Sabato, 22 Ottobre, 2016

Researchers achieve record 10-fold stability for quantum computers

Quantum computers: 10-fold boost in stability achieved UNSW obtains 10-fold boost in quantum computing stability
Carmela Zoppi | 19 Ottobre, 2016, 22:46

In the image, the microwave antenna is purple.

Australian scientists have made a breakthrough in quantum computing research by succeeding in developing a new type of quantum bit (qubit) that is able to stay in a stable superposition for 10 times longer than ever previously achieved.

While some researchers focus on using microwave signals, controlling photons, and even electron holes, the team from the University of New South Wales (UNSW) dabbled in silicon atoms.

The paper, entitled "A dressed spin qubit in silicon" is published in the journal Nature Nanotechnology.

"We have created a new quantum bit where the spin of a single electron is merged together with a strong electromagnetic field", says researcher Arne Laucht.

"This quantum bit is more versatile and more long-lived than the electron alone, and will allow us to build more reliable quantum computers", Laucht says.

Its speed and power lie in the fact that quantum systems can host multiple "superpositions" of different initial states, which in a computer are treated as inputs which, in turn, all get processed at the same time.

"The team had already claimed a longevity record - by encoding quantum information in the spin of a phosphorus atom in a silicon chip, in a static magnetic field".

But by subjecting a single atom in silicon to a very strong, continuously oscillating electromagnetic field at microwave frequencies, the researchers were able to extend the preservation of the superposition for 10 times longer than a standard qubit.

This process allows the qubit to remain in a superposition state for ten times longer than has previously been achieved. This means that we can vastly expand the kinds of ultra-fast calculations that quantum computer can perform.

According to Morello, the qubit can be controlled in a variety of ways which would be impractical with an "undressed" qubit. For example, he suggested that the qubit could be controlled by modulating the frequency of the microwave field, like an FM radio.

"In some sense, this is why the dressed qubit is more immune to noise: the quantum information is controlled by the frequency, which is rock-solid, whereas the amplitude can be more easily affected by external noise". To achieve this, the UNSW team constructed a device, known as a quantum logic gate, that allows for calculations to be performed between two quantum bits, or 'qubits.' This completes the physical components needed to realize super powerful silicon quantum computers. Matching the Commonwealth Bank's efforts, Telstra also pledged AU$10 million over five years, to boost UNSW's capacity to develop the world's first silicon-based quantum computer.

Although now quantum computers are merely a concept, numerous computer science researchers around the world and billions of dollars have been invested to create them, and it is believed that these new super-powerful computers will be available within the next 50 years. That includes searching extremely large databases or modelling complex systems such as biological systems or chemical components for medical research.

Last week, Morello was named inaugural recipient of the Rolf Landauer and Charles H. Bennett Award in Quantum Computing by the US-based organisation of physicists, the American Physical Society, for his "remarkable achievements in the experimental development of spin qubits in silicon".

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