China Claims Breakthrough in Quantum Computing Race

The trade war rivalry between USA and China is well known. However, since the past few years, both the nations are caught up in a heated tech race towards supremacy. This is also reflected with China putting its best to lead in terms of quantum computing power too.

Last year, Google grabbed headlines, when it announced Sycamore quantum computer had achieved quantum advantage—formerly known as quantum supremacy. Sycamore could perform computation in 200 seconds that would take the fastest supercomputers about 10,000 years. Recently, China developed a quantum computing system which is reported to be 10 billion times faster than Google's Sycamore. Researchers from the University of Science and Technology of China explained that this quantum computer prototype named Jiuzhang delivered results in minutes calculated to take more than 2 billion years of effort by the world's third-most-powerful supercomputer.

According to the Science journal, Jiuzhang can detect up to 76 photons through Gaussian boson sampling, a standard simulation algorithm, which uses particles of light sent through an optical circuit, measuring the output. Boson sampling was devised by Scott Aaronson and Alex Arkhipov in 2011 as an experimental way to prove a quantum advantage.  Here the probability distribution of many bosons (a fundamental particle that includes photons) is calculated. The probability of detecting a boson at a given position can be calculated from an equation in many unknowns.

The Chinese researchers team claim Jiuzhang can process 10 billion times faster than Google's Sycamore. Further, this achievement marks that China's first milestone on its mission to attain full-scale quantum computing.

Lu Chaoyang, a professor in charge of the experiment at USTC stated that Jiuzhang achieved the breakthrough by manipulating particles of light. This is different than the approach used by Google, who used supercold, superconducting metal, to build quantum circuits to manipulate qubits. Qubits or Quantum Bits is synonymous to binary bits of classical computer, but unlike binary bits, it can exist in many states simultaneously.

A similar approach is also leveraged by IBM. Both tech giants have invested large sums of money into superconducting circuits to push quantum computing research.  Meanwhile, Honeywell and IonQ have been developing alternative quantum computing architectures that involve trapping ions. Moreover, Australia's Silicon Quantum Computing uses spin-based silicon qubits for its quantum systems.

In the case of Google's Sycamore, 54 qubits were used, which were cooled to fractions of a degree above absolute zero. Only one qubit didn't work but the remaining 53 were enough to demonstrate supremacy over conventional computers on a carefully chosen statistical problem.

In comparison, for Jiuzhang the research team led by quantum physicist Jian-Wei Pan at the University of Science and Technology of China, built a large tabletop setup consisting of lasers as the light source and beam splitters to help create the individual photons, along with hundreds of prisms and dozens of mirrors to provide the randomized paths for the photons to travel. Wired mentions that each photon read out at the end of the process can be thought of as is roughly equivalent to reading out a qubit on a processor like Google's, revealing the result of a calculation.

The researchers equipped Jiuzhang with 300 beam splitters and 75 mirrors. Up to 76 output photon-clicks were observed while average detected photon number by the prototype is 43, during experimental runs lasting 200 seconds. Comparatively, Chinese supercomputer, TaihuLight, would have taken 2.5 billion years to arrive at the same result.

Jiuzhang cannot be used immediately in real-life applications. It will need to work with a programmable chip to perform various calculations. Also addressing the rumors about threat it poses to cryptocurrency, or any encryption used by finance, communication and government systems currently; Jiuzhang is reported to be unable to solve the factoring problem that is crucial to decoding encrypted information.

China has invested heavily in quantum computing, with Xi Jinping's government spending US$10 billion on the country's National Laboratory for Quantum Information Sciences.