A group of physicists at UNSW Sydney have built a super-fast version of the central building block of a quantum computer. The research is the milestone result of a vision first outlined by scientists 20 years ago.
A group of scientists led by 2018 Australian of the Year Professor Michelle Simmons have achieved the first two-qubit gate between atom qubits in silicon – a major milestone on the team’s quest to build an atom-scale quantum computer. The pivotal piece of research was published today in world-renowned journal Nature.
A two-qubit gate is the central building block of any quantum computer – and the UNSW team’s version of it is the fastest that’s ever been demonstrated in silicon, completing an operation in 0.8 nanoseconds, which is ~200 times faster than other existing spin-based two-qubit gates.
In the Simmons’ group approach, a two-qubit gate is an operation between two electron spins – comparable to the role that classical logic gates play in conventional electronics. For the first time, the team was able to build a two-qubit gate by placing two atom qubits closer together than ever before, and then – in real-time – controllably observing and measuring their spin states.
The team’s unique approach to quantum computing requires not only the placement of individual atom qubits in silicon but all the associated circuitry to initialise, control and read-out the qubits at the nanoscale – a concept that requires such exquisite precision it was long thought to be impossible. But with this major milestone, the team is now positioned to translate their technology into scalable processors.
Professor Simmons, Director of the Centre of Excellence for Quantum Computation and Communication Technology (CQC2T) and founder of Silicon Quantum Computing Pty Ltd., says the past decade of previous results perfectly set the team up to shift the boundaries of what’s thought to be “humanly possible”.
“Atom qubits hold the world record for the longest coherence times of a qubit in silicon with the highest fidelities,” she says. “Using our unique fabrication technologies, we have already demonstrated the ability to read and initialise single electron spins on atom qubits in silicon with very high accuracy. We’ve also demonstrated that our atomic-scale circuitry has the lowest electrical noise of any system yet devised to connect to a semiconductor qubit.
“Optimising every aspect of the device design with atomic precision has now allowed us to build a really fast, highly accurate two-qubit gate, which is the fundamental building block of a scalable, silicon-based quantum computer.
“We’ve really shown that it is possible to control the world at the atomic scale – and that the benefits of the approach are transformational, including the remarkable speed at which our system operates.”
UNSW Science Dean, Professor Emma Johnston AO, says this key paper further shows just how ground-breaking Professor Simmons’ research is.
“This was one of Michelle’s team’s final milestones to demonstrate that they can actually make a quantum computer using atom qubits. Their next major goal is building a 10-qubit quantum integrated circuit – and we hope they reach that within 3-4 years.”
Getting up and close with qubits – engineering with a precision of just thousand-millionths of a metre
Using a scanning tunnelling microscope to precision-place and encapsulate phosphorus atoms in silicon, the team first had to work out the optimal distance between two qubits to enable the crucial operation.
“Our fabrication technique allows us to place the qubits exactly where we want them. This allows us to engineer our two-qubit gate to be as fast as possible,” says study lead co-author Sam Gorman from CQC2T.
“Not only have we brought the qubits closer together since our last breakthrough, but we have learnt to control every aspect of the device design with sub-nanometer precision to maintain the high fidelities.”
Observing and controlling qubit interactions in real-time
The team was then able to measure how the qubits states evolved in real-time. And, most excitingly, the researchers showed how to control the interaction strength between two electrons on the nano-second timescale.
“Importantly, we were able to bring the qubit’s electrons closer or further apart, effectively turning on and off the interaction between them, a prerequisite for a quantum gate,” says other lead co-author Yu He.
“The tight confinement of the qubit’s electrons, unique to our approach, and the inherently low noise in our system enabled us to demonstrate the fastest two qubit gate in silicon to date.
“The quantum gate we demonstrated, the so-called SWAP gate, is also ideally suited to shuttle quantum information between qubits – and, when combined with a single qubit gate, allows you to run any quantum algorithm.”
A thing of physical impossibility? Not anymore
Professor Simmons says that this is the culmination of two decades’ worth of work.
“This is a massive advance: to be able to control nature at its very smallest level so that we can create interactions between two atoms but also individually talk to each one without disturbing the other is incredible. A lot of people thought this would not be possible,” she says.
“The promise has always been that if we could control the qubit world at this scale, they would be fast, and they sure are!”
The Latest on: Quantum computer
via Google News
The Latest on: Quantum computer
- Fifty perfect photons for 'quantum supremacy'on June 23, 2020 at 6:35 am
Fifty is a critical number for quantum computers capable of solving problems that classic supercomputers cannot solve. Proving quantum supremacy requires at least 50 qubits. For quantum computers ...
- Honeywell claims to have built the highest-performing quantum computer availableon June 22, 2020 at 7:11 am
Multinational conglomerate Honeywell International Inc. is claiming to have built the highest-performing quantum computer available today. It made the announcement in a blogpost on its website. The ...
- Honeywell Unveils The World's Fastest Quantum Computeron June 22, 2020 at 3:20 am
The race toward quantum-computing devices capable of beating digital systems in real-world applications continues.
- To live up to the hype, quantum computers must repair their error problemson June 22, 2020 at 3:04 am
Now, multiply that error rate by the billions or trillions of calculations per second possible in a typical modern computer. For complex computations, a small probability for error can quickly ...
- A love for sci-fi sparked Megan Brown’s STEM path and led to quantum computing at Microsofton June 20, 2020 at 5:00 pm
Megan Brown grew up in a house where an interest in science and science fiction were highly encouraged. She credits weekly viewings of the television series “Stargate SG-1” as one of the reasons ...
- Meet Silq: The first intuitive programming language for quantum computerson June 20, 2020 at 6:17 am
Silq is, its creators claim, the world’s first high-level quantum computer programming language. Here's why it's so exciting for those working in the field.
- Honeywell Says It Has Built The World’s Most Powerful Quantum Computeron June 19, 2020 at 9:26 am
In the race to the future of quantum computing, Honeywell has just secured a fresh lead. The North Carolina-based conglomerate announced Thursday that it has produced the world’s fastest quantum ...
- Honeywell claims to surpass IBM with the world's fastest quantum computeron June 19, 2020 at 8:22 am
Honeywell declared on Thursday that it has the world's highest-performing. Touting a quantum volume of 64—the metric used to convey the effectiveness of a quant ...
- This Is the First Universal Language for Quantum Computerson June 19, 2020 at 5:25 am
A quantum computing startup called Quantum Machines has released a new programming language called QUA. The language runs on the startup’s proprietary Quantum Orchestration Platform. Quantum Machines ...
- Honeywell will let other companies tap into its quantum computeron June 18, 2020 at 3:22 pm
Typically, when most companies talk about quantum computers, they usually mention qubits. Honeywell is instead using a metric called quantum volume to play up the capabilities of its machine. The term ...
via Bing News