15 research outputs found
Cavity-assisted measurement and coherent control of collective atomic spin oscillators
We demonstrate continuous measurement and coherent control of the collective
spin of an atomic ensemble undergoing Larmor precession in a high-finesse
optical cavity. The coupling of the precessing spin to the cavity field yields
phenomena similar to those observed in cavity optomechanics, including cavity
amplification, damping, and optical spring shifts. These effects arise from
autonomous optical feedback onto the atomic spin dynamics, conditioned by the
cavity spectrum. We use this feedback to stabilize the spin in either its high-
or low-energy state, where, in equilibrium with measurement back-action
heating, it achieves a steady-state temperature, indicated by an asymmetry
between the Stokes and anti-Stokes scattering rates. For sufficiently large
Larmor frequency, such feedback stabilizes the spin ensemble in a nearly pure
quantum state, in spite of continuous measurement by the cavity field.Comment: 5 pages, 4 figures, and supplemental materia
Ponderomotive light squeezing with atomic cavity optomechanics
Accessing distinctly quantum aspects of the interaction between light and the
position of a mechanical object has been an outstanding challenge to
cavity-optomechanical systems. Only cold-atom implementations of cavity
optomechanics have indicated effects of the quantum fluctuations in the optical
radiation pressure force. Here we use such a system, in which quantum
photon-number fluctuations significantly drive the center of mass of an atomic
ensemble inside a Fabry-Perot cavity. We show that the optomechanical response
both amplifies and ponderomotively squeezes the quantum light field. We also
demonstrate that classical optical fluctuations can be attenuated by 26 dB or
amplified by 20 dB with a weak input pump power of < 40 pW, and characterize
the optomechanical amplifier's frequency-dependent gain and phase response in
both the amplitude and phase-modulation quadratures
Quantum Measurement with Atomic Cavity Optomechanics
A cloud of ultracold atoms trapped within the confines of a high-finesse optical cavity shakes from the pressure of the light that probes it. This form of measurement backaction, a central component of quantum measurement theory, is the subject of this dissertation. Enlisting the collective motion of ultracold atoms as the mechanical degree of freedom in a cavity optomechanical system, we reach settings cold and quiet enough to allow for the effects of measurement backaction to manifest. We report predictions for and experimental observa- tions of the Standard Quantum Limit for force sensitivity, optical ponderomotive squeezing, and the possibility of complex squeezing through generalized optical correlations