Quantum computing company Quantinuum recently announced a quantum computer that the company claims has surpassed the performance of a groundbreaking computer from Google by a factor of 100.
Google’s 2019 results used a specific test, called the linear cross-entropy benchmark, in an attempt to demonstrate quantum superiority, the point at which quantum computers outperform state-of-the-art conventional (or classical) computers.
What exactly is a quantum computer?
Quantum computers operate on quantum bits. Quantum bits (qubits for short) are similar to regular computer bits, except that their values can be 0 and 1 at the same time. This quantum quirk allows computers to consider more solutions to a problem faster than a classical computer. Ultimately, quantum computers should be able to solve problems that classical computers cannot.
But quantum computers don’t look like regular computers. That’s because their qubits are often supercooled atoms, arranged in an array. When they’re so cooled, the atoms enter a quantum state. The moment the value of one of the qubits is certain, the quantum state decoheres and the quantum operation breaks down. For that reason, quantum computers as they exist today are used only in special research and laboratory settings.
What did the Quantum quantum computer do?
The Quantinuum computer surpassed a key feat of Google’s 2019 Sycamore processor, which took about 200 seconds to complete a task that would take a classical supercomputer about 10,000 years.
To achieve this result, the Quantinuum team upgraded its H2-1 processor from a 32-qubit system to a 56-qubit system, greatly increasing its computing power. According to a press release from Quantinuum, its quantum computer also ran its algorithm using about 30,000 times less power than a classical computer would have needed to perform the operation.
Importantly, the Quantinuum computer set a new record for the cross entropy benchmark, a metric used to compare the performance of different quantum computers. The benchmark measures the power of the quantum system; the noisier the system, the worse (closer to zero than to 1) your results will be. Google’s 2019 score on the cross entropy benchmark was ~.002; H2-1’s score was ~.35. “Contrary to previous announcements related to XEB experiments, 35% is a significant step toward the idealized 100% confidence limit where the computational advantage of quantum computers is clearly in view,” according to a Quantinuum press release. The team’s research is currently hosted on the arXiv preprint server.
What else do quantum computers do?
Quantum computers are testbeds for the future of information, that is, the way people store and move data and calculate new information. Last year, another team of researchers showed how quantum computers could perform calculations in a way that looks a lot like time travel.
“The experiment we describe seems impossible to solve with standard (non-quantum) physics, which follows the normal arrow of time,” David Arvidsson-Shukur, a quantum physicist at the University of Cambridge and lead author of the study, told Gizmodo at the time. “So it seems that quantum entanglement can generate instances that effectively look like time travel.”
The year before, another team claimed they had succeeded in creating a quantum wormhole: a portal through which quantum information could travel instantaneously.
Quantinuum has also made headlines (no pun intended). In 2022, a team using a Quantinuum computer managed to create a new phase of matter by bombarding the qubits with lasers that read out the Fibonacci sequence.
Quantum computing sometimes reads like science fiction, because it seems so strange to use the realm outside of classical physics to perform complex calculations. But the systems are getting better and better, and their applications are diverse (although some border on pie-in-the-sky). For now, it’s relegated to research environments, but quantum computers are slowly creating the world of tomorrow today.