Quantum computers –The next revolution in the information technology of the 21st century?

A word that to most people sounds as scary and bizarre as exciting-and futuristic increasingly makes its way into the sphere of public attention. It combines the apparent technological omnipotence of digital computing with the awe-inspiring complexity and abstractness of the most important theory in 20th century’sphysics:the word is out on the „quantum computer“. And by no means does it refer to the esoteric dreams of miraculous healing and soul cleansing („quantum healing“), spiritual home furnishing („quantum Feng Shui“), the universally perfect love relationship („quantum resonance“), or other nonsense mystics often associated with the word „quantum“, but a potential technological revolution that could shape the 21stcentury as much as conventional computersformed the 20th century.

A few days ago the IT company IBM announced that it will makeits quantum computing technology accessible to the public as a cloud service. Within IBM’s “Quantum Experience“ interested parties may access a 5-qubit computing system though the internet and create and run programs on itby means of a provided programming and user interface. With this IBM expects to accelerate the development of quantum computing technology. Furthermore, a few months ago Google announced that it acquired a quantum computer built by the company „D-Wave“ in order to support Google’s research in that space. Companies like IBM, Google, and Microsoft consider quantum computers as the possible basis for the next generation of supercomputers and claim to have made some significant progress in their development in the recent past.

What makes a quantum computer so special? Do the building blocks of conventional computers not already depend decisively on quantum mechanics(such as the transistor effect)?Indeedthe 20th century’s digital revolution would have been impossible without quantum physics. Nonetheless, the construction and functionality of conventional computers (called the „von Neumann architecture“) is at least in principle possible without quantum effects (and the first computers in the 1940s were made of tubes and capacitors). Quantum physics just allowed the extreme miniaturization of their components which ultimately led to the enormous computational power computers have today. In contrast, quantum computers come with a fundamentally different architecture and functionality, which is already at its core based on the bizarre properties of quantum physics. For storing and processing of information they directly employsubatomic particles and use their quantum properties. This potentially allows quantum computers to achieve a computational speed which is unimaginably higher than the one of today’s computers, and could enable them deal with complexities that still make us cringe in awe today dueto their unpredictability and uncontrollability. A quantum computer could readily crack conventional encryption methods for digital data, quickly sift through massive amounts of data, and solve complex optimization problems, all of which today’s conventional supercomputers will by no means succeed in within any reasonable time. Quantum computer would thus threaten global data security, which makes them not only for the military interesting and at the same time menacing. But they could also be used to work on currently unsolvable problems in physics or quantum chemistry, and they could open up completely new possibilities in various fields from materials research to drug development. However, all this is still purely theoretical, since a functioning universal quantum computer does not exist yet.

But how exactly does a quantum computer work? In contrast to the information units a conventional computer operates with, the „bits“, which can be in two different states, either “1” or “0” (hence the term „digital“), the information unitsin a quantum computer, the so-called „quantum bits“ (short „qubits“), can take on bothof these and all intermediate valuessimultaneously. This is due to the possibilities of quantum systems being in states of „superposition”, i.e. states that in classical termsmutually exclude each other. This bizarre property of quantum objects was once subject of heated discussions among the fathers of quantum physics which found their ultimate expression in the well-known thought experiment of “Schrödinger‘s cat“. Furthermore, in quantum physics differentsingle systems/particles can exist in an inseparable whole, a phenomenon called „entanglement”. It is as if the qubits were coupled to each other by the means of an invisible spring. Via a “spooky distant relationship” they all are in contact with each other, and each qubit knows so to say what the others are up to. Thus, so the hope of the physicist, they can perform operations on all states at the same time, allowing a high degree of parallelization of the calculations and thereby increasing the processingpower of the computer exponentiallywith the number of qubits – compared to a linear increase of computational power with the number of computational units in the sequential processing of a traditional (“von Neumann”) computer.

IBM’s „Quantum Experience“ is based on a processor with five qubits implemented on a silicon chip. The chip requires to be cooled to some minus 270 degrees Celsius, because the data stored on the entangled qubits is extremely sensitive and can be easily damaged by heat or radiation. This reflects a general problem of quantum computers: Entangled quantum states decay very quickly, often too fast to carry out the desired operations without error. With the help of an ultra-low temperature fridge the physicists can prevent that from happening.Furthermore, they have meanwhile developed methods to correct erroneous qubits. According to IBM, operational quantum processors, which consist of 50 to 100 qub its, will be available within a decade. And already a system with 50 qubits is likely to surpass the computational power of any of today’s supercomputers (at least for some important problems).

Also the NSA is working on the development of a quantum computer. Once available it could give the secret service access to the vast amount of confidential data in the banking and financial sector, in the health industry, in government,business and industrial activities, and many other areas. According to the „Washington Post“, which refers to documents of Edward Snowden, the research project on quantum computer is part of an 80 million dollar research program of the NSA. We can only speculate how far the program is advanced. Much of the research program is classified, and there are rumors that the secret services could be significantly ahead of civilian laboratories.

The fact that companies such as IBM or Google decided to now go public with their plans for quantum computer could be a sign that the technology is slowly growing mature enough to be applied to real world problems. Not much is known about quantum computers by a broad audience. But the technological and societal impact they come with is likely totake shape in only a few years. Who knew about quantum physics and the transistor effect in the late 1940s? Quantum computers could thus become one of the key technology drivers of the 21st century, as much as digital processing (“von Neumann”) units were for the 20th century.

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