Google Claims Quantum Supremacy

The race to build the world's first useful quantum computer is nearing its end.  Google says an advanced computer has achieved "quantum supremacy" for the first time, surpassing the performance of conventional devices. 

Google has officially announced its new quantum computing in an Nature article published on 23rd October. Google unveiled the world's largest quantum computer processor to date. Dubbed Bristlecone, it's a 72-qubit gate-based superconducting system that claims to blow the previous best, IBM's 50-qubit processor, out of the water. 

The technology giant's Sycamore quantum processor was able to perform a specific task in 200 seconds that would take the world's best supercomputers 10,000 years to complete. Scientists have been working on quantum computers for decades because they promise much faster speeds.

In classical computers, the unit of information is called a "bit" and can have a value of either 1 or 0. But its equivalent in a quantum system, the qubit (quantum bit), can be both 1 and 0 at the same time. This phenomenon opens the door for multiple calculations to be performed simultaneously.

But the qubits need to be synchronised using a quantum effect known as entanglement, which Albert Einstein termed "spooky action at a distance". Scientists have struggled to build working devices with enough qubits to make them competitive with conventional types of computer.

Sycamore contains 54 qubits, although one of them did not work, so the device ran on 53 qubits. In their Nature paper, John Martinis of Google  and colleagues set the processor a random sampling task, where it produces a set of numbers that has a truly random distribution.

Sycamore was able to complete the task in three minutes and 20 seconds. By contrast, the researchers claim in their paper that Summit, the world's best supercomputer, would take 10,000 years to complete the task. However, IBM, which has been working on quantum computers of its own, questioned some of Google's figures.

"We argue that an ideal simulation of the same task can be performed on a classical system in 2.5 days and with far greater fidelity," IBM researchers Edwin Pednault, John Gunnels, and Jay Gambetta said in a blog.  

"This 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."

They also queried Google's definition of quantum supremacy and said it had the potential to mislead.

"First because... by its strictest definition the goal has not been met. But more fundamentally, because quantum computers will never reign 'supreme' over classical computers, but will rather work in concert with them, since each have their unique strengths."

Google and IBM aren’t the only companies trying to be first in the race to quantum supremacy. 

Microsoft has its own quantum computing research division while Intel is putting quantum computer processors on silicon chipsand several startups, like Rigetti, are at the cutting-edge as well. 

Quantum and the Future of Computing
In the early 1980s, Richard Feynman proposed that a quantum computer would be an effective tool with which to solve problems in physics and chemistry, given that it is exponentially costly to simulate large quantum systems with classical computers. Since then, computer scientists have some formidable hurdles to overcome to make quantum computers useful and commonplace. But with tech firms investing heavily, about $1bn (£780m) to date, with more in the pipeline, many researchers are now confident that rudimentary devices will be put to good use, in combination with standard computers, in the next decade or so.

Quantum computers lend themselves to problems that are essentially too demanding for classical computers to take on.

One area where scientists expect them to make an impact is in drug discovery. Quantum computers should run these searches much faster by analysing whole libraries of molecules at a time and identifying the most promising drug candidates.
Several startups see quantum computers as a means to design radically new materials, including better batteries, by modelling the quantum behaviour of the subatomic particles inside them.

Another area where the sheer processing capability of quantum computers could prove itself is weather forecasting. The science and art of forecasting have steadily improved with greater computing power, but quantum computers could mean a step change in forecasting accuracy. Inevitably, quantum computers will also be used for financial modelling where a huge number of variables dictate the movements of markets.

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