Christopher D. Hamley

Observation of spinor dynamics in optically trapped 87Rb Bose-Einstein condensates.

We measure spin mixing of F=1 and F=2 spinor condensates of 87Rb atoms confined in an optical trap. We determine the spin mixing time to be typically less than 600 ms and observe spin population oscillations. The equilibrium spin configuration in the F=1 manifold is measured for different magnetic fields and found to show ferromagnetic behavior for low field gradients. An F=2 condensate is created by microwave excitation from the F=1 manifold, and this spin-2 condensate is observed to decay exponentially with time constant 250 ms. Despite the short lifetime in the F=2 manifold, spin mixing of the condensate is observed within 50 ms.

Cavity QED with optically transported atoms

Ultracold

Spin-nematic squeezed vacuum in a quantum gas

^{87}\mathrm{Rb}\phantom{\rule{0.3em}{0ex}}\text{atoms}

Non-equilibrium dynamics of an unstable quantum pendulum explored in a spin-1 Bose-Einstein condensate

are delivered into a high-finesse optical microcavity using a translating optical lattice trap and detected via the cavity field. The atoms are loaded into an optical lattice from a magneto-optic trap and transported

Strong quantum spin correlations observed in atomic spin mixing.

1.5\phantom{\rule{0.3em}{0ex}}\mathrm{cm}

Nondestructive fluorescent state detection of single neutral atom qubits.

into the cavity. Our cavity satisfies the strong-coupling requirements for a single intracavity atom, thus permitting real-time observation of single atoms transported into the cavity. This transport scheme enables us to vary the number of intracavity atoms from

Photoassociation spectroscopy of a spin-1 Bose-Einstein condensate

1\phantom{\rule{0.5em}{0ex}}\text{to}\phantom{\rule{0.5em}{0ex}}g100

Dynamic Stabilization of a Quantum Many-Body Spin System

corresponding to a maximum atomic cooperativity parameter of 5400, the highest value ever achieved in an atom-cavity system. When many atoms are loaded into the cavity, optical bistability is directly measured in real-time cavity transmission.

Parametric excitation and squeezing in a many-body spinor condensate

Squeezed states—which permit precision beyond the scope of Heisenberg’s uncertainty relation—are well established for spin-1/2 particles. Now an elegant demonstration of squeezing in spin-1 condensates generalizes the criteria for squeezed states to higher spin dimensions.

All-Optical Atomic Bose-Einstein Condensates

A pendulum prepared perfectly inverted and motionless is a prototype of unstable equilibrium and corresponds to an unstable hyperbolic fixed point in the dynamical phase space. Here, we measure the non-equilibrium dynamics of a spin-1 Bose-Einstein condensate initialized as a minimum uncertainty spin-nematic state to a hyperbolic fixed point of the phase space. Quantum fluctuations lead to non-linear spin evolution along a separatrix and non-Gaussian probability distributions that are measured to be in good agreement with exact quantum calculations up to 0.25 s. At longer times, atomic loss due to the finite lifetime of the condensate leads to larger spin oscillation amplitudes, as orbits depart from the separatrix. This demonstrates how decoherence of a many-body system can result in apparent coherent behaviour. This experiment provides new avenues for studying macroscopic spin systems in the quantum limit and for investigations of important topics in non-equilibrium quantum dynamics.