A team of Australian and Canadian researchers have published a new study they say demonstrates a path towards scaling individual quantum bits (qubits) to a mini-quantum computer by using holes.
The Australian Research Council (ARC) Centre of Excellence in Future Low-Energy Electronics Technologies (FLEET) said the work indicates holes are the solution to operational speed/coherence trade-off.
"One way to make a quantum bit is to use the 'spin' of an electron, which can point either up or down. To make quantum computers as fast and power-efficient as possible we would like to operate them using only electric fields, which are applied using ordinary electrodes," FLEET said, alongside researchers from the ARC Centre of Excellence for Quantum Computation and Communication Technology (CQC2T) hosted by the University of New South Wales (UNSW), and participants from the University of British Columbia.
"Although spin does not ordinarily 'talk' to electric fields, in some materials spins can interact with electric fields indirectly, and these are some of the hottest materials currently studied in quantum computing."
The group explained the interaction that enables spins to talk to electric fields -- the spin-orbit interaction -- is traced back to Einstein's theory of relativity. They said the fear of quantum-computing researchers has been that when this interaction is strong, any gain in operation speed would be offset by a loss in coherence.
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"Essentially, how long we can preserve quantum information," FLEET said.
"If electrons start to talk to the electric fields we apply in the lab, this means they are also exposed to unwanted, fluctuating electric fields that exist in any material (generically called `noise') and those electrons' fragile quantum information would be destroyed," Associate Professor Dimi Culcer, who led the theoretical roadmap study, added.
"But our study has shown this fear is not justified."
Culcer said the team's theoretical studies show that a solution is reached by using holes, which can be thought of as the absence of an electron, behaving like positively-charged electrons.
"In this way, a quantum bit can be made robust against charge fluctuations stemming from the solid background," FLEET said.
"Moreover, the 'sweet spot' at which the qubit is least sensitive to such noise is also the point at which it can be operated the fastest."
"Our study predicts such a point exists in every quantum bit made of holes and provides a set of guidelines for experimentalists to reach these points in their labs," Culcer added.
Over in Japan, RIKEN and Fujitsu have jointly opened a new centre to promote joint research and development of foundational technologies to put superconducting quantum computers into practical use.
The RIKEN RQC-Fujitsu Collaboration Center will see the development of hardware and software technologies to realise a quantum computer with as many as 1,000 qubits and develop applications using a prototype quantum computer.
These efforts will be centred around RIKEN's ongoing work with advanced superconducting quantum computing technologies along with Fujitsu's computing technologies, the pair said.