FROM BITS TO QUBITS
Conventional computers are built from silicon chips that contain millions or billions of miniature transistors. Each of these can be turned "on" or "off" to represent a value of either "1" or "0". Conventional computers subsequently store and process data using "binary digits" or "bits". In contrast, quantum computers work with "quantum bits" or "qubits". These are represented in hardware using quantum mechanical states rather than transistors that are turned "on" or "off". For example, quantum computers may use the spin direction of a single atom to represent each qubit, or alternatively the spin direction of a single electron or the polarization orientation of a photon. Yet other quantum computing designs supercool rare metals to allow qubits to be represented by the quantum spin of a tiny magnetic field.
Due to the peculiar laws of quantum mechanics, individual qubits can represent a value of "1", "0" or both numbers simultaneously. This is because the sub-atomic particles used as qubits can exist in more than one state -- or "superposition" -- at exactly the same point in time. By attaching a probability to each of these states, a single qubit can therefore process a wide range of values. In turn, this allows quantum computers to be orders of magnitude more powerful than their conventional, purely digital counterparts.
The fact that qubits are more "smears of probability" than definitive, black-and-white certainties is exceptionally weird. Flip a coin and it cannot come up both heads and tails simultaneously, and yet the quantum state of a qubit can in some senses do just that. It is therefore hardly surprising that renowned nuclear physicist Niels Bohr once stated that "anyone who is not shocked by quantum theory has not understood it!"
Another very bizarre thing is that the process of directly observing a qubit will actually cause its state to "collapse" to one or other of its superpositions. In practice this means that, when data is read from a qubit, the result will be either a "1" or a "0". When used to store potentially infinite amounts of "hidden" quantum data, qubits can therefore never be directly measured. This means that quantum computers need to use some of their qubits as "quantum gates" that will in turn manipulate the information stored and processed in other hidden qubits that are never directly measured or otherwise observed.
Because qubits can be used to store and process not just the digital values of "1" and "0", but also many shades of grey in between, quantum computers have the potential to perform massively parallel processing. This means that quantum computers will be very effective at performing tasks -- like vision recognition, medical diagnosis, and other forms of artificial intelligence processing -- that can depend on very complex pattern matching activities way beyond the capabilities of both traditional computers and most human beings.
OK, so quantum computing may sound all very theoretical (and indeed at present a lot of it actually is!). However, practical quantum computing research is now very much under way. For a start, back in 2007 a Canadian company called D-Wave announced what it described as "the world's first commercially viable quantum computer". This was based on a 16 qubit processor -- the Rainer R4.7 -- made from the rare metal niobium supercooled into a superconducting state. Back in 2007, D-Wave demonstrated their quantum computer performing several tasks including playing Sudoku and creating a complex seating plan.
Many people at the time were somewhat sceptical of D-Wave's claims. However, in December 2009, Google revealed that it had been working with D-Wave to develop quantum computing algorithms for image recognition purposes. Experiments had included using a D-Wave quantum computer to recognise cars in photographs faster than possible using any conventional computer in a Google data centre.
In 2011, D-Wave launched a 128-qubit quantum computer. Called the D-Wave One, this was described by the company as a "high performance computing system designed for industrial problems encountered by fortune 500 companies, government and academia". The first D-Wave One was sold to US aerospace, security and military giant Lockheed Martin in May 2011.
By 2013, D-Wave has developed a 512 qubit quantum computer called the D-Wave Two, which was supplied to NASA, Google and the Universities Space Research Association (USRA) to in order to allow the establishment of the Quantum Artificial Intelligence Lab (QuAIL) at the Ames Research Center in California. In January 2017, D-Wave then announced a 2,000 qubit quantum computer -- the D-Wave 2000Q, the first customer for which was Temporal Defense Systems.
D-Wave aside, another major player in quantum computing is IBM. Here a quantum system called IBM Q has been developed, which anybody can now experiment with online. In case you are interested, the basic user guide is here.
Quantum computing is a highly complex and bewildering field with incredible potential (though so too was microelectronics in the 1970s and we all now take that for granted!). For a far more technical overview of the topic, try reading this overview from Stanford University. You may also want to visit the Australian Centre of Excellence for Quantum Computation and Communication Technology. Do be aware, however, that delving into these resources may well make your head hurt!
Ultimately, few companies and individuals will ever own a quantum computer. Nevertheless, within a decade or two many of us could regularly be accessing quantum computers from the cloud. Not least this is because one of the first mainstream applications of quantum computing will be in online security and data encryption. Today, all online security systems rely on prime number calculations that quantum computers are potentially very good at indeed. Fairly soon, anybody with a quantum computer will therefore theoretically be able to use it to crack the security on any bank account or cloud computing resource. The only way to prevent this will be to protect and encrypt all online resources with quantum security gateways. The demand for every bank and cloud provider to invest in a quantum computer -- if only for encryption purposes -- is therefore likely to skyrocket once the technology moves beyond its currently rather costly and cumbersome experimental phase.
Another major application area for quantum computing will be in the processing of Big Data. As the volume of digital data produced on Planet Earth continues to grow expotentially, so a significant potential exists to generate business and social value via its insightful interlinkage. While technologies like Hadoop are currently permitting advancements in the processing of vast data sets, it may well be the development of quantum computers that really pushes large-scale Big Data analysis into the mainstream.
For more information on quantum computing, you may like to watch my Quantum Computing Video. Information on a range of other future technologies can also be found on our sister site ExplainingTheFuture.com.