Tropes

phys_org 00176.txt

#Physicists set new records for silicon quantum computing Two research teams working in the same laboratories at UNSW Australia have found distinct solutions to a critical challenge that has held back the realisation of super powerful quantum computers. The teams created two types of quantum bits or qubits the building blocks for quantum computers that each process quantum data with an accuracy above 99%.%The two findings have been published simultaneously today in the journal Nature Nanotechnology. For quantum computing to become a reality we need to operate the bits with very low error rates says Scientia Professor Andrew Dzurak who is Director of the Australian National Fabrication Facility at UNSW where the devices were made. We've now come up with two parallel pathways for building a quantum computer in silicon each of which shows this super accuracy adds Associate professor Andrea Morello from UNSW's School of Electrical engineering and Telecommunications. The UNSW teams which are affiliated also with the ARC Centre of Excellence for Quantum Computation & Communication Technology were first in the world to demonstrate single-atom spin qubits in silicon reported in Nature in 2012 and 2013. Now the team led by Dzurak has discovered a way to create an artificial atom qubit with a device remarkably similar to the silicon transistors used in consumer electronics known as MOSFETS. Postdoctoral researcher Menno Veldhorst lead author on the paper reporting the artificial atom qubit says It is really amazing that we can make such an accurate qubit using pretty much the same devices as we have in our laptops and phones. Meanwhile Morello's team has been pushing the natural phosphorus atom qubit to the extremes of performance. Dr Juha Muhonen a postdoctoral researcher and lead author on the natural atom qubit paper notes: The phosphorus atom contains in fact two qubits: the electron and the nucleus. With the nucleus in particular we have achieved accuracy close to 99.99%.%That means only one error for every 10000 quantum operations. Dzurak explains that even though methods to correct errors do exist their effectiveness is guaranteed only if the errors occur less than 1%of the time. Our experiments are among the first in solid-state and the first-ever in silicon to fulfill this requirement. The high-accuracy operations for both natural and artificial atom qubits is achieved by placing each inside a thin layer of specially purified silicon containing only the silicon-28 isotope. This isotope is perfectly nonmagnetic and unlike those in naturally occurring silicon does not disturb the quantum bit. The purified silicon was provided through collaboration with Professor Kohei Itoh from Keio University in Japan. The next step for the researchers is to build pairs of highly accurate quantum bits. Large quantum computers are expected to consist of many thousands or millions of qubits and may integrate both natural and artificial atoms. Morello's research team also established a world-record coherence time for a single quantum bit held in solid state. Coherence time is a measure of how long you can preserve quantum information before it's lost Morello says. The longer the coherence time the easier it becomes to perform long sequences of operations and therefore more complex calculations. The team was able to store quantum information in a phosphorus nucleus for more than 30 seconds. Half a minute is an eternity in the quantum world. Preserving a'quantum superposition'for such a long time and inside what is modified basically a version of a normal transistor is something that almost nobody believed possible until today Morello says. For our two groups to simultaneously obtain these dramatic results with two quite different systems is very special in particular because we are really great mates adds Dzurak. Explore further: Pairing up single atoms in silicon for quantum computing More information: Storing quantum information for 30 seconds in a nanoelectronic device Nature Nanotechnology DOI: 10.1038/nnano. 2014.211 An addressable quantum dot qubit with fault-tolerant control-fidelity Nature Nanotechnology DOI: 10.1038/nnano. 2014.21 1

< Back - Next >