Quantum Computing
The Phosphorous Atom Quantum Computing Machine

With the increasing amounts of data in the world, the need for finding ways to store and process the information has become a necessity. To perform this activity, the conventional systems store and operate the information in binary form. Moving beyond the binary system to provide a much more powerful information platform than traditional computers gave rise to quantum mechanics.

NucleusIn quantum mechanics, the most popular unit of quantum information is the qubit, a two-level quantum system. Quantum information varies from the classical information in several aspects and its processing completely uses qubits as its basic information units.

Efforts to build a quantum computer are going on since many years and about a decade back, a physicist, Professor Bruce kane in Australia put forward a design for a quantum computer. The design suggested that phosphorus atoms fixed in silicon would be the best way to store and manipulate quantum information.

Kane predicted that the nucleus of the phosphorus atom could store a single qubit for long time and by using well-known techniques from nuclear magnetic resonance spectroscopy, a magnetic field could easily address this qubit allowing single-qubit manipulations. But because the nuclear spins do not interact each other, two-qubit operations are not possible.

In order to enable the two-qubit operations, Prof.kane suggested transferring spin to an electron moving the phosphorus atom which would communicate easily with an electron orbiting a nearby phosphorus atom. By this, two-qubit operations would be possible by manipulating the two electrons with electric fields.

As each atom could be considered individually utilizing the standard electronic circuitry, the size of the computer can be increased by adding more atoms along with their associated electronic equipment and then connect it to a conventional computer.

About 100 researchers of Australia have been working to build a kane quantum computer. They made some significant breakthroughs such as inserting phosphorus atoms at precise locations in silicon with the help of tunneling microscope. Using powerful magnetic fields, they have also been able to address the nuclear rotations of the phosphorus atoms.

But the challenge was to find a way to address the spin of an individual electron orbiting a phosphorus atom and to estimate its value. The researchers from the University of New South Wales in Sydney solved this problem.

By implanting a single phosphorus atom in a silicon nano-structure and placing it in a powerful magnetic field at a temperature close to absolute zero, the scientists were able to flip the state of an electron orbiting the phosphorus atom by moving it with microwaves. The final step was to read out the state of the electron using a process known as spin-to-charge conversion.

The ultimate result is a device that canĀ  store and manipulate a qubit which has the potential to perform two-qubit logic operations, thus making it a good platform to develop a scalable quantum computer.

The main advantage of this Australian design is that it is compatible with the existing silicon-based chip-making industry. Although, it is years away from emerging from the labs, this technology can be incorporated into future chips.

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