Quantum computing on a large scale: Australian scientists achieve a compact, sensitive qubit readout

The team of Professor Michelle Simmons of UNSW Sydney has demonstrated a compact sensor for accessing information stored in the electrons of individual atoms – a breakthrough that brings us a step closer to scalable quantum computing in silicon.

The research, conducted within the Simmons group in the Center of Excellence for Quantum Computation and Communication Technology (CQC2T) with PhD student Prasanna Pakkiam as lead author, was published today in the prestigious journal Physical assessment X (PRX).

Quantum bits (or qubits) made from electrons hosted on single atoms in semiconductors is a promising platform for large-scale quantum computers, thanks to their long-term stability. Creating qubits by accurately positioning and encapsulating individual phosphor atoms within a silicon chip is a unique Australian approach that has led the Simmons team worldwide.

But adding all the connections and gates needed for scaling up the phosphorus atom architecture would be a challenge – until now.

"To monitor even one qubit, you need multiple connections and gates to build individual atoms, where there is not much room," says Professor Simmons. "Moreover, you need high quality qubits in the immediate vicinity so that they can talk to each other – which is only feasible if you have as little port infrastructure around them as possible."

Compared with other approaches for making a quantum computer, Simmons & # 39; s system already had a relatively low port density. But conventional measurements still required at least 4 ports per qubit: 1 to control it and 3 to read it.

By integrating the readout sensor into one of the operating ports, the UNSW team has been able to transfer this to only two ports: 1 for control and 1 for reading.

"Not only is our system more compact, but by integrating a superconducting circuit at the gate, we now have the sensitivity to determine the quantum state of the qubit by measuring whether an electron moves between two adjacent atoms", says lead author Pakkiam.

"And we've shown that we can do this in real time with just one measurement – single shot – without the need to repeat the experiment and calculate the outcomes."

"This represents a major advance in the way we read information embedded in our qubits," Simmons concludes. "The result confirms that reading qubits with one port now reaches the sensitivity needed to perform the necessary quantum error correction for a scalable quantum computer."

The first quantum computer company in Australia

Since May 2017, Australia's first quantum computer company, Silicon Quantum Computing Pty Limited (SQC), has been creating and commercializing a quantum computer based on a suite of intellectual property developed at the Australian Center of Excellence for Quantum Computation and Communication Technology (CQC2T). ).

Based in part at CQC2T on the UNSW Campus in Sydney, SQC invests in a portfolio of parallel technology development projects led by world-leading quantum researchers, including Australian of the Year and Laureate Professor Michelle Simmons. The goal is to produce a 10-qubit demonstration device in silicon by 2022 as the precursor of a commercially-based silicon-based quantum computer.

SQC believes that quantum computing will ultimately have a significant impact in the global economy, with potential applications in software design, machine learning, planning and logistics planning, financial analysis, stock market modeling, software and hardware verification, climate modeling, rapid drug design and testing and early disease detection. and prevention.

Created through a unique coalition of governments, companies and universities, SQC competes with some of the largest tech multinationals and foreign research laboratories.

In addition to developing its own technology and intellectual property, SQC will continue to work with CQC2T and other participants in the Australian and international Quantum Computing ecosystems, to build and develop a silicon quantum computing industry in Australia and ultimately to develop its products. and services to global markets.

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