There were many doubts as to whether or not quantum computing could ever become a reality. The circuitry relies on tricky manipulation of ions and photons, or otherwise requires temperatures near absolute zero. It is, by all means and purposes, an immense test of mankind’s cleverness and aptitude for innovation. Yet just 3 days ago a machine in a provincial part of what is an ambitious and newly-empowered China has, for the second time in human history, shown quantum supremacy.
Quantum supremacy is a demonstration that a quantum computer can achieve something which would otherwise be impossible for a classical computer. The first instance of this occurred in 2019 when Google’s Sycamore processor was able to complete a calculation in just over 3 minutes; the same calculation would have taken a classical computer 10,000 years to complete. The claim was later disputed by rival company IBM, stating that it wouldn’t have taken one of their supercomputers more than 3 days — not 10,000 years — to get the same result. No one has yet come forward to dispute China’s newest claim to quantum supremacy, however. Its figures are even more astounding than those of Sycamore.
The Chinese quantum computing system, called Jiuzhang, completed in 200 seconds what they estimate one of the world’s most powerful supercomputers would have taken 2 billion years to solve. The supercomputer in question was China’s Sunway TaihuLight, the third fastest in the world. This puts Jiuzhang’s quantum advantage at 10¹⁴. The results were published Thursday, December 3rd.
With this estimate it is reasonable to say that no classical computer could have accomplished what Jiuzhang did on that remarkable autumn day. While Google’s quantum circuitry was based on incredibly cold superconducting loops, the Chinese team’s quantum circuits were created using photons (packets of light). These photons carried quantum data through optical circuits while their path was manipulated via mirrors. At the end of the process, the photon was read and this data contributed to the final calculation. This is the equivalent of one of Google’s 53 qubits (quantum bits) being read. The qubits, in this case, were photons. One of the best advantages of using photons over superconducting loops is that they can be kept at room temperature instead of at just a few degrees above absolute zero.
Jiuzhang’s calculation was a solve for the boson-sampling problem — a result that, beyond just being a useful tool to achieve quantum advantage, can also someday serve a practical use in machine learning and quantum chemistry. However, unlike Google’s Sycamore processor, Jiuzhang was created with the boson-sampling problem already in mind. It was essentially built to do this specific calculation. It is non-programmable and, consequently, doesn’t yet have any practical uses. If it does one day achieve programmability then it could simulate molecules and help revolutionize several of the world’s top industries, as is the goal of all quantum computers.
But it’ll be a while before Jiuzhang, or any other quantum computer on Earth, demonstrates true practical or commercial applications. For that to happen we must go far beyond the double-digit numbers of qubits in today’s quantum computers. At least hundreds of qubits — and possibly millions — will be needed before these quantum machines can fulfill their true potential.
As I recently discussed in my more thorough article, China and the US are in a tense race to be the first to advance this new technology. Each country has security concerns in mind as quantum computers’ powerful processors threaten to break our internet’s current encryption. This means important financial records and government communications are vulnerable to cyberattacks. While the US has so far dominated the advancement of quantum computing, China has invested $10 billion into becoming the world’s center for quantum research. Right on track with its goal to reach supremacy by 2020, China is making good on its promise to compete fiercely against the EU and US.
But, researchers note, no matter which country achieves advanced quantum computing first, it will be a gift to mankind all the same. Those who have doubted this new generation of computers are confronted with the impressive results of two quantum processors flickering away — both in very different regions of the world, both attempting to revolutionize it.