Scientists successfully encoded quantum information in silicon using electrical pulses, potentially opening the door for the development of affordable quantum computers.
The new control method for future quantum computers is considered to be a major breakthrough in the field, the University of New South Wales reported. Today's computers store their information on transistors and hard drives, but quantum computers encode data in the quantum states of microscopic objects, called qubits.
In the past the researchers had already demonstrated single-atom spin qubits in silicon, and improved the control of qubits to an accuracy of over 99 percent, but this new study adds a piece that has been missing from the puzzle.
"We demonstrated that a highly coherent qubit, like the spin of a single phosphorus atom in isotopically enriched silicon, can be controlled using electric fields, instead of using pulses of oscillating magnetic fields," said UNSW's Arne Laucht, post-doctoral researcher and lead author of the study.
The new method works by distorting the shape of the electron cloud attached to an atom using a localized electron field.
"This distortion at the atomic level has the effect of modifying the frequency at which the electron responds," said Associate Professor Andrea Morello. "Therefore, we can selectively choose which qubit to operate. It's a bit like selecting which radio station we tune to, by turning a simple knob. Here, the 'knob' is the voltage applied to a small electrode placed above the atom."
The findings suggest scientists could locally control the individual qubits with electrical fields in a large-scale quantum computer using nothing more than inexpensive voltage generators, instead of pricey high-frequency microwave sources. This type of quantum bit can be manufactured using a similar technology to what is used in conventional computers on the market today. The key to this method's success is the placement of qubits inside a layer of purified silicon that contains exclusively the silicon-28 isotope.
"This isotope is perfectly non-magnetic and, unlike those in naturally occurring silicon, does not disturb the quantum bit," Associate Professor Morello said.
The findings were published in a recent edition of the journal Science Advances.
