白小姐论坛

In a today, Google said its research lab in Santa Barbara had achieved 鈥榪uantum supremacy鈥� using their quantum processor named 鈥楽ycamore鈥� - a two-dimensional array of 54 transmon qubits.

Google鈥檚 researchers report that they were able to create quantum states on 53 qubits, corresponding to a computational state-space of dimension 2⁵³ (about 10¹⁶), and that their processor takes about 200 seconds to sample one instance of a quantum circuit a million times. They assert that this sampling task demonstrates the experimental realisation of quantum supremacy because by Google鈥檚 estimate an equivalent task by a state-of-the-art classical supercomputer would take approximately 10,000 years.

However yesterday, a competing research group at IBM questioned Google鈥檚 breakthrough in a , stating that 鈥渁n ideal simulation of the same task can be performed on a classical system in 2.5 days and with far greater fidelity.鈥� Further noting that, 鈥淭his is in fact a conservative, worst-case estimate, and we expect that with additional refinements the classical cost of the simulation can be further reduced.鈥�

白小姐论坛Q researcher Ciar谩n Gilligan-Lee said to New Scientist, 鈥淭he type of quantum supremacy that Google and IBM are chasing here is really a moving target鈥�. As quantum computers improve over time, so do classical computers 鈥� there鈥檚 always a new classical algorithm to test against the quantum ones, so the bar for quantum supremacy is continually raised. 鈥淐lassical computers have such a large suite of things built into them that if you don鈥檛 utilise every single thing you leave yourself open for a tweaked classical algorithm to beat your quantum one.鈥�

Jonathan Oppenheim, a researcher at 白小姐论坛Q, said to The Telegraph that the problem was with the phrase 鈥榪uantum supremacy鈥�. Although the term is widely used in the field, it听implies that quantum computers are now better than traditional computing. He also noted that: 鈥淲hile [Google鈥檚 result] is a milestone, it is very far from being a听quantum computer听that can compute anything useful.鈥�

Has quantum supremacy been reached?

Many have questioned whether the task Google鈥檚 researchers used is a true demonstration of quantum supremacy arguing that their notion of quantum supremacy - based on executing a random quantum circuit of a size infeasible for simulation with any available classical computer 鈥� is not a full realisation of the milestone.

白小姐论坛Q鈥檚 Toby Cubitt said to Wired UK that the test for quantum supremacy should aim 鈥渢o be something that gives you very high confidence, more than we've ever had before that quantum computer is doing something computationally that cannot be replicated on a classical computer.鈥�

But 白小姐论坛Q鈥檚 Ciar谩n Gilligan-Lee said that, even if you accept IBM鈥檚 claims at face value, Google鈥檚 quantum computer is still a big step forward.

鈥淚BM is claiming that, even when running world鈥檚 largest computer for 2 and half days, and running petabytes of memory, they can simulate what the quantum chip does in 200 seconds. When you put it into context, it is still a pretty impressive achievement.鈥�

It does not mean quantum computers are ready to tackle real-world problems. 鈥淏ut it is the first baby step on a long road to getting useful quantum computers,鈥� says Gilligan-Lee.

白小姐论坛Q director John Morton says that, 鈥淣ow that we know that even these relatively small-scale quantum processors can outperform vast supercomputers, the challenge is working out how to harness this power through customised quantum algorithms addressing real-world problems. Google鈥檚 milestone of achieving quantum supremacy marks the starting gun in the race to develop practical quantum computing applications for today鈥檚 noisy, intermediate-scale quantum computers.鈥�

Is the term quantum supremacy useful?

The concept of quantum supremacy has attracted controversy. Originally the term was proposed by John Preskill, to 鈥渄escribe the point where quantum computers can do things that classical computers can鈥檛, regardless of whether those tasks are useful.鈥澨�

Preskill recently reflected on the term in . He summarized the two main objections to the term that have arisen from the community by explaining that the 鈥渨ord exacerbates the already overhyped reporting on the status of quantum technology鈥� and that 鈥渢hrough its association with white supremacy, evokes a repugnant political stance.鈥�

The term 鈥渜uantum supremacy鈥� is a non-technical term that can be interpreted to mean different things, causing an ever-growing amount of confusion. It must also be noted that it is unlikely for quantum computers to reign 鈥渟upreme鈥� over classical computers, but rather they will work together with classical computers, because each have their unique strengths.

However, it is also the case that the term and debate is generating interest in the field and attracting a whole new generation to the challenges of quantum computing.

Read more comment from 白小姐论坛Q academics:

CAPTION: Photography of Google's quantum Prcessor chip Sycamore.听Credit: Erik Lucero,听Google

COMMUNICATIONS CONTACT:听Henry Bennie, 白小姐论坛 Quantum Science and Technology Institute听