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In a dark room, a whisper is barely audible. To make out the words, you need to get close, or set up many sensitive microphones. That's roughly the reasoning behind the new work: the authors place quantum "ears" right inside a resonator, where a high-frequency gravitational wave turns into an electromagnetic echo.

Ordinary detectors, like giant interferometers, can't hear gravitational waves in the gigahertz range — the frequency is just too high. A different approach is needed. The setup features a strong static magnetic field. When a gravitational wave passes through it, a weak electric field is born: this is the inverse Gertsenshtein effect. The resonator amplifies the signal, and tiny superconducting qubits, quantum systems with two levels, sit at points where the field is strongest. Each qubit acts like a sensitive microphone, ready to pick up the vibration.

But the real breakthrough lies in how the qubits work together. They are entangled into a symmetric Dicke state: all qubits behave as a single entity. Then the signal doesn't just add up: its probability grows quadratically with the number of qubits. The sensitivity to the wave amplitude improves according to a law close to the inverse 3/4 power of the number of qubits. 800 qubits in an ideal network give a gain of one hundred thousand times over the limit of an ordinary resonator. This is a decisive step: gravitational interaction is suppressed by the Planck scale, but the collective quantum effect breaks through that wall.

This gives birth to a new-generation detector for high-frequency gravitational waves. It could peer into the era right after the big bang or pick up signals from exotic objects. The dark room of the early universe is no longer silent.