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#Quantum computers take a leap forward after scientists build qubit logic gate on silicon chip A major step towards building quantum computers capable of performing formidable calculations at a fraction of the speed of current machines has been achieved. Computer scientists claim to have made a'game-changing leap'by building a logic gate a building block of a digital circuit using the strange properties of subatomic particles in silicon. They say these could eventually lead to new types of quantum microchips that would revolutionise the digital world. Quantum computing takes advantage of the ability of subatomic particles to exist in more than one state at any time. For example a photon can appear as both a wave and a particle. In traditional computers available today, data is expressed in one of two states known as binary bits which are either a 1 or a 0. A quantum bit, or qubit as it is known, can exist in both of these states at once, meaning many computations can be performed in parallel. For example, two qubits can encode four different values while a three qubit system encodes eight different values. This would allow new types of computers to be constructed that would far surpass the capabilities of modern super computers. Professor Andrew Dzurak director of the Australian National Fabrication Facility at the University of New south wales, said:''We've demonstrated a two-qubit logic gate-the central building block of a quantum computer-and, significantly, done it in silicon.''Because we use essentially the same device technology as existing computer chips, we believe it will be much easier to manufacture a full-scale processor chip than for any of the leading designs, which rely on more exotic technologies.''This makes the building of a quantum computer much more feasible, since it is based on the same manufacturing technology as today's computer industry.''Until a few years ago quantum computers were little more than theoretical possibilities, but recent research has shown they could become a realistic proposition. Both Google and Nasa have been developing a quantum computer as part of their artificial intelligence work. However their D-Wave quantum computer needs to be kept at temperatures of around-273°C(-459°F). The latest research by Professor Dzurak and his colleagues, which is published in the journal Nature, has shown it is possible to build them using more conventional materials like silicon. Their work is the first time two qubits have been able to'talk'to each other in a logic gate. On traditional microchips bits are stored typically on a pair of silicon transistors, one of which is switched on while the other is off. In a quantum computer, data is encoded in the'spin, 'or magnetic orientation, of individual electrons. Not only can they be in one of two'up'or'down'spin states, but also a superposition of both up and down. The key step taken by the Australian scientists was to reconfigure traditional transistors so that they can work with qubits instead of bits. Lead author Dr Menno Veldhorst, also from the University of New south wales said:''The silicon chip in your smartphone or tablet already has around one billion transistors on it, with each transistor less than 100 billionths of a metre in size.''We've morphed those silicon transistors into quantum bits by ensuring that each has only one electron associated with it.''We then store the binary code of 0 or 1 on the'spin'of the electron, which is associated with the electron's tiny magnetic field.''The team has taken now out a patent on a full-scale quantum computer chip that could perform functions involving millions of qubits. A practical quantum chip could have a huge impact in areas where classical computers face an uphill struggle. These include weather forecasting, the stock market, drug development, code-breaking and encryption, and exploring the fundamental nature of the universe

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