Quantum jumps of sound.

Quantum jumps between energy levels of a nanomechanical resonator were observed with 85% fidelity, demonstrating discrete energy transitions in a massive vibrating object.

• Why it matters: Understanding and measuring energy quantization in macroscopic systems bridges the gap between quantum mechanics and classical physics, revealing fundamental quantum behavior in tangible objects.
• What they did: A superconducting qubit was dispersively coupled to a nanomechanical resonator, enabling repeated quantum nondemolition measurements of phonon number and heralding single-phonon states.
• The result: The experiment captured quantum jumps, confirming the quantized nature of mechanical energy states and paving the way for advanced quantum control of massive systems.