Physical Review A

Compensation of noise in optical lattices via feedback: Low-temperature limit

T. Yu. Ivanova, D. A. Ivanov

Published Feb 13, 2008• 2 citations

Abstract

We consider the problem of suppression of noise acting on atomic ensembles trapped in optical lattices in the low-energy limit. Noise affecting external degrees of freedom of each atom independently and noise influencing only the center-of-mass (c.m.) mode of the ensemble are addressed. Taking into account the quantum character of the atomic motion, we show that negative feedback loop acting on the c.m. coordinate of the atomic ensemble is able to partially compensate both noise sources mentioned above.

DOI: 10.1103/physreva.77.025402

Related papers

Quantum Limits of Feedback Cooling in Optical Lattices

T. Yu. Ivanova

A quantum-mechanical analysis of feedback cooling [see Phys. Rev. Lett. 94 , 153002 (2005)] of atoms trapped in a far-off-resonant optical lattice is presented. The model considered is valid for ultralow energies of atoms, thus, allowing for the study of an ultimate cooling limit. The influence of the measurement-induced noise and feedback-induced atom-atom correlations on the cooling efficiency is discussed. It is shown that there are regimes where the quantum noise can be effectively compensated for.

Journal of Experimental and Theoretical Physics LettersJan 1, 20059 citations

Feedback stabilization of atoms in an optical lattice

T. Yu. Ivanova, D. A. Ivanov

The feasibility of using feedback for stabilization of atoms in an off-resonance optical lattice is demonstrated. In the proposed scheme, the collective coordinate of atoms is measured and instantaneously compensated for via a spatial shift of the potential of the optical lattice. An external action that provides for heating of atoms with subsequent decrease in their lifetime in the lattice is simulated by a set of independent reservoirs, each interacting only with one atom. A quantum-mechanical analysis of the problem shows that the use of the feedback within the proposed scheme makes it possible to stabilize the energy of atoms at a level below the equilibrium energy.

Optics and SpectroscopyAug 1, 20070 citations

Effect of correlations on feedback control of atoms

T. Yu. Ivanova, D. A. Ivanov

We discuss the influence of atom-atom correlations on the collective feedback of atoms trapped in an 1D optical lattice. Analytically deriving the dynamics of these correlations we consider a series of feedback steps and analyze the average energy change as a measure of the feedback efficiency. It is demonstrated that the correlations strongly affect the feedback process, so that without destroying them the energy of the system can not be effectively reduced. The situations when a correlation-destroying mechanism operates are discussed as well.

Laser Physics LettersAug 9, 20062 citations

Bloch oscillations of cold atoms in a cavity: Effects of quantum noise

B. Prasanna Venkatesh, Duncan H J O’Dell

We extend our theory of Bloch oscillations of cold atoms inside an optical cavity [Venkatesh et al., Phys. Rev. A 80, 063834 (2009)] to include the effects of quantum noise arising from coupling to external modes. The noise acts as a form of quantum measurement backaction by perturbing the coupled dynamics of the atoms and the light. We take it into account by solving the Heisenberg-Langevin equations for linearized fluctuations about the atomic and optical mean fields and examine how this influences the signal-to-noise ratio of a measurement of external forces using this system. In particular, we investigate the effects of changing the number of atoms, the intracavity lattice depth, and the atom-light coupling strength, and show how resonances between the Bloch oscillation dynamics and the quasiparticle spectrum have a strong influence on the signal-to-noise ratio, as well as heating effects. One of the hurdles we overcome in this paper is the proper treatment of fluctuations about time-dependent mean fields in the context of cold-atom cavity QED.

arXiv:1212.3594Physical Review AJul 29, 201317 citations

Motional dephasing of atomic clock spin waves in an optical lattice

S. D. Jenkins, T Zhang, T. A. B. Kennedy

In a cold atomic ensemble the weak Raman scattering of an incident laser beam writes a spin-wave grating by transferring an atom between ground-level hyperfine states. These spin-waves serve as a basis for a quantum memory. For clock states, where magnetic dephasing is suppressed, thermal motion of the atoms across the spin-wave is the principal source of dephasing on the sub-millisecond timescale, limiting the quantum memory time achievable. An investigation of the role of the optical lattice in reducing motional dephasing is presented, using Monte Carlo simulations to study the influence of ensemble temperature, trap depth and differential ac Stark shifts in the case of rubidium.

Journal of Physics B Atomic Molecular and Optical PhysicsJun 8, 201224 citations

Interfacing ultracold atoms and mechanical oscillators

Stephan Camerer

In this thesis I present experiments investigating controlled coupling between mechanical oscillators and ultracold atoms. I report on three different coupling mechanisms. In a first experiment, the surface potential experienced by atoms close to the mechanical oscillator is employed to couple the oscillator motion to the center of mass (COM) motion of a trapped Bose-Einstein condensate (BEC). The magnetic trapping potential is modified by the surface potential arising from the oscillator surface which results in a reduced trap depth. Vibration of the oscillator leads to a modulation of the trap frequency and the minimum of the trapping potential. Observing the loss of atoms from the BEC allows us to read out the amplitude of the mechanical oscillator with the atoms. In a second experiment, we study the coupling of a mechanical membrane oscillator and thermal atoms trapped in a 1D optical lattice. The membrane is the end mirror of the lattice, and oscillation of the membrane couples to the COM mode of the atomic ensemble. Conversely, the center of mass motion of the atomic ensemble redistributes photons between the two running waves forming the 1D optical lattice, effectively modulating their power, and hence the radiation pressure acting onto the membrane. We observe the action of the oscillating membrane onto the atoms by detecting the resulting temperature increase of the atomic ensemble in absorption imaging. To observe the backaction of the atoms onto the mechanical oscillator, the mechanical damping is measured in experiments with and without atoms in the lattice, and we measure higher damping in the presence of atoms in agreement with the theoretical predictions. These experiments are the first demonstration of backaction of an atomic system onto a mechanical oscillator. We investigate a third coupling mechanism, where the motion of a mechanical oscillator is coupled to the collective spin of a BEC. The tip of a mechanical oscillator is functionalized with a magnet, which transduces the oscillators' motion into oscillations of the magnetic field. This drives spin-flip transitions of trapped atoms to untrapped motional states. The coupling strength is not limited by the square root of the mass ratio of atoms and oscillator as in the other coupling schemes discussed in this thesis. We investigate this coupling scheme theoretically, and discuss the realization of a nanometer-sized mechanical oscillator with a magnetic island. I report on the status of the fabrication, and propose a simplified fabrication method.

Jan 1, 20110 citations