# IBM's Eagle quantum computer just beat a supercomputer at complex math

IBM's Eagle quantum computer has outperformed a conventional supercomputer when solving complex mathematical calculations. This is also the first demonstration of a quantum computer providing accurate results at a scale of 100+ qubits, a company press release said.

Qubits, short for quantum bits, are analogs of a bit in quantum computing. Both are the primary or smallest units of information. However, unlike bits that can exist in two states, 0 or 1, a qubit can represent either of the states or in a superposition where it exists in any proportion of the two states.

Scientists have been working on using superposition to compute large amounts of information in a fraction of the time it would take on a supercomputer. However, since the superposition can be disturbed by even the slightest interference from the outside environment, quantum computers are error-prone.

## Working with the noise

Scientists have been looking to secure computing environments and work with as few qubits as possible to reduce interference. In the recent past, though, researchers have instead started favoring working with the 'noise' since increasing the number of qubits has exponential advantages.

Recently, *Interesting Engineering* reported how Chinese researchers used their photonic quantum computer Jiuzhang to solve a mathematical problem in less than a second. The same on the fastest supercomputer would have taken at least five years to solve.

Now a team of researchers led by Abhinav Kandala at IBM used a similar approach and decided to test the abilities of their "noisy" quantum computer against a conventional supercomputer at the Lawrence Berkeley National Laboratory in California.

The Eagle quantum computer used by the team had 127 qubits, and both computers were asked to calculate the most likely behavior of a collection of particles, such as atoms with a spin arranged in a grid and interacting with each other.

## When the supercomputer failed

The researchers found that the equations could be solved exactly for a certain number of particles. However, as the number of particles in the puzzle increased, methods such as approximation were needed to compute the solution, and the results of both machines agreed. Finally, though, the calculations became so complex that the supercomputer could no longer handle them.

The Eagle quantum computer, though continued to churn out numbers. Although the team did not have any means to test if the results were accurate, the results agreed with established calculations.

Even as this was the first time a quantum computer with more than 100 qubits had been demonstrated to work correctly, the research team is nowhere near claiming quantum supremacy. That would be the stage where quantum computers achieve levels that are impossible to accomplish for supercomputers.

IBM, which is building supercomputers, expects the technology to improve and add to its ability in the coming years. It is, however, also testing quantum processors, which are expected to be crucial in computing solutions in material science, healthcare, and physics.

The company has also confirmed that its Quantum Systems at on-site locations and available over the cloud will now be powered by a minimum of 127 bits, bringing higher computing power to the research community.

IBM's findings were published as the cover story in the journal, *Nature*

**Abstract**

Quantum computing promises to offer substantial speed-ups over its classical counterpart for certain problems. However, the greatest impediment to realizing its full potential is noise that is inherent to these systems. The widely accepted solution to this challenge is the implementation of fault-tolerant quantum circuits, which is out of reach for current processors. Here we report experiments on a noisy 127-qubit processor and demonstrate the measurement of accurate expectation values for circuit volumes at a scale beyond brute-force classical computation. We argue that this represents evidence for the utility of quantum computing in a pre-fault-tolerant era. These experimental results are enabled by advances in the coherence and calibration of a superconducting processor at this scale and the ability to characterize1 and controllably manipulate noise across such a large device. We establish the accuracy of the measured expectation values by comparing them with the output of exactly verifiable circuits. In the regime of strong entanglement, the quantum computer provides correct results for which leading classical approximations such as pure-state-based 1D (matrix product states, MPS) and 2D (isometric tensor network states, isoTNS) tensor network methods2,3 break down. These experiments demonstrate a foundational tool for the realization of near-term quantum applications4,5.

***

Listen to our recent Lexicon podcast about quantum computing with Dr Shohini Ghose below: