Centre Updates

Tuning into quantum: scientists unlock signal frequency control of precision atom qubits

CQC2T scientists, led by Prof Michelle Simmons, have achieved a new milestone in their approach to creating a quantum computer chip in silicon, demonstrating the ability to tune the control frequency of a qubit by engineering its atomic configuration.

The team from UNSW Sydney successfully implemented an atomic engineering strategy for individually addressing closely spaced spin qubits in silicon. The scientists created engineered phosphorus molecules with different separations between the atoms within the molecule allowing for families of qubits with different control frequencies. Each molecule could then be operated individually by selecting the frequency that controlled its electron spin.

“The ability to engineer the number of atoms within the qubits provides a way of selectively addressing one qubit from another, resulting in lower error rates even though they are so closely spaced,” says Professor Simmons. “These results highlight the ongoing advantages of atomic qubits in silicon.”

Tuning in and individually controlling qubits within a 2 qubit system is a precursor to demonstrating the entangled states that are necessary for a quantum computer to function and carry out complex calculations.

“We can tune into this or that molecule – a bit like tuning in to different radio stations,” says Sam Hile, lead co-author of the paper and Research Fellow at UNSW. “It creates a built-in address which will provide significant benefits for building a silicon quantum computer.”

Read paper here
Read article here

Centre researchers set world record simulating quantum power

CQC2T scientists from the University of Melbourne have set a world record in simulating quantum power on a classical computer, a key step in becoming 'quantum-ready' ahead of when actual quantum computers are scaled up in size. Deputy Director of CQC2T, Professor Lloyd Hollenberg and team members Dr Charles Hill and lead author Masters student Aidan Dang, simulated the output of a 60-qubit quantum computer, which in general would require up to 18,000 petabytes, or more than a billion laptops, to describe – capabilities well beyond the largest supercomputer.


A representation of quantum computing in action showing the “forest” of differing probabilities that the machine uses to more efficiently guide it towards the answer to a problem. The above example is a simulation of a quantum computer finding the prime factors of a number using Shor’s Algorithm.
Picture: Matthew Davis, Gregory White and Aidan Dang

Read more detail here

CQC2T Deputy Director Lloyd Hollenberg elected a Fellow of the Australian Academy


CQC2T Deputy Director Professor Lloyd Hollenberg

Professor Lloyd Hollenberg, who is Deputy Director of CQC2T, the Thomas Baker Chair at the University of Melbourne, and an Australian Research Council Laureate Fellow, has been elected today as a Fellow of the Australian Academy of Science.

Lloyd has created the physical-quantum information basis for a full-scale silicon quantum computer, drawing on his deep understanding of the physics involved. He has achieved major theoretical and experimental advances in the use of nitrogen-vacancy centres in diamond as quantum sensors in physical and biological applications. The Director, Chief Investigators, research staff and students congratulate Lloyd on his achievements.

More information here

CQC2T Director Professor Michelle Simmons elected Fellow of the Royal Society


CQC2T Director Professor Michelle Simmons

The Royal Society of London, the world’s oldest independent scientific academy, announced Professor Michelle Simmons has been elected to receive a Fellowship of the Royal Society.

The fellowship, which is the highest scientific honour bestowed by the academy, is a lifetime membership. Fellowships are awarded to individuals who have been judged to have made a “substantial contribution to the improvement of natural knowledge, including mathematics, engineering science and medical science.”

More information here

CQC2T researchers (Griffith Uni) report Big Bell Test work in Nature

CQC2T researchers at Griffith University have played an important role in a major international collaboration that tested quantum nonlocality – Einsten’s “spooky action at a distance” – in a suite of experiments worldwide. Nonlocal effects such as entanglement underlie the quantum computation and communication technologies being pursued in CQC2T. The joint work of the “Big Bell Test” (BBT) consortium, published in Nature today (https://www.nature.com/articles/s41586-018-0085-3) , used random numbers sourced from people’s free will to rigorously ensure unpredictability in the measurement settings required for such tests. The project used an online game through which members of the public provided random numbers to the experiments in real time. Thus, the project is a flagship for new approaches to citizen involvement in science, and for science outreach.

The Griffith University team, led by Dr Raj Patel and Professor Geoff Pryde, performed a test of "quantum steering” as part of the BBT. Steering is a practical form of quantum non-locality testing that is resistant to real-world device imperfections, and has direct application to quantum communication tasks such as verifying that entanglement has been shared between remote parties. Pryde said, “One of the things that was exciting and really interesting for us was to be part of a big project that required a large amount of coordination. From compiling random numbers from the public to disseminating them between the experiments, and receiving and using them in a timely way, the level of collaboration was remarkable. I also particularly enjoyed the outreach and public involvement side; I enjoyed that we gave people an opportunity to do something which influenced how the experiment ran.”

https://www.sciencedaily.com/releases/2018/05/180509135409.htm

CQC2T CI Prof Michael Bremner (UTS) co-authors Nature Physics paper on quantum supremacy


CQC2T CI Prof Michael Bremner (UTS)

CQC2T CI Prof Michael Bremner (UTS) links with Google, NASA, UCSB on Nature Physics paper to try to define when quantum computers will overtake classical computers. The researchers said that quantum computers would need almost 50 qubits to process information exponentially faster than a classical supercomputer.

