Discovery of previously unknown effect makes compact, ultra-fast control of spin qubits possible.
UNSW Sydney engineers have discovered a new way of precisely controlling single electrons nestled in quantum dots that run logic gates. The new mechanism is also less bulky and requires fewer parts, which could prove essential to making large-scale silicon quantum computers a reality.
The serendipitous discovery, made by engineers at the quantum computing start-up Diraq and UNSW, is detailed in the journal Nature Nanotechnology.
“This was a completely new effect we’d never seen before, which we didn’t quite understand at first,” said lead author Dr Will Gilbert, a quantum processor engineer at Diraq, a UNSW spin-off company based at its Kensington campus. “But it quickly became clear that this was a powerful new way of controlling spins in a quantum dot. And that was super exciting.”
Logic gates are the basic building block of all computation. They allow ‘bits’ – or binary digits (0s and 1s) – to work together to process information. However, a quantum bit (or qubit) exists in both of these states at once – a condition known as a ‘superposition’. This allows a multitude of computation strategies – some exponentially faster, some operating simultaneously – that are beyond classical computers. Qubits themselves are made up of ‘quantum dots’ – tiny nanodevices which can trap one or a few electrons. Precise control of the electrons is necessary for computation to occur.
Using electric rather than magnetic fields
While experimenting with different geometrical combinations of devices just billionths of a metre in size that control quantum dots, along with various types of miniscule magnets and antennas that drive their operations, Dr Tuomo Tanttu from UNSW Engineering stumbled across a strange effect.
“I was trying to really accurately operate a two-qubit gate, iterating through a lot of different devices, slightly different geometries, different materials stacks and different control techniques,” said Dr Tanttu, who is also a measurement engineer at Diraq. “Then this strange peak popped up. It looked like the rate of rotation for one of the qubits was speeding up, which I’d never seen in four years of running these experiments.”
Read more: For the longest time: quantum computing engineers set new standard in silicon chip performance
What he had discovered, the engineers later realised, was a new way of manipulating the quantum state of a single qubit by using electric fields, rather than the magnetic fields they had been using previously. Since the discovery was made in 2020, the engineers have been perfecting the technique – which has become another tool in their arsenal to fulfil Diraq’s ambition of building billions of qubits on a single chip.
“This is a new way to manipulate qubits, and it’s less bulky to build – you don’t need to fabricate cobalt micro-magnets or an antenna right next to the qubits to generate the control effect,” said Dr Gilbert. “It removes the requirement of placing extra structures around each gate. So, there’s less clutter.”
Controlling single electrons without disturbing others nearby is essential for quantum information processing in silicon. There are two established methods: electron spin resonance (ESR) using an on-chip microwave antenna, and electric dipole spin resonance (EDSR), which relies on an induced gradient magnetic field. The newly discovered technique is known as ‘intrinsic spin-orbit EDSR’.
“Normally, we design our microwave antennas to deliver purely magnetic fields,” said Dr Tanttu. “But this particular antenna design generated more of an electric field than we wanted – but that turned out to be lucky, because we discovered a new effect we can use to manipulate qubits. That’s serendipity for you.”
Building on making quantum computing in silicon a reality
“This is a gem of a new mechanism, which just adds to the trove of proprietary technology we’ve developed over the past 20 years of research,” said Professor Andrew Dzurak, Scientia Professor in Quantum Engineering at UNSW and CEO and founder of Diraq. Professor Dzurak led the team that built the first quantum logic gate in silicon in 2015.
“It builds on our work to make quantum computing in silicon a reality, based on essentially the same semiconductor component technology as existing computer chips, rather than relying on exotic materials.
“Since it’s based on the same CMOS technology as today’s computer industry, our approach will make it easier and faster to scale up for commercial production and achieve our goal of fabricating billions of qubits on a single chip.”
CMOS (or complementary metal-oxide-semiconductor, pronounced “see-moss”) is the fabrication process at the heart of modern computers. It’s used for making all sorts of integrated circuit components – including microprocessors, microcontrollers, memory chips and other digital logic circuits, as well as analogue circuits such as image sensors and data converters.
Building a quantum computer has been called the ‘space race of the 21st century’ – a difficult and ambitious challenge with the potential to deliver revolutionary tools for tackling otherwise impossible calculations, such as the design of complex drugs and advanced materials, or the rapid search of massive, unsorted databases.
“We often think of landing on the Moon as humanity’s greatest technological marvel,” said Professor Dzurak. “But the truth is, today’s CMOS chips – with billions of operating devices integrated together to work like a symphony, and that you carry in your pocket – that’s an astounding technical achievement and one that’s revolutionised modern life. Quantum computing will be equally astonishing.”
Original Article: New spin control method brings billion-qubit quantum chips closer
More from: University of New South Wales
The Latest Updates from Bing News
Go deeper with Bing News on:
Billion-qubit quantum chips
- U.S. Seeks to Prevent China From Benefiting From $52 Billion Chips Funding
U.S. Seeks to Prevent China From Benefiting From $52 Billion Chips ... This measure covers chips "including current-generation and mature-node chips used for quantum computing, in radiation ...
- Everything You Wanted to Know about Quantum Computing
That number is forecast to skyrocket to $15 billion US by 2028 ... Here is an example of a multi-qubit chip for computing things, such as quantum simulations of advanced materials, that was created at ...
- Quantum computer startup SEEQC unveils digital chip that operates at super cold temp
The first chip it unveiled Wednesday sits directly under the quantum processor and controls the qubits, and reads out ... provider reaching more than one billion people every day.
- Quantum market to be worth $2bn in 2030
The quantum market will be worth $2.1 billion in 2030 ... three different technological qubit techniques: superconducting, trapped ions, and spin. The trend today is to have a “full stack approach” ...
- Anhui tech startup eyes quantum computing revolution
These futuristic chips contain quantum bits, or "qubits" — quantum's key advantage ... have a conservative estimated value of up to $700 billion by 2035 for industries such as pharmaceuticals ...
Go deeper with Bing News on:
Intrinsic spin-orbit EDSR
- Spin 1.0 aims to simplify WebAssembly microservices
Fermyon Technologies has published Spin 1.0, the first stable release of the company’s open source framework for building event-driven microservice applications with WebAssembly. Spin 1.0 was ...
- Every ‘RuPaul’s Drag Race’ Spin-Off Set to Air in 2023
One of two non-US Drag Race series that RuPaul himself hosts, RuPaul’s Drag Race Down Under searches across Australia and New Zealand for their best drag performers. Its third season is due out ...
- ORIGINAL SPIN: The Prince Graphite
Maybe it was the rock-solid feel from the cross-bar stabilizer in the throat, the hefty spin production from the open string pattern or the iconic stealthy green-and-black cosmetics—yeah ...
- World's first 3D-printed rocket launches successfully, but fails to reach orbit: Watch liftoff
In a third attempt, the world’s first 3D-printed rocket made it off the launch pad Wednesday night but failed to reach orbit and eventually crashed into the Atlantic Ocean in a key test ...
- Virgin Orbit raising $200 million from investor Matthew Brown, closing deal as soon as Thursday
Virgin Orbit is in final talks to raise funds from Texas-based investor Matthew Brown, amounting to an injection of $200 million. Virgin Orbit and Brown began deal talks last week, around the same ...