We often talk about computers becoming faster and smaller. As suggested my Moore’s law (given by Gordon Moore, founder of Intel), the number of transistors in an Integrated Circuit will double approximately after two years. Today’s average processors, like the Quad Core Intel Core i7 (Haswell-E, 2014) with a GPU consists of 1.4 billion transistors fabricated using a 22 nm process. We have achieved as much as 2.6 billion transistors in an almost micro-sized package being widely sold in the market. But there is a limit to how many transistors we can load onto a fixed area of silicon — which means after a few years, computers will need to get larger to accommodate more and more transistors.
But that might be a problem. Technology has enabled us to do so much today, and we are obviously going to expect it to perform even more complex tasks in the future. Luckily, quantum computers might hold the solution to this problem. Using the concept of superposition from quantum mechanics, computers in the future might be able to work a hundreds of times faster than today’s computers.
Let me first give you an idea about a classical computers’ (today’s computers) working: each transistor can be in a ‘on’ state, when it conducts electricity, or an ‘off’ state, when it doesn’t. A combination of ‘on’ aka. ‘1’ and ‘off' aka. ‘0’ defines every operation of a computer. The greater the number of transistors, the greater the on and off states and the more the combinations of these 1,0 binary states - all leading to faster, more powerful computers.
The quantum computer has a trick up its sleeve: using ‘qubits’. Just like classic computers are based on ‘bits’, i.e. 1 and 0, quantum computers use ‘qubits’, which can hold the values 1, 0 and any superposition between the two. Didn’t understand? Read on.
Quantum computers are based on the superposition states of qubits (atoms, ions, subatomic particles etc.). A qubit can be ‘excited' or 'not excited' or ‘both', but when observed, only one of the two ‘excited’ or ‘not-excited’ are seen. This is because in the process of observation, external energy transfers cause change in state of the qubit. In order to “see” the intermediate states, the quantum mechanical concept of entanglement is used, in which an external atom can be “entangled” or copied to the actual qubit atom required to be observed by applying certain force. Only then can the observation happen, and the computer work.
This may not be the perfect explanation, so I highly recommend you watch this video to understand the concept better...
But what does all this science mean? Consider it in this analogy: A classical computer is a two-dimensional calculator, with a 1 or a 0 axis. A quantum computer has a third dimension - the superposition between 1 and 0, so it can be considered as a 3D calculator. Now, while a classical computer will solve problems ‘one layer’ at a time (since it is 2D), a quantum computer can solve multiple layers having the same 1 and 0 constants. This increases the performance of quantum computers by many manifolds.
Because a Quantum Computer runs on multiple states and not just 1 and 0, it can complete a million calculations in the same time a classic computer takes to complete one. A 30-qubit quantum computer is equivalent to a 10 teraflops of computing power - as compared to a few gigaflops of today’s average computers.
Quantum computers are still in their infancy, but they might be in considerable existence in the next few decades. Most of the work done on quantum computing is theoretical, but Canadian company D-Wave, along with minds from Google and NASA, built a quantum computer to solve complex mathematical equations, and ask the most challenging optimisation problems.
The D-Wave 2X, which is the latest D-Wave computer with 1000+ qubits, uses the technique of quantum annealing to finding the global minimum of a function (think about it as the cheapest way to travel 20 cities -taking into consideration hundreds of variables like ticket prices, flights, time duration etc.). The computer operates at almost absolute zero temperature, at 15 miliKelvin or -273.135 degrees celsius. The processor is just thumb-sized, but with the refrigerator, the system is the size of a large server.
This computer outperforms classical computers in solving hard optimisation problems by a factor of a 2 to 600 times (source). But the D-Wave computer is not a perfect quantum computer because of its inability to solve certain quantum mathematical equations faster than classical computers. The computer doesn’t show the “quantum speedup” expected out of a quantum computer.
Whatever be the case, there is a lot to expect from quantum computers. There are many researchers and companies like Google and Microsoft working to develop quantum computing systems that offer a significant performance boost from already existing supercomputers, while reducing error rates in observing qubits and running more stable systems. Only time will tell when quantum computers will replace modern supercomputers and eventually make their way to the general public.
Until then, we can only wonder what’s possible using quantum computers. "Are we alone in this universe?" might just have a valid answer in the coming years!
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