UTS said the first research marks the first clear attempt to identify a benchmark at which quantum computing will surpass the capability of classical computers - which is known as quantum supremacy.
Chief investigator of the UTS branch of the ARC Centre for Quantum Computation and Communication Technology, Professor Michael Bremner, said the line was difficult to define because the advantages offered by quantum computers can be subtle.

“Some applications can have an exponential quantum speed-up over classical computers, while others receive no benefit at all,” he said.
“Understanding when quantum computers become useful is essential, especially when we are limited to using the noisy intermediate-scale devices that currently exist.

“We attempted to find the frontier between classical and quantum computing. We wanted to find the smallest quantum circuits that can do something that cannot be done at all on a classical computer.”

https://www.nature.com/articles/s41567-018-0124-x

https://www.itnews.com.au/news/uts-researchers-join-quantum-benchmark-pr...

Feynman inspires new CQC2T Nature Communications paper

UNSW physics researcher Sam Gorman

Director of CQC2T, Scientia Professor Michelle Simmons said her team’s approach to building a quantum computer “from the ground up, atom by atom” is inspired by physicist Richard Feynman who said: ‘what I cannot create, I do not understand’. Centre researchers create their 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. Simmons’ team use a scanning probe to directly measure the atom’s wave function to show the exact physical location in the chip. “We are the only group in the world who can actually see where our qubits are,” said Prof Simmons.

In the new paper, the team show they can control the interactions between two of these atom qubits so the quantum spins of their electrons become correlated. Building on two other recent results, these three papers collectively confirm the extremely promising prospects for building multi-qubit systems using Centre atom qubits.

Read paper here
Read article here
Watch video

CQC2T demonstrates Bell inequality with Light Wave

Centre research associate Oliver Thearle in the ANU Quantum Optics lab

A new CQC2T paper in Physical Review Letters has demonstrated the first observation of Bell correlations in a continuous variable system, thereby showing the strength of photon number correlations when inferred through homodyne measurements.

Lead author from ANU Oliver Thearle said the paper’s significance is in the fact that “it is the first demonstration of a Violation of Bell’s inequality using light fields as opposed to photon counting as was originally proposed by Bell. This is possible through the wave particle duality of light”.

Violation of Bell inequality is a fundamental test to rule out local hidden variable model descriptions of correlations between two physically separated systems. There have been a number of experiments in which a Bell inequality has been violated using discrete-variable systems in recent years. The ANU-led Centre team demonstrated a violation of Bell’s inequality using continuous variable quadrature measurements. This means that the wave nature of light also leads to the same conclusion that local hidden variable is an insufficient description of reality.

By creating a four-mode entangled state with homodyne detection, they recorded a clear violation with a Bell value of B = 2.31±0.02, where B ≤ 2 validates local hidden variables. This opens new possibilities for using continuous variable systems for a number of quantum communication applications, such as a source independent quantum random number generator.

Centre Chief Investigator Prof Ping Koy Lam from the ANU said, “Our experiment using bright laser beams complements very well with the recent successful loophole free Bell test demonstrations in the discrete variable regime.”

Four CQC2T Chief Investigators from the ANU and the University of Queensland collaborated on this paper.

Full paper is here

Westpac Future Leaders Scholarship awarded to CQC2T post-graduate student

CQC2T is proud to announce that one of our new 2018 PhD students has been awarded a Westpac Future Leaders Scholarship to undertake post-graduate study.

Joseph Rowlands graduated with First Class Honours for his experimental research in aeroacoustics, and is now focusing on quantum computing. His PhD will be under the supervision of UNSW scientist Professor Michelle Simmons, Director of the Centre of Excellence for Quantum Computation and Communication Technology, and 2018 Australian of the Year.

'Quantum computing will change the digital world by providing an exponential increase in computational power over traditional machines. This will create new industries, allow currently impossible research to be carried out, leading to new technologies not yet even imagined,' he says.

'Australia is leading this 'space race of the computing era'. For both economic and strategic reasons, it is imperative that Australia stay at the forefront of this exciting technological development.'

CQC2T Director Professor Michelle Simmons is Australian of the Year 2018

On behalf of all researchers and partners of CQC2T, we congratulate Scientia Professor Michelle Simmons, who was tonight named 2018 Australian of the Year in recognition of her pioneering research and inspiring leadership in quantum computing.

Professor Simmons, who is a UNSW Professor of Physics and Director of the Australian Research Council Centre of Excellence for Quantum Computation and Communication Technology based at UNSW, was awarded the honour by the Australian Prime Minister, Malcolm Turnbull, at a ceremony at Parliament House in Canberra.

Chair of the Centre Advisory Committee, Peter Yates AM said “Michelle’s achievements and those of her team are hugely exciting for the recognition of science in Australia. Her leadership of the Centre and her field is an inspiration to us all’.

As Centre Director she leads a team of more than 200 researchers at eight Australian universities who are developing a suite of technologies for quantum computing, information storage and communications.

For further information click here