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Two days ago, Google astonished many people around the world with claims that they have achieved a major milestone in quantum computing, one which has largely been an unattainable feat until now.

In a paper titled “Quantum supremacy using a programmable superconducting processor”, Google explains how its 53-bit quantum computer named ‘Sycamore’ took only 200 seconds to perform a sensitive computation that would otherwise take the world’s fastest supercomputer 10,000 years. This, Google claims is their attainment of ‘quantum supremacy’. If confirmed, this would be the first major milestone in harnessing the principles of quantum mechanics to solve computational problems.

Google’s AI Quantum team and John Martinis, physicist at the University of California are the prime contributors to this achievement. NASA Ames Research Center, Oak Ridge National Laboratory and Forschungszentrum Jülich have also helped Google in implementing this experiment.

In quantum computing, quantum supremacy is the potential ability of any device to solve problems that classical computers practically cannot. According to Sundar Pichai, Google CEO, “For those of us working in science and technology, it’s the “hello world” moment we’ve been waiting for—the most meaningful milestone to date in the quest to make quantum computing a reality.” This announcement from Google comes exactly one month after the same paper was leaked online.

However, following Google’s announcement, IBM is arguing “an ideal simulation of the same task can be performed on a classical system in 2.5 days with far greater fidelity.” According to IBM, as proposed by John Preskill in 2012, the original meaning of the term “quantum supremacy,” is the point where quantum computers can do things that classical computers can’t. Since, Google has not yet achieved this threshold, IBM argues that their claims are wrong.

IBM says that in the published paper, Google has assumed that the RAM storage requirements in a traditional computer would be massive. However, if a different approach of using both RAM and hard drive space to store and manipulate the state vector is employed, the 10,000 years specified by Google will drop considerably.

Thus, IBM refutes Google’s claims and stated that in its strictest definition, the quantum supremacy standard has not been met by anybody until now. IBM believes that “fundamentally, quantum computers will never reign “supreme” over classical computers, but will rather work in concert with them, since each have their unique strengths.” 

IBM further added that the term ‘supremacy’ is currently being misunderstood and urged everybody in the community to treat Google’s claims “with a large dose of skepticism.”

Read More: Has IBM edged past Google in the battle for Quantum Supremacy?

Though Google has not directly responded to IBM’s accusations, in a statement to Forbes, a Google spokesperson said, “We welcome ideas from the research community on new applications that work only on NISQ-era processors like Sycamore and its successors. We’ve published our circuits so the whole community can explore this new space. We’re excited by what’s possible now that we have this unique new resource.”

Although IBM is skeptical of Google’s claims, the news of Google’s accomplishment is making waves all around the world.

Google’s experiment with the Sycamore processor

To achieve this milestone, Google researchers developed Sycamore, the high-fidelity quantum logic gates processor consisting of a two-dimensional array of 54 transmon qubits. Sycamore consists of a two-dimensional grid where each qubit is connected to four other qubits. Each qubit in the processor is tunably coupled to four nearest neighbors, in a rectangular lattice and are forward-compatible for error correction. As a result, the chip has enough connectivity to let  the qubit states quickly interact throughout the entire processor. This feature of Sycamore is what makes it distinct from a classical computer.

Image Source: Google blog

In the Sycamore quantum processor, “Each run of a random quantum circuit on a quantum computer produces a bitstring, for example 0000101. Owing to quantum interference, some bit strings are much more likely to occur than others when we repeat the experiment many times. However, finding the most likely bit strings for a random quantum circuit on a classical computer becomes exponentially more difficult as the number of qubits (width) and number of gate cycles (depth) grow,” states John Martinis, Chief Scientist Quantum Hardware and Sergio Boixo, Chief Scientist Quantum Computing Theory, Google AI Quantum.

Image Source: Google blog

For the experiment, the Google researchers ran a random simplified circuit from 12 to 53 qubits with the circuit depth kept constant. Next, they checked the performance of the quantum computer using classical simulations and compared the performance of a quantum computer with a theoretical model. After verifying that the quantum system was working, the researchers ran a random hard circuit with 53 qubits and this time, allowed the circuit depth to expand until the point where the classical simulation became infeasible. At the end, it was found that this quantum computation cannot be emulated on a classical computer and hence, this opens “a new realm of computing to be explored,” says Google.

The Google team is now working on quantum supremacy applications like quantum physics simulation, quantum chemistry, generative machine learning, and more. After procuring “certifiable quantum randomness”, Google is now working on testing this algorithm to develop a prototype that can provide certifiable random numbers.

Leaving IBM’s accusation aside, many people are excited about Google’s great achievement.

Few people believe that Google is making a hullabaloo of a not-so-successful experiment.

A user on Hacker News comments, “Summary: – Google overhyped their results against a weak baseline. This seems to be commonplace in academic publishing, especially new-ish fields where benchmarks aren’t well-established. There was a similar backlash against OpenAI’s robot hand, where they used simulation for the physical robotic movements and used a well-known algorithm for the actual Rubik’s Cube solving. I still think it’s an impressive step forward for the field.”

Check out the video of Google’s demonstration of quantum supremacy below.

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