Serge Haroche of the College of France, Paris, and David Wineland of the National Institute of Standards and Technology in Boulder, Colorado, have been awarded an equal share of this year’s Nobel Prize in Physics.
While Wineland used light to measure the quantum state of atoms, Haroche used as a sensitive probe of light particles trapped in a cavity. Both of these techniques have been applied to investigate the fundamentals of quantum mechanics, and might lead to the development of quantum computers or incredibly precise atomic clocks.
Particles of light and matter can occupy several mutually exclusive states simultaneously. Particles will show their quantum nature only in complete isolation, and even the tiniest interference can destroy it. The act of measuring itself can be enough to disrupt some systems. These new techniques allowed quantum physicists to probe at these states without destroying them.
Haroche bounced microwave photons between a pair of superconducting mirrors, and sent a stream of rubidium atoms through the fog of photons. The measurement of the spin of the atoms as they entered and exited the mirrored cavity allowed him to indirectly probe the quantum properties of the microwave photons inside. Progressive measurements have allowed his team to observe a photon’s quantum wavefunction, which simultaneously describes all of its possible quantum states, and monitor its collapse into a single, well-defined state.
Wineland’s team trapped beryllium ions in electrical fields and cooled them with a laser that excited the ion’s electrons, sucking vibrational energy from the system and thus lowering the overall temperature. Then, they used lasers to alter the vibrations between ions, which allowed them to control the quantum interactions inside the system. This work has already been used to create atomic clocks with unprecedented accuracy, and could also be used in a quantum computer.
These new techniques developed by Haroche and Wineland have allowed researchers to isolate, study, and manipulate increasingly complex quantum systems.