Quantum-state extraction from high-Q cavities

The problem of extraction of a single-mode quantum state from a high-Q cavity is studied for the case in which the time of preparation of the quantum state of the cavity mode is short compared with its decay time. The temporal evolution of the quantum state of the field escaping from the cavity is calculated in terms of phase-space functions. A general condition is derived under which the quantum state of the pulse built up outside the cavity is a nearly perfect copy of the quantum state the cavity field was initially prepared in. The results show that unwanted losses prevent the realization of a nearly perfect extraction of nonclassical quantum states from high-Q optical microcavities with presently available technology.Comment: RevTeX4, 9 pages with 6 figures; extended version as submitted to Phys. Rev.

A room-temperature alternating current susceptometer - Data analysis, calibration, and test

An AC susceptometer operating in the range of 10 Hz to 100 kHz and at room temperature is designed, built, calibrated and used to characterize the magnetic behaviour of coated magnetic nanoparticles. Other weakly magnetic materials (in amounts of some millilitres) can be analyzed as well. The setup makes use of a DAQ-based acquisition system in order to determine the amplitude and the phase of the sample magnetization as a function of the frequency of the driving magnetic field, which is powered by a digital waveform generator. A specific acquisition strategy makes the response directly proportional to the sample susceptibility, taking advantage of the differential nature of the coil assembly. A calibration method based on conductive samples is developed.Comment: 8 pages, 7 figures, 19 ref

Characterization of unwanted noise in realistic cavities

The problem of the description of absorption and scattering losses in high-Q cavities is studied. The considerations are based on quantum noise theories, hence the unwanted noise associated with scattering and absorption is taken into account by introduction of additional damping and noise terms in the quantum Langevin equations and input--output relations. Completeness conditions for the description of the cavity models obtained in this way are studied and corresponding replacement schemes are discussed.Comment: Contribution to XI International Conference on Quantum Optics, Minsk, Belarus, 26-31 May, 200

Determination of quantum-noise parameters of realistic cavities

A procedure is developed which allows one to measure all the parameters occurring in a complete model [A.A. Semenov et al., Phys. Rev. A 74, 033803 (2006); quant-ph/0603043] of realistic leaky cavities with unwanted noise. The method is based on the reflection of properly chosen test pulses by the cavity.Comment: 5 pages, 2 figure

Quantum-state input-output relations for absorbing cavities

The quantized electromagnetic field inside and outside an absorbing high-$Q$ cavity is studied, with special emphasis on the absorption losses in the coupling mirror and their influence on the outgoing field. Generalized operator input-output relations are derived, which are used to calculate the Wigner function of the outgoing field. To illustrate the theory, the preparation of the outgoing field in a Schr\"{o}dinger cat-like state is discussed.Comment: 12 pages, 5 eps figure

Intensity fluctuations in bimodal micropillar lasers enhanced by quantum-dot gain competition

We investigate correlations between orthogