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Alain Aspect, Jean Dalibard and Gérard Roger tested Bell inequalities using pairs of photons and rapidly changing polarization analyzers. An acousto-optical switch in each arm routed light toward one of two polarizers; switching near $50\mathrm{MHz}$ changed the effective setting on a timescale shorter than the photon transit time between the analyzers. The measured correlations violated the tested Bell inequality. These switches were driven at incommensurate frequencies, so their role should be distinguished from the independently randomized settings of later experiments.^[ref]

A physicist researching quantum optics and the foundations of quantum mechanics.^[ref]

In 1982, Alain Aspect, Jean Dalibard and Gérard Roger used a calcium cascade and an acoustic standing wave in water to route each photon toward one of two fixed polarizers. Switching took about $10\mathrm{ns}$, against $40\mathrm{ns}$ for light to cross between stations. Photomultiplier coincidence circuit rates, with delayed-background subtraction and polarizer-removal normalization, violated their Bell inequality. Supplementary polarizers checked each channel against Malus's law. The timing attacked the locality loophole, but the authors emphasized that switching was quasiperiodic, not random; incomplete switching and inefficient collection also limited the test. Its normalized statistic differs from the CHSH inequality convention used below.^[ref]

1992 conference manuscript, reproduced in 2008. By Yvan Castin, Jean Dalibard and Klaus Mølmer.

Verified sections 1–2, equations (4)–(16): conditional jump/no-jump evolution and ensemble equivalence.

Claude Cohen-Tannoudji developed methods for controlling atomic internal states and motion with light. With Jean Dalibard, he explained how polarization gradients produce laser cooling below the simple Doppler cooling limit.

The essential link is between a spatially changing atomic light shift and state-changing optical pumping. The pumping delays let moving chemical atoms lose kinetic energy through repeated transitions between different light-shift potentials. This supplied a microscopic explanation for unexpectedly low experimental temperatures.^[ref]

Jean Dalibard developed, with Claude Cohen-Tannoudji, models explaining laser cooling below the simple Doppler cooling limit. Spatially changing wave polarization makes the light shifts of atomic sublevels vary with position.

In Sisyphus cooling, moving chemical atoms climb a light-shift potential and are optically pumped into a lower-energy sublevel. Repeating that sequence removes kinetic energy. The mechanism depends on internal-state structure and optical pumping, explaining why a two-level Doppler model misses the additional cooling.^[ref]

Klaus Mølmer helped develop a wave-function description of dissipative quantum evolution with Yvan Castin and Jean Dalibard. Their 1992 manuscript, reproduced in 2008, represents individual conditioned evolutions through stochastic jumps and intervening nonunitary evolution.^[ref]

Averaging many trajectories recovers the corresponding Lindblad equation. This quantum-trajectory unravelling connects an ensemble density operator with possible individual measurement records; the trajectory depends on how the environment is monitored.

Polarization-gradient cooling uses spatial variation in electromagnetic polarization together with optical pumping between internal quantum states to cool moving chemical atoms.

Jean Dalibard and Claude Cohen-Tannoudji distinguish cooling by changing elliptical polarization from cooling by rotating linear polarization. The hill picture below concerns the former.^[ref]

In 2006, Zoran Hadzibabic, Peter Krüger, Marc Cheneau, Baptiste Battelier and Jean Dalibard split a cooled rubidium-87 cloud into two independent planar gases using an optical lattice. After release, the expanding sheets overlapped; absorption imaging recorded their matter-wave interference. Smooth fringe waviness revealed thermal phase fluctuations, while sharp dislocations indicated isolated vortices. The initial evaporative-cooling endpoint controlled the preparation; central fringe contrast served as a degeneracy proxy because direct thermometry in the lattice was difficult.^[ref]

Loss of extended coherence coincided with increased vortex signatures. The optical trap and finite cloud produced a crossover; tightly bound pairs were unresolved, and short-wavelength modes could contaminate high-temperature counts. These were observations of the vortex-unbinding mechanism, not a direct measurement of phase stiffness or a sharp homogeneous universal stiffness jump. The authors left the sample's superfluidity open.^[ref]

Yvan Castin, with Jean Dalibard and Klaus Mølmer, formulated a stochastic wave-function approach to dissipative quantum systems. Their construction samples conditional jumps and no-jump evolution so that the ensemble reproduces a density-operator master equation.^[ref]

Using state vectors can reduce the cost of numerical simulations compared with directly storing a full density matrix, although many trajectories may be needed for precise averages. The 2008 posting reproduces a 1992 manuscript and explicitly acknowledges earlier related quantum-filtering work.