In quantum mechanics, measuring a particle usually disturbs it, making high-precision control very difficult. Wineland levitated ions in an RF trap, laser-cooled them to near absolute zero, and used laser pulses to prepare superpositions of ground and excited states. Haroche built a superconducting microwave cavity that stores a photon for a tenth of a second and sent giant Rydberg atoms through it to count photons without destroying them. These achievements realized quantum-nondemolition (QND) measurements and drastically reduced read-out errors for qubits. Their methods underpin basic quantum-logic gates, optical lattice clocks, and other emerging technologies. Extended coherence times and reliable entanglement were demonstrated, opening paths toward quantum communication and sensing. The results are expected to have broad impact on future information technology and fundamental physics.

Quantum-nondemolition measurement and coherent control are central to quantum information science. Wineland laser-cooled single ions in a Paul trap to the motional ground state using side-band cooling, then used Raman pulses to entangle internal and motional degrees of freedom, demonstrating the first two-qubit gate. This approach evolved into segmented-electrode architectures for scalable ion-trap quantum computers. Haroche confined microwave photons in a superconducting cavity with Q > 10⁹ and exploited phase shifts of traversing Rydberg atoms to perform photon-number-resolving QND detection, enabling time-resolved studies of Schrödinger-cat decay. Both techniques contribute to measurements beyond the standard quantum limit and quantitative tests of decoherence theory while providing building blocks for photon memories and hybrid quantum networks. Wineland’s Al⁺ optical clock reached a fractional uncertainty of 10⁻¹⁷, opening precision tests of general relativity and geodesy. Collectively, the laureates’ work laid crucial foundations for the second quantum technology revolution.

Wineland formed Coulomb crystals in RF Paul traps, achieved n = 0 via side-band cooling, and implemented Mølmer–Sørensen gates with >99 % fidelity, meeting thresholds for fault-tolerant QC. Quantum-logic spectroscopy on Al⁺ optical clocks read clock transitions through auxiliary ion fluorescence, reaching 10⁻¹⁸ systematic uncertainty. Haroche employed Nb superconducting cavities (Q ≈ 10¹⁰, g/2π ≈ 50 kHz) and exploited the giant dipole moment of Rydberg atoms for single-photon QND detection and vacuum Rabi oscillation observation. Quantum-jump tracking of cavity photons in 2008 yielded decoherence constants via Quantum Trajectory analysis. Both technologies merge back-action-evading measurement with Hamiltonian engineering, bridging fault-tolerant computation and precision metrology. Ion-chain Ising simulators and cavity-based photon memories derived from their work underpin designs for scalable quantum networks.