Australian scientists make two atom qubits “talk” to each other

The unique Australian approach involving creation of quantum bits from precisely positioned individual atoms in silicon has shown much promise, as UNSW Sydney-led scientists showed for the first time that they could make two of these atom qubits ''talk'' to each other.

The team – led by UNSW Scientia professor Michelle Simmons, director of the centre of excellence for Quantum Computation and Communication Technology, or CQC2T – is the only group in the world that has the ability to see the exact position of their qubits in the solid state.

Simmons' team created the atom qubits by precisely positioning and encapsulating individual phosphorus atoms within a silicon chip. Information is stored on the quantum spin of a single phosphorus electron.

The latest advance of the team comes as the first observation of controllable interactions between two of these qubits. It is published in the journal Nature Communications and comes after two other recent breakthroughs using this unique approach to building a quantum computer.

With the optimisation of their nano-manufacturing process, Simmons' team has also recently created quantum circuitry having the lowest recorded electrical noise of any semiconductor device.

They have also created an electron spin qubit with the longest lifetime ever reported in a nano-electric device – 30 seconds.

''The combined results from these three research papers confirm the extremely promising prospects for building multi-qubit systems using our atom qubits,'' says Simmons.

Meanwhile, Google took lead this week in the race toward ''quantum supremacy,'' with the introduction of a new 72-qubit quantum processor called Bristlecone. According to experts, the gate-based superconducting system will be instrumental in Google's efforts to demonstrate the first quantum technology to show advantage over today's leading classical machines.

Bristlecone (so nicknamed due to the arrangement of qubits in a pinecone pattern) will be employed as a testbed for researching system error rates and boosting scalability of Google's qubit technology.

It will also help in exploring near-term applications in quantum simulation, optimisation, and machine learning.