Marco Scigliuzzo

A quantum bit is like a tuning fork that rings at its own frequency. To find out its state, you place a microphone-resonator nearby. Usually, the tuning fork and the microphone are connected via a spring-like capacitor: sound gets through, but the tuning fork also starts vibrating from external noise and can get knocked off.

A regular computer amplifies a signal like a megaphone amplifies a voice. But a megaphone doesn't work for a quantum computer: it distorts the whisper too much. And the whisper here is the signal from qubits, the cells of quantum memory. The signal is so weak that any extra noise drowns it out.