An experiment has been published in the scientific journal Nature Communications that proposes a fundamentally new way to confirm that quantum computers can indeed outperform ordinary classical machines. The central problem the work addresses is verification: as the number of operations grows, checking the results of a quantum device on a regular PC becomes practically impossible due to the excessive demands on computational power. The researchers proposed a workaround in the form of an experimental “game” based on a complement sampling task, and the fresh experiment showed that the quantum system handled the task more effectively than the best classical algorithms.
How the complement sampling “game” works
The essence of the proposed test is simple in formulation but difficult for a classical machine. All possible answer options are secretly divided into two equal groups — A and B. The participant’s goal is to obtain one random option from group A and return an answer belonging to group B. For a classical computer this turns out to be a trap: the system receives only a single specific digit or element and does not know the distribution of the remaining options, so its chances of success drop as the size of the data increases. A quantum computer, by contrast, thanks to superposition can exist in multiple states simultaneously, process the entire group A in parallel, transform it into group B using a special circuit, and only then perform the measurement.
Why classical machines cannot do this
The difference in approaches leads to a gap in computational efficiency that classical algorithms cannot compensate for by scaling up resources. As the task scales, the classical system faces exponential growth in memory and time requirements, whereas the quantum device uses state parallelism to bypass direct enumeration. This is precisely what makes the proposed test a convenient verification tool: it allows one to pinpoint the moment when the result of a quantum device becomes unreachable for any classical approach, even in theory.
The 55-qubit experiment
The researchers tested the algorithm on the Quantinuum H2 trapped-ion quantum computer, applying thousands of different circuits and scaling the experiment up to 55 qubits. Despite the presence of hardware noise characteristic of real devices, the quantum system’s results were statistically unreachable for any classical PC. In particular, in a test with 37-bit strings the quantum computer solved a task that lies beyond the capabilities of the best classical algorithms, and the difference in computational efficiency turned out to be substantial.
What’s next: two quantum computers and a quantum channel
The authors also outline the next stage of the method’s development. In the future they plan to complicate the experiment by separating the answer-selection and answer-analysis systems onto two distinct quantum computers connected by a genuine quantum communication channel. Such a transition from a single device to a distributed configuration will allow verifying advantage under conditions close to real quantum networks and further strengthen the evidentiary basis of verification.
Context: where this fits in the bigger picture
The obtained result fits into the broader context of the race to prove quantum advantage, where other directions are developing in parallel. For instance, in a related line of work the Jupiter supercomputer previously fully simulated a 50-qubit quantum processor, demonstrating the growing capabilities of classical simulation. It is important, however, that this is a separate achievement and not part of the described experiment: the complement sampling test published in Nature Communications and the 55-qubit experiment on the Quantinuum H2 represent a standalone verification method in which a quantum device solves a task that is statistically unreachable for classical algorithms.
