Quantum computing moves a step closer to solving our most complex problems

Researchers have devised a temperature control technique that can keep quantum bits stable longer
Field could drive new discoveries in healthcare, energy, environmental science

Science

Holly Chik

Published: 8:00pm, 14 Oct, 2022

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One of the biggest challenges for scientists in the field of quantum computers is how to keep the tiny particles they study working together longer.

Now, a group of researchers in Britain, China and the United States have developed a temperature control technique that could soon help solve the kinds of complex problems that stump today’s smartest computers.

The researchers used the technique to extend the time that a group of quantum bits – basic units of information in quantum computing known as qubits – can retain their quantum uniqueness to represent both zero and one at the same time.

The mechanism, known as Quantum Many-Body Scarring (QMBS), is said to be a key step towards potential applications in quantum sensing and metrology, where more qubits can work together to boost the accuracy of measurements, including magnetic and electric fields.

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Scientists say that quantum computing could someday propel new discoveries in fields like healthcare, energy, and environmental science.

In traditional computing, a bit represents either zero or one as its basic unit of information. A qubit goes a step further. It can represent zero, one or both at the same time – one of the simplest expressions of the peculiarity of quantum mechanics.

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Since the basic information of a quantum computer can represent all possibilities simultaneously, they are theoretically much faster and more powerful than the regular computers we use in our daily lives.

But the subatomic particles at the heart of the technology are fragile, short-lived and prone to error if exposed to even a slight disturbance from the surroundings. That means quantum computers must be operated in extremely cold and isolated environments.

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In physics, the process of thermalisation means physical bodies reach a thermal equilibrium through mutual interaction. When that happens in quantum computing, all coherent information - coherence - is lost as equilibrium is established across a quantum space. In other words, the quantum state is ended.

To tackle the problem, researchers used QMBS to delay thermalisation in a chain of 30 qubits. During the test, a superconducting processor operated in an environment of 0.02 Kelvin (-273.13 degrees Celsius), close to absolute zero – the lowest temperature possible.

The QMBS mechanism delays the thermalisation that ends the quantum state. Photo: Handout

The researchers were able to achieve coherence for 1,000 nanoseconds – 10 times longer than without the control technique.

The team from Zhejiang University in Hangzhou, the Chinese Academy of Sciences in Beijing, the University of Leeds in Britain, and Boston-based start-up QuEra Computing and Arizona State University in the US published their findings in the peer-reviewed journal Nature Physics on Thursday.

Study co-author Ying Lei, an assistant professor at Zhejiang University’s school of physics, told the Post that assembling a larger chain of qubits to work in coordination could lead to more efficient operations and calculations in quantum computers.

“For example, a company with two or three employees is rather easy to manage. But in larger companies with hundreds of workers, some might have better relationships with one another, while others compete with each other,” he said, referring to how qubits work. “In the quantum world, when interactions become chaotic, it leads to thermalisation.”

“Ideally, qubits should be in order, like ducks that swim in a row, following a pattern, so that they can be operated efficiently to perform calculations and other tasks,” Ying said.

To build a quantum computer that has a significant advantage over classic computers, Ying said a machine must have at least 1,000 high-quality qubits that work together in a stable quantum state.

The difficulty starts with the environment. Disturbances in an environment can lead to errors, so a quantum computer might require millions of qubits to protect the quantum information from errors that result from a loss of coherence, according to Ying.

Quantum physicists are now working to increase the number of high-quality qubits that can operate in a chain – to hundreds and maybe even a thousand.

“A scalable system that extends the coherence time of qubits will be extremely useful when future computers with more qubits are built,” Ying said.