Australian scientists from the University of NSW have claimed a world record for preserving a single quantum bit held in solid state.
A quantum bit or ‘qubit’ is the basic unit of data for quantum computers. The longer the information can be preserved in a nucleus of a phosphorus atom, the more complex and extensive calculations can be performed.
The UNSW scientists were able to preserve the information for 35 seconds. “Half a minute is an eternity in the quantum world,” said associate professor Andrea Morello from UNSW’s School of Electrical Engineering and Telecommunications.
The scientists also created two different pathways to building quantum computers in silicon. The first is a natural phosphorus atom qubit, which contains the electron and nuclear spin. It provides 99.99 per cent accuracy or the chance of one error to occur in every 10,000 quantum operations.
The other is an artificial atom qubit, which is made from similar transistors to the metal-oxide semiconductor field-effect transistor (MOSFET) or silicon transistors used in smartphones or laptops. It provides an accuracy of over 99 per cent.
“Even though methods to correct errors do exist, their effectiveness is only guaranteed if the errors occur less than 1 per cent of the time. Our experiments are among the first in solid-state, and the first-ever in silicon, to fulfil this requirement,” said scientia professor Andrew Dzurak, director of the Australian National Fabrication Facility at UNSW.
Both types of qubits can be highly accurate when put inside a thin layer of silicon-28 non-magnetic isotope (pure Silicon) that does not disturb the qubit with magnetic noise, unlike naturally occurring Silicon.
Both the natural and the artificial qubits can be combined in a quantum computer in future to “exploit the best of both methods”, Morello said.
“Preserving a ‘quantum superposition’ for such a long time, and inside what is basically a modified version of a normal transistor, is something that almost nobody believed possible until today,” he added.