Centre Updates

CQC2T physicist Dr Rose Ahlefeldt named ACT Scientist of the Year

Congratulation to CQC2T researcher Dr Rose Ahlefeldt from the Australian National University (ANU) who was named ACT Scientist of the Year.

Dr Ahlefeldt's research is trying to find the right materials to build the quantum memories needed for quantum computers. These computers could solve some of the world's "impossible" problems.

"I am trying to understand how the atoms in the crystals interact with the light, so I can choose the right materials to make better quantum memories." says Dr Ahlefeldt.

"One day we're going to build quantum computers that can solve problems that are impossible for our current computers. Researchers have already identified many uses for these computers, including enhancing artificial intelligence establishing secure communications and eventually building a quantum internet."

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Hundreds of school students get exclusive insights into the world of quantum

200 primary and secondary school students got a rare peek into what life as a scientist could be like, as Professor Michelle Simmons opened the doors of the Centre for Quantum Computation and Communication Technology (CQC2T) ahead of National Science Week.

When Scientia Professor Michelle Simmons became Australian of the Year 2018, her acceptance speech touched on themes that resonated with many school students and teachers: her encouragement of all young people to pursue what they love, to set their sights high, to tackle the hardest challenges in life and to be the creators – not just the users – of technology. Following the ceremony – and numerous subsequent speech invites from schools across Australia – Professor Simmons and her team decided to open the doors of the Centre for Quantum Computation and Communication Technology for one full day, to offer students the opportunity to see the team’s ground-breaking research in action – a first in the centre’s history.

Professor Simmons said the goal of the day was to open the students’ minds to the possibilities that a career in STEM offers. “When I was younger, I got to see a fabrication plant in the US, and observed how they make semi-conductor chips. It completely opened my mind to the world of possibility that was out there. I remember thinking that all children should see this. “So here we are in Australia, we've got this great facility of building chips in-house, so I'm hoping we opened the students’ eyes to what's out there, to all the kind of jobs they can have, and just get them excited by science.”

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
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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

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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.”


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.”



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
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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