20 September 2012

Qubit On A Silicon Based Transistor For Quantum Computing Developed

The next evolution in computers is the quantum computer. With quantum computers, processors within utilize properties of atoms as dictated by quantum mechanics.

Classical computers (computers used today) use bits. Bits can be assigned either a 0 state or a 1 state to create a binary code. Using the 0 or 1 state, calculations are performed, information can be processed, and instructions followed.

Quantum computers use a different kind of bit; the qubit. Atoms generate spin, an up-spin and a down-spin, just like a regular computer bit, the up-spin and down-spin is similar to the 0 or 1 state. What makes the qubit special is that it also has a state called Superposition where the qubit is both up and down at the same time.

It is this superposition that makes quantum computing possible. An example would be an instruction to dial one million numbers. The classical computer would go about this by dialing the numbers one at a time. A quantum computer would dial all numbers in one step.

Technology is still far from constructing a practical quantum computer but each day, new developments are bringing it closer and closer to fruition. Early stage quantum computers the size of a room have already been built.

An often used principle when it comes to quantum computing is Moore's law. Moore's Law states that computer processing power continues to double every 18 months. This means that by the year 2030 or earlier, we will find that the circuits on a microprocessor will approach the atomic scale and quantum computing will be the norm.

Single-atom writer a landmark for quantum computing

A research team led by Australian engineers has created the first working quantum bit based on a single atom in silicon, opening the way to ultra-powerful quantum computers of the future.

In a landmark paper published today in the journal Nature, the team describes how it was able to both read and write information using the spin, or magnetic orientation, of an electron bound to a single phosphorus atom embedded in a silicon chip.

"For the first time, we have demonstrated the ability to represent and manipulate data on the spin to form a quantum bit, or 'qubit', the basic unit of data for a quantum computer," says Scientia Professor Andrew Dzurak. "This really is the key advance towards realising a silicon quantum computer based on single atoms."

Video: Quantum Computer Qubit In A Silicon Based Transistor

Dr Andrea Morello and Professor Dzurak from the UNSW School of Electrical Engineering and Telecommunications lead the team. It includes researchers from the University of Melbourne and University College, London.

"This is a remarkable scientific achievement – governing nature at its most fundamental level – and has profound implications for quantum computing," says Dzurak.

Dr Morello says that quantum computers promise to solve complex problems that are currently impossible on even the world's largest supercomputers: "These include data-intensive problems, such as cracking modern encryption codes, searching databases, and modelling biological molecules and drugs."

The new finding follows on from a 2010 study also published in Nature, in which the same UNSW group demonstrated the ability to read the state of an electron's spin. Discovering how to write the spin state now completes the two-stage process required to operate a quantum bit.

The new result was achieved by using a microwave field to gain unprecedented control over an electron bound to a single phosphorous atom, which was implanted next to a specially-designed silicon transistor. Professor David Jamieson, of the University of Melbourne's School of Physics, led the team that precisely implanted the phosphorous atom into the silicon device.

UNSW PhD student Jarryd Pla, the lead author on the paper, says: "We have been able to isolate, measure and control an electron belonging to a single atom, all using a device that was made in a very similar way to everyday silicon computer chips."

As Dr Morello notes: "This is the quantum equivalent of typing a number on your keyboard. This has never been done before in silicon, a material that offers the advantage of being well understood scientifically and more easily adopted by industry. Our technology is fundamentally the same as is already being used in countless everyday electronic devices, and that's a trillion-dollar industry."

The team's next goal is to combine pairs of quantum bits to create a two-qubit logic gate – the basic processing unit of a quantum computer.

More on quantum computers can be found here: Quantum Computers: Tomorrows Technology


University of New South Wales
University of Melbourne
University College, London
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