Quantum computing company Quantinuum recently announced a quantum computer that it claims has outperformed Google’s supercomputer by 100 times.
Google’s 2019 result uses a specific test called the linear cross-entropy benchmark in an attempt to demonstrate quantum supremacy, the point at which quantum computers outperform state-of-the-art ordinary (or classical) computers.
What exactly is quantum computer?
Quantum computers work with quantum bits. Quantum bits (qubits for short) are like ordinary computer bits, except that their values can be both 0 and 1 at the same time. Thanks to this quantum quirk, computers can think of 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 ordinary computers. This is because their qubits are often supercooled atoms arranged in an array. Cooled to such an extent, the atoms enter a quantum state. The moment the value of any of the qubits is certain, the quantum state is decohered and the quantum operation breaks down. For this reason, quantum computers as they currently exist are only in specialized research and laboratory settings.
What did the quantum computer Quantinuum do?
The Quantinuum computer beat a landmark 2019 achievement by Google’s Sycamore processor, which took about 200 seconds to complete a task that would have taken a state-of-the-art classical supercomputer about 10,000 years.
To achieve the 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 release by Quantinuum, its quantum computer also performed its algorithm with about 30,000 times less power than it would take a classical computer to perform the operation.
Importantly, the Quantinuum computer achieved a new record for cross-entropy, 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 1) your results. Google’s 2019 cross-entropy benchmark score was ~.002; The H2-1 score was ~.35. “Unlike past reports related to XEB experiments, 35% is a significant step toward the idealized fidelity limit of 100%, where the computational advantage of quantum computers is clearly visible,” Quantinuum said in a statement. 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—the way humans store and move data, as well as compute new information. Last year, a different team of researchers showed how quantum computers can perform calculations in a way that closely resembles time travel.
“The experiment we describe seems impossible to solve with standard (non-quantum) physics that obeys the normal arrow of time,” David Arvidsson-Shukkur, a quantum physicist at the University of Cambridge and lead author of the study, told Gizmodo at . “Thus, it appears that quantum entanglement can generate instances that effectively look like time travel.”
The previous year, another team claimed to have succeeded in creating a quantum wormhole, a portal through which quantum information can travel instantaneously.
Quantinuum also runs the news circuit (no pun intended). In 2022, a team using a Quantinuum computer managed to create a new phase of matter by blasting the qubits with lasers reading the Fibonacci sequence.
Quantum computing sometimes reads like science fiction because it seems so strange to tap into the realm beyond classical physics to do complex calculations. But the systems keep getting better and their applications are diverse (although some border on pipe dreams). For now, this has been relegated to research settings, but quantum computers are slowly creating the world of tomorrow today.
