Thursday, April 4, 2013

Quantum Computing

Computing world always fascinated me. That’s why I did my engineering in Electronics and Communication. I learnt about the microprocessors and learnt about how data transfer so fast from digital circuits.
But today Computing is no longer about transistor based microprocessors. Here comes the Quantum Computing now. Today, over 400 million transistors have been placed in a single microprocessor, thanks to VLSI or very large scale integration process and its development over the. But, today scientists realize that we do not want more transistors in a single microprocessor, rather we want superior computing experience. So, scientists are trying to develop a computer based on quantum mechanical phenomena such as superposition and entanglement to perform operation on data. This principle was first proposed by Richard Feynman in 1982.

Faster and convenient
Fundamentally, a quantum computer works on qubits whereas today’s computer works on bits. A single bit can be in a state of 1 or 0, where 1 means positive and 0 means negative. These arrangements of bits give a computer ‘on’ or ‘off’ state, and similarly programs on modern day computers which are also known as the binary system, work on following the same principle. But ‘qubits’ can represent 0, 1 and quantum superposition of various combinations. Thus, two qubits can represent 4 different states and three qubits can represent 8 different states i.e. n qubits can represent an arbitrary superposition of 2n different states simultaneously, whereas a modern transistor based computer can represent any one of this 2state on any given time. So, theoretically it is possible to work extremely faster using quantum computer, almost at the speed of light. Thus, a quantum computer can work on all the 2numbers parallel which the present binary system cannot do. Though one may not be able to boost performance while working on word processing or internet browsing, but when one tries to work on cryptography, scientific problems, indexing a huge database, then the real power of a quantum computer can be achieved.
Quantum Dots model
One cannot build a quantum computer using today’s technology, a technology which will enable the existence of qubits in its coherent superposition state. So far no possible model has come out for the quantum computer, but there are various models on which researchers are working on building a quantum computer model. Quantum Dots is one such model where a single electron is trapped inside a cage of atoms. A controlled laser with proper frequency will come and excite the electron and a second burst of laser causes the electron to go to its ground state. The excited state can be defined as 1 and the ground state can be defined as 0 and the controlled laser light work as a NOT gate. If the pulse of laser light is emitted only for half the duration of the NOT function as stated earlier, then the electron will achieve the superposition of both the excited and the ground state and it will achieve the coherent state of the qubits. Using different arrangement of Quantum Dots one can create different logical function and work on them. Quantum dot is one of the main popular models though it has its share of concern. Electron will only achieve the excited state for few microseconds before it goes to the ground state. Constructing the Quantum Dots is very difficult as the size of the Dots is only 1 nanometer. To achieve the superposition and the coherent stage, Quantum Dots need laser of different frequencies and wavelength. This type of technology is difficult to achieve and costly.
Computing liquid
According to a new development and theory, a new building block theory has emerged. As per this model, quantum medium has to be very small and isolated from its surrounding. When a magnetic field is applied to this medium, the electron will start spinning in different directions and this depicts the different state of the qubits. If it starts moving upward, then it will depict 1, and if it will start moving downward, then it will depict 0. Nuclear Magnetic Resonance or NMR can be used to control the spin to get superposition and coherent states of the qubits. In this model, the nucleus of the single molecule works as the qubits and a group or ‘mug’ of the molecules working together. The advantage is that though there is the possibility of crashing with one another but the spin of the nucleus remain unchanged during this process, and thus all the states and coherent superposition will not get affected. Also, the molecules will not go to their ground state so quickly and thus allows researchers to perform a few thousands operations quickly.
Quantum programming
Quantum programming will open a complete new way of programming to the developers. This will help to solve extremely complex problems such as factorizations of large numbers, indexing of large databases very fast. With this application and new way of programming animation industry, gaming industry, image editing industry and 3D applications will get huge benefit as modern day computers are not able to process complex algorithms faster.
Artificial Intelligence
As humans, we have our emotions and own mind to think, feel and make decisions. But machines cannot do that. But, with quantum computing, every piece can be logically given to the humanoid and with the large, complex program, and with extremely faster processing power, the machines can also make different decisions and all this can be achieve with the help of quantum computing. Every physical object from a sand dust to the entire universe is guided by set of rules and principle. We may compare them as Quantum Computers. Considering this phenomena, brain of a human can be considered as a computer and consciousness as the computing power. As per Church-Turing principle, every computer is functionally equivalent and that any given computer can simulate other, therefore, it must be possible to simulate conscious rational thought using qubits as it can exist in different coherent states simultaneously.
Computational complexity theory
Quantum computers are able to solve ‘bounded, error, quantum, polynomial time” problems or BQP with probabilistic approach to get the correct answer. Probability of getting the correct answer is very high as compared to the modern day computer. The time taken to compute is half of the time. This way with BQP, quantum computer can take decisions almost in an instant.
Quantum de-coherence
Qubits are highly controlled but they tend to go the ground state or to a de-coherent state quickly, within nanoseconds to milliseconds. This may create errors while computing large numbers or processing complex data as error rates are directly proportional to ratio of operating time with de-coherence time. This requires gates to operate at a faster rate so that qubits can process before their ground state achieved.
As the quantum computers hold a great potential to resolve the entire complex scientific problem, both the private sector and the government are interested in this technology. Quantum computing is still in its nascent stage but with technical advancement we may see a proper quantum computer within next ten years.

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