THE QUANTUM ADVANTAGE v

Jadavpur University Science Club
Dec 28, 2020
3 min read

- ANANNYO DEY

UG1

In the early 1980s, Richard Feynman proposed that a quantum computer would be an effective tool to solve problems in physics and chemistry, given that it is exponentially costly to simulate large quantum systems with classical computers.

A team of researchers at the University of Copenhagen has recently reached a milestone on the path to realizing Feynman’s vision, towards full-scale quantum computing. Just when Google had claimed to have achieved "quantum supremacy" for the first time in October 2019. Researchers at the University of Copenhagen’s Niels Bohr Institute in collaboration with the University of Bochum, joined Google in the race to build the world’s first quantum computer!

WHY QUANTUM?

In classical computers, the unit of information ‘bit’ can be either 1 or 0. But its quantum equivalent - the ‘qubit’- can be both at the same time. This phenomenon opens the door for multiple calculations to be performed simultaneously. But the qubits need to be synchronized using a quantum effect known as entanglement, which Albert Einstein termed "spooky action at a distance".

Scientists have been working on quantum computers for decades because they promise much faster speeds, but they’ve struggled to build working devices with enough qubits to surpass the performance of conventional devices.

AND THE RACE BEGINS…

Google's fully programmable 53-working qubit ‘Sycamore’ quantum processor was able to perform a specific “random-sampling” task in 200 seconds, which they claimed would take the world's best supercomputer 10,000 years to complete.

IBM argued that an ideal simulation of the same task can be performed on a classical system in 2.5 days and with far greater fidelity. Although it was certainly an impressive milestone, we were still decades away from an actual quantum computer that could solve problems we're interested in.

"We now possess the tool that makes it possible to build a quantum simulator that can outperform a classical computer. This is a major breakthrough and the first step into uncharted territory in the world of quantum physics," asserts one of the Copenhagen researchers, Prof. Peter Lodahl, Director of the Hy-Q.

The researchers developed a nanochip less than one-tenth the thickness of a human hair, capable of producing hundreds of photons that can be used to store huge amounts of data in the form of quantum information. That can be used as hardware in tomorrow’s quantum computers, much in the same way that electrical transistors are used in today’s conventional computers.

THE ADVANTAGE

By scaling up the technology, these nanochips may achieve what is known as 'quantum advantage': the state where a quantum device can solve a given computational task faster than the world's most powerful supercomputer.

The researchers are yet to conduct an actual 'quantum advantage' experiment (to be able to control 50 qubits in a comprehensive set-up), because that Google’s 10 million Euro- project is well beyond the university’s own financial means. But they’ve proved their chip produces a quantum mechanical resource- the fundamental building block, that can be used to reach this state with already demonstrated technology.

The advantage of such quantum computers is that we already have the technology for scaling up, because of the availability of advanced photonic chips (developed for the telecom industry). A major challenge to generating photon qubits was to do so with sufficiently high quality. This is precisely where the Copenhagen researchers achieved their breakthrough.

"In the meantime, we will use our photon sources to develop new and advanced quantum simulators to solve complex biochemical problems that might, for example, be used to develop new medicines. So, we are already preparing the next steps for the technology…" continues Peter Lodahl.

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