The discovery of a previously unknown effect enables compact and ultrafast control of spin qubits.
Engineers at UNSW Sydney have discovered a new way to precisely control single electrons surrounded by quantum dots that run logic gates.The new mechanism is also less bulky and requires fewer parts. This could prove essential for realizing large-scale silicon quantum computers.
This serendipitous discovery, made by engineers at quantum computing startup Diraq and UNSW, is detailed in the journal Nature Nanotechnology.
“It’s a completely new effect that we’ve never seen before, and it didn’t really make sense to us at first,” says lead author and quantum processor engineer at Diraq, a UNSW spin-off company based on Kensington campus. said Will Gilbert, Ph.D. “But it quickly became apparent that this was a powerful new way to control the spin of quantum dots. And it was very exciting.”
Logic gates are the basic building blocks of all computations. This allows the “bits” or binary numbers (0’s and 1’s) to work together to process information. However, a qubit (or qubit) exists in both these states simultaneously. This is a condition known as “superposition”. This enables a multitude of computational strategies beyond classical computers, some exponentially fast, others working simultaneously. The qubits themselves are made up of “quantum dots”. This is a small nanodevice that can trap one or a few electrons. Electrons must be precisely controlled to perform calculations.
use an electric field instead of a magnetic field
Dr. Tuomo Tanttu of UNSW Engineering experiments with billionths of a meter sized devices to control quantum dots and different geometric combinations of different types of tiny magnets and antennas to drive their operation. While doing so, I came across a strange effect.
Dr. Tanttu, who is also a measurement engineer at Diraq, said: “Then this weird peak appeared. One of his qubits seemed to be spinning faster, which is what he’s seen in the four years he’s been running these experiments. I never had a problem.”
Read more: For a long time: Quantum Computing Engineers Set New Bar for Silicon Chip Performance
What he discovered, as engineers later realized, was a new way to manipulate the quantum states of single qubits using electric fields rather than the magnetic fields they had previously used. Since its discovery in 2020, engineers have perfected the technology. This became one of his weapons in realizing his Diraq ambition to build billions of qubits on a single chip.
“It’s a new way of manipulating qubits, and it’s not bulky to build. We don’t need to fabricate cobalt micromagnets or antennas right next to the qubits to produce control effects,” Dr. Gilbert said. said. “You don’t have to put extra structures around each gate, so there’s less confusion.”
Controlling single electrons without interfering with other nearby electrons is essential for quantum information processing in silicon. There are two well-established methods of his: electron spin resonance (ESR), which uses an on-chip microwave antenna, and electric dipole spin resonance (EDSR), which relies on an induced gradient magnetic field. The newly discovered technology is known as ‘eigenspin-orbital EDSR’.
“Usually microwave antennas are designed to provide a pure magnetic field,” says Dr. Tanttu. “But this particular antenna design produced more electric fields than we had hoped for, but that turned out to be lucky as we discovered a new effect that could be used to manipulate qubits. I did. It’s a coincidence for you.”
Building for Quantum Computing on Silicon
Professor of Quantum Engineering Sciences at UNSW and CEO and founder of Diraq, Professor Andrew Dzurak, said: Professor Dzurak led the team that built the first quantum logic gate in silicon in 2015.
“This builds on our work to enable quantum computing in silicon, based on essentially the same semiconductor component technology as existing computer chips, rather than relying on exotic materials.
“Because it is based on the same CMOS technology used in the computer industry today, our approach makes it easier and faster to scale up to commercial production, producing billions of qubits on a single chip. You will be able to achieve your goal of
CMOS (or Complementary Metal Oxide Semiconductor, pronounced “seemos”) is the manufacturing process at the heart of modern computers. It is used to make all kinds of integrated circuit components including microprocessors, microcontrollers, memory chips and other digital logic circuits as well as analog circuits such as image sensors and data converters.
Building a quantum computer has been called the “21st century space race.” This is a difficult and ambitious challenge that has the potential to provide innovative tools for tackling otherwise impossible computations, such as the design of complex pharmaceuticals and advanced materials, and rapid exploration. . Large, unsorted databases.
“We often think of the moon landing as humanity’s greatest technological marvel,” said Professor Jurrac. “But the truth is that today’s CMOS chips—billions of operating devices integrated to act like a symphony and carry in your pocket—are an amazing technological achievement that will revolutionize modern life. Quantum computing will be just as amazing.”
Original: Quantum chips with billions of qubits become more accessible with new spin control method
Than: University of New South Wales
