Jiuzhang 4.0, China’s latest photonic quantum computer, is staking a claim to quantum supremacy. The photonic supercomputer completed a complex calculation in microseconds, which the world’s fastest supercomputer would take 10^42 years to complete. 

Often referred to as the next frontier of computing, quantum computers are being sought to complete calculations that are impossible for classical computers. Scientists hope that quantum computers will help us solve problems like climate change and accelerate drug discovery. 

At the core of quantum computing are quantum bits, or qubits, that can store multiple values simultaneously, unlike binary bits that can only be a 0 or a 1. This exponentially increases their ability to carry out complex calculations. 

While the US-led research has focused on the use of superconducting qubits for these computations, China’s Jiuzhang uses a photonic approach, where light particles instead of superconducting qubits are used for computations. 

What is Jiuzhang? 

First unveiled in 2020, the Jiuzhang machine was the world’s first photonic system to demonstrate the quantum computational advantage. Under the leadership of quantum physicist Pan Jianwei, the machine development has advanced rapidly, with Jiuzhang 4.0 unveiled earlier this week. 

According to reports, the 4.0 operates with 1,024 squeezed-state inputs across an 8,176-mode interferometric network. The system can manipulate and detect 3,050 photons at once, which is 10 times more than its predecessor. 

Researchers at the University of Science and Technology of China (USTC), where the Jiuzhang machine is built, tasked the 4.0 machine with completing a Gaussian boson sampling. As per estimates, the El Capitan, the world’s fastest supercomputer in the US, would take 10^42 years to complete this sampling. The Jiuzhang 4.0 completed it in mere microseconds. 

Not just speed, the machine also achieved 92 percent source efficiency and 51 percent overall system efficiency. This is important, since photon loss is a major issue with photonic quantum computers and a major bottleneck in advancing this technology further. 

Claim to quantum supremacy

With this achievement, China looks to stake a claim to achieving quantum supremacy. But not everyone is convinced. The US-led initiative on quantum computers focuses on developing fault-tolerant, programmable devices capable of running commercial applications. 

China’s Jiuzhang, though, is a highly specialized quantum computer and excels only in specialized tasks such as Gaussian boson sampling. While classical supercomputers running today can handle a wide variety of tasks, Juizhang isn’t like them. Yet. Jiuzhang’s achievements are hard to ignore. 

Jiuzhang may not be a versatile quantum computing system, but its rapid advancements, such as an order-of-magnitude increase in scale over previous iterations, are commendable. 

“No realistic classical computing resources, to our knowledge, can bring the MPS [matrix product state] algorithm anywhere near the accuracy achieved by our experiment,” the researchers said in a statement. 

Even though Jiuzhang 4.0 might not be the ultimate quantum computer built to date, it does demonstrate China’s leadership in quantum computing. Even if Jiuzhang excels at achieving high accuracy and performance on a single specialized task, China could rapidly develop similar specialized systems for various tasks in drug discovery, artificial intelligence, and even defense applications in the future.