Are Photonic Quantum Computers the Future?

A little more than a year after Google claimed Quantum Supremacy , something weird has happend. China is claiming new light-based quantum computer Jiuzhang has achieved quantum supremacy at many orders of magnitude better.

The promise of quantum computers is that certain computational tasks might be executed exponentially faster on a quantum processor than on a classical processor. If the report on Jiuzhang is accurate, a second type of quantum device performed a calculation impossible for a traditional computers a few billion times better.

The term “quantum supremacy” to describe the point where quantum computers can do things that classical computers can’t. Typically this involves some possibly useless calculation that can be done in seconds that would take the world’s most powerful supercomputers of today something like 10,000 years to complete.

So as new forms of Quantum Supremacy are arrived at, it doesn't necessarily mean that these are machines that will be useful. So what the heck happend and is it real? The last Thursday on December 3rd, 2020, China’s leading quantum research group made its own declaration of quantum supremacy, in the journal Science. A system called Jiuzhang produced results in minutes calculated to take more than 2 billion years of effort by the world’s third-most-powerful supercomputer.

This would make China's claim that its photonic Quantum machine a quantum computer that’s 10 billion times faster than Google’s.

Google’s computer, however, is based on superconducting materials, not photons.

Still even for the future of artificial intelligence, one has to wonder at possible future applications with Quantum computers. Named Jiuzhang after an ancient Chinese mathematical text, the new quantum computer can perform a calculation in 200 seconds that would take more than half a billion years on the world’s fastest non-quantum, or classical, computer. It's not clear when Quantum computers will be either useful, mainstream or commercially accessible.

It's almost hard to wrap your head around. Jiuzhang consists of a complex array of optical devices that shuttle photons around. Those devices include light sources, hundreds of beam splitters, dozens of mirrors and 100 photon detectors. But it sounds just like a novelty. Jiuzhang generates a distribution of numbers that is exceedingly difficult for a classical computer to replicate. 

Since China is not a data transparent state, all the headlines began with "China Claims". In era when Chinese stocks in the U.S. are not audited by U.S. auditors, it's literally hard to tell what is real and what is not when it comes to China's businesses and accomplishments. Artificial intelligence and quantum computing are no exception.

The researchers said that using a process called “Gaussian boson sampling”, their Jiuzhang prototype quantum computer took a little over three minutes to complete a task that the world’s fastest conventional machine would not be able to complete in 600 million years. Should we applaud, or speculate upon the real world utility?

Scenario

1. Photons are first sent into a network of channels. There, each photon encounters a series of beam splitters, each of which sends the photon down two paths simultaneously, in what’s called a quantum superposition.
2. Paths also merge together, and the repeated splitting and merging causes the photons to interfere with one another according to quantum rules.
3. Finally, the number of photons in each of the network’s output channels is measured at the end.
4. When repeated many times, this process produces a distribution of numbers based on how many photons were found in each output.
5. If operated with large numbers of photons and many channels, the quantum computer will produce a distribution of numbers that is too complex for a classical computer to calculate. In the new experiment, up to 76 photons traversed a network of 100 channels.

I think it's certainly a demonstration of novel thinking. While Google achieved its iteration of Quantum Supremacy (which was disputed by IBM) using quantum circuits using supercold, superconducting metal, the team at University of Science and Technology of China, in Hefei, recorded its result by manipulating photons, particles of light.

In theory employing quantum computers to give an AI quick access to trillions more data points could supercharge its accuracy and usefulness, for instance in predicting the probability of something. In general, Quantum computers rely on some counter-intuitive physics of the subatomic world, and are extremely fragile and difficult to maintain.

The potential power of quantum computers springs from their basic building blocks, dubbed qubits. Like the bits of conventional computers, they can represent 0s and 1s of data; but qubits can also exploit quantum mechanics to attain an unusual state called a superposition that encapsulates the possibilities of both. 

Currently the morbid calculations used are calculations that are esoteric ones designed to be difficult for classical computers. Lately many nation states like to compete in developing the fastest supercomputers and this feels no different, with little foreseeable application to AI and the future of deep learning, machine learning or algorithms.

Still what might happend to the field of artificial intelligence when we we're able to get enough qubits to work together in harmony and with stability? With enough qubits it’s possible to take computational shortcuts conventional computers can’t—an advantage that grows as more qubits work together. Quantum Supremacy is an arrogant phrase, but one wonders if photonic quantum computers might hold the key.

Demonstrating quantum supremacy with a different type of device reveals how rapidly quantum computing is progressing and it is notable China has accomplished the feat. The calculation the Jiuzhang performed, might have legit consequences on the social credit and surveillance state China is developing. For instance in data mining, bioinformatics and finance, the researchers themselves stated.

Professor Pan Jianwei built something pretty unique. The Jiuzhang could be one of the most complex optical instruments ever built, with 25 crystals, each tailor-made and maintained at precise temperature, to manipulate the photons and simulate real-life chaos. It does show humanity is willing to experiment with new kinds of computational machines. Scott Aaronson, a computer science professor with the University of Texas, Austin, came up with the original idea of a light-based quantum computer.

China is a likely forerunner in the future of Quantum computing and notably Quantum encryption. The Chinese team was led by Jian-Wei Pan, whose sizable research team has benefited from a Chinese government effort to be more prominent in quantum technology.

If you enjoyed this article, you might like some of our other articles at the Last Futurist.