit Quantum Computer**

**Quantum Annealing**

D-Wave Systems in Canada offers the only "quantum annealing" computer. 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.

**D-Wave Chips Are Cool Too**

**The Algorithms Are Critical**

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 gate model and annealing methods. However, scientists believe everyday quantum computing is inevitable.

**A Potential Catastrophe**

Eventually, quantum computers are expected to factor huge numbers and should be able to crack cryptographic keys in a matter of seconds. Scientists contend it is only a matter of time before this becomes a reality. When it does, it has menacing implications as every encrypted transaction as well as every cryptocurrency system in the world will be vulnerable to hacking unless quantum-safe methods are instituted beforehand. See quantum secure.

**Are We at a Similar Stage?**

There are many problems that bog down even the fastest supercomputers because numbers tend to grow faster than one might imagine. An easy one to understand is the classic traveling salesman problem, which attempts to find the most efficient round trip between cities. The first thing is to compute all the possible routes, and if the trip involved 50 cities, the result is a number 63 digits long. Whereas classical computers may take days or even months to solve such problems, quantum computers are expected to have answers in mere minutes or seconds. See quantum supremacy, binary values and rice and chessboard legend.

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 in multiple states at the same time (see qubit). Entanglement is the property that allows one particle to relate to another over distance.

Gate model quantum computers use gates similar in concept to classical computers but with vastly different logic and architecture. Several companies are developing gate model machines, including Google, IBM, Intel and Rigetti, each with different qubit designs. The quantum chip is programmed by sending microwave pulses to the qubits. Digital-to-analog and analog-to-digital conversion takes place at the QC chip.

In 2016, IBM made a 5-qubit gate model quantum computer available in the cloud to allow scientists to experiment 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.

D-Wave Systems in Canada offers the only "quantum annealing" computer. 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 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 gate model and annealing methods. However, scientists believe everyday quantum computing is inevitable.

Eventually, quantum computers are expected to factor huge numbers and should be able to crack cryptographic keys in a matter of seconds. Scientists contend it is only a matter of time before this becomes a reality. When it does, it has menacing implications as every encrypted transaction as well as every cryptocurrency system in the world will be vulnerable to hacking unless quantum-safe methods are instituted beforehand. See quantum secure.

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