The research was conducted within the Simmons group at the Centre of Excellence for Quantum Computation and Communication Technology. The team was led by Professor Michelle Simmons, Australian of the Year, and their findings were published on Tuesday in the Physical Review X journal with PhD student Prasanna Pakkiam as lead author.
Quantum bits — known as qubits — made from electrons hosted on single atoms in semiconductors are a promising platform for large-scale quantum computers due to their long-lasting stability. Creating qubits by precisely positioning and encapsulating individual phosphorus atoms within a silicon chip is a uniquely Australian approach, which Simmons’ team has been leading globally. Prior to the work of Simmons’ team, all the connections and gates required for scaling the phosphorus atom architecture was a challenge.
“To monitor even one qubit, you have to build multiple connections and gates around individual atoms, where there is not a lot of room,” says Professor Simmons. “What’s more, you need high-quality qubits in close proximity so they can talk to each other – which is only achievable if you’ve got as little gate infrastructure around them as possible.”
By integrating the read-out sensor into one of the control gates, the UNSW team could drop this to just two gates; one each for control and reading.
“Not only is our system more compact, but by integrating a superconducting circuit attached to the gate we now have the sensitivity to determine the quantum state of the qubit by measuring whether an electron moves between two neighbouring atoms,” Pakkiam said. “And we’ve shown that we can do this real-time with just one measurement — single shot — without the need to repeat the experiment and average the outcomes.
“This represents a major advance in how we read information embedded in our qubits,” Simmons said. “The result confirms that single-gate reading of qubits is now reaching the sensitivity needed to perform the necessary quantum error correction for a scalable quantum computer.”
Australia’s first quantum computing company, Silicon Quantum Computing, has been working to create and commercialise a quantum computer based on intellectual property developed at the Australian Centre of Excellence for Quantum Computation and Communication Technology.
SQC believes quantum computing will ultimately have a significant impact across the global economy, with possible applications in software design, machine learning, scheduling and logistical planning, financial analysis, stock market modelling, software and hardware verification, climate modelling, rapid drug design and testing, and early disease detection and prevention.