In the superconducting circuits that make up quantum computers, extra particles, quasiparticles, are born from time to time. They are like random passersby who barge into the processor's work and spoil the calculations. Scientists have learned to catch these events in real time on two neighboring qubits — superconducting elements sensitive to charge. Both qubits are connected to a common waveguide, like two microphones in the same room: if something happens nearby, both hear it.

In a calm mode, quasiparticles tunnel (leak through the energy barrier) only a few times per second. But about once a minute, a burst occurs: within thousandths of a second, the rate jumps by a factor of a thousand. Such bursts last about 7 milliseconds, like a short ring in silence. And most importantly: both qubits hear this ring almost simultaneously, meaning that errors from quasiparticles are correlated, that is, they arise in several places at once.

The authors also noticed rare events where a burst is accompanied by a charge shift on the qubit — about once an hour. This is as if a guest not only entered the room but also moved the furniture. Understanding such correlations will help build quantum processors that make fewer mistakes — because now we can see when and where the noise comes from.