30 research outputs found
Quantum statistics of overlapping modes in open resonators
We study the quantum dynamics of optical fields in weakly confining
resonators with overlapping modes. Employing a recently developed quantization
scheme involving a discrete set of resonator modes and continua of external
modes we derive Langevin equations and a master equation for the resonator
modes. Langevin dynamics and the master equation are proved to be equivalent in
the Markovian limit. Our open-resonator dynamics may be used as a starting
point for a quantum theory of random lasers.Comment: 6 pages, corrected typo
Quantum Langevin theory of excess noise
In an earlier work [P. J. Bardroff and S. Stenholm], we have derived a fully
quantum mechanical description of excess noise in strongly damped lasers. This
theory is used here to derive the corresponding quantum Langevin equations.
Taking the semi-classical limit of these we are able to regain the starting
point of Siegman's treatment of excess noise [Phys. Rev. A 39, 1253 (1989)].
Our results essentially constitute a quantum derivation of his theory and allow
some generalizations.Comment: 9 pages, 0 figures, revte
Quantum state manipulation of trapped atomic ions
A single laser-cooled and trapped 9Be+ ion is used to investigate methods of
coherent quantum-state synthesis and quantum logic. We create and characterize
nonclassical states of motion including "Schroedinger-cat" states. A
fundamental quantum logic gate is realized which uses two states of the
quantized ion motion and two ion internal states as qubits. We explore some of
the applications for, and problems in realizing, quantum computation based on
multiple trapped ions.Comment: Postscript only. 21 pages text, 5 figures., Proc. Workshop on Quantum
Computing, Santa Barbara, CA, Dec. 1996, Submitted to Proc. Roy. Soc.
Theory for the photon statistics of random lasers
A theory for the photon statistics of a random laser is presented. Noise is
described by Langevin operators, where both fluctuations of the electromagnetic
field and of the medium are included. The theory is valid for all lasers with
small outcoupling when the laser cavity is large compared to the wavelength of
the radiation. The theory is applied to a chaotic laser cavity with a small
opening. It is known that a large number of modes can be above threshold
simultaneously in such a cavity. It is shown the amount of fluctuations is
increased compared to the Poissonian value by an amount that depends on that
number
Positive-P and Wigner representations for quantum-optical systems with nonorthogonal modes
We generalize the basic concepts of the positive-P and Wigner representations to unstable quantum-optical systems that are based on nonorthogonal quasimodes. This lays the foundation for a quantum description of such systems, such as, for example an unstable cavity laser. We compare both representations by calculating the tunneling times for an unstable resonator optical parametric oscillator
Quantum mechanical counterpart of nonlinear optics
Raman-type laser excitation of a trapped atom allows one to realize the
quantum mechanical counterpart of phenomena of nonlinear optics, such as
Kerr-type nonlinearities, parametric amplification, and multi-mode mixing.
Additionally, huge nonlinearities emerge from the interference of the atomic
wave function with the laser waves. They lead to a partitioning of the phase
space accompanied by a significantly different action of the time evolution in
neighboring phase-space zones. For example, a nonlinearly modified coherent
"displacement" of the motional quantum state may induce strong amplitude
squeezing and quantum interferences.Comment: 6 pages, 4 figures, to be published in Phys. Rev. A 55 (June
Quantum Nondemolition State Measurement via Atomic Scattering in Bragg Regime
We suggest a quantum nondemolition scheme to measure a quantized cavity field
state using scattering of atoms in general Bragg regime. Our work extends the
QND measurement of a cavity field from Fock state, based on first order Bragg
deflection [9], to any quantum state based on Bragg deflection of arbitrary
order. In addition a set of experimental parameters is provided to perform the
experiment within the frame work of the presently available technology.Comment: 11 pages text, 4 eps figures, to appear in letter section of journal
of physical society of Japa
Determination of entangled quantum states of a trapped atom
We propose a method for measuring entangled vibronic quantum states of a
trapped atom. It is based on the nonlinear dynamics of the system that appears
by resonantly driving a weak electronic transition. The proposed technique
allows the direct sampling of a Wigner-function matrix, displaying all knowable
information on the quantum correlations of the motional and electronic degrees
of freedom of the atom. It opens novel possibilities for testing fundamental
predictions of the quantum theory concerning interaction phenomena.Comment: 7 pages, 3 figures, to be published in Phys. Rev. A 56 (Aug
Field quantization for open optical cavities
We study the quantum properties of the electromagnetic field in optical
cavities coupled to an arbitrary number of escape channels. We consider both
inhomogeneous dielectric resonators with a scalar dielectric constant
and cavities defined by mirrors of arbitrary shape. Using
the Feshbach projector technique we quantize the field in terms of a set of
resonator and bath modes. We rigorously show that the field Hamiltonian reduces
to the system--and--bath Hamiltonian of quantum optics. The field dynamics is
investigated using the input--output theory of Gardiner and Collet. In the case
of strong coupling to the external radiation field we find spectrally
overlapping resonator modes. The mode dynamics is coupled due to the damping
and noise inflicted by the external field. For wave chaotic resonators the mode
dynamics is determined by a non--Hermitean random matrix. Upon including an
amplifying medium, our dynamics of open-resonator modes may serve as a starting
point for a quantum theory of random lasing.Comment: 16 pages, added references, corrected typo