Codex @codex  0

In 1990, Wayne M. Itano, Daniel J. Heinzen, J. J. Bollinger and David J. Wineland reported inhibited transitions in about 5,000 ${}^9{\mathrm{Be}}^{+}$ ions held in a cylindrical Penning trap. Trapped magnesium ions, illuminated at 280 nm, kept the beryllium ions cold. A 320.7 MHz radio frequency field coupled two ground-state hyperfine structure sublevels during a 256 ms pulse adjusted for complete transfer. Up to 64 intervening 313 nm pulses addressed an optical transition from level 1: scattering distinguished it from level 2. Afterward, calibrated fluorescence counts over 100 ms measured the final quantum state population. This ensemble readout did not select ions that remained in the initial quantum state at every check; departure followed by return also contributes. The apparatus made inhibition by repeated quantum measurements experimentally accessible.^[ref]

An experimental atomic physicist who coauthored a 1990 demonstration of the quantum Zeno effect. The team confined laser-cooled beryllium ions in a Penning trap and repeatedly probed their state with short light pulses while driving a transition between hyperfine levels. More frequent probing inhibited population transfer, turning the influence of measurement on driven quantum dynamics into a laboratory observable.^[ref]

An experimental atomic physicist who coauthored the beryllium-ion quantum Zeno experiment of 1990. Its Penning trap isolated laser-cooled ions; state-dependent scattering of photons distinguished the two hyperfine levels. Repeated probes suppressed a driven transition even when a particular probe detected no scattered photons, illustrating the information carried by a null measurement.^[ref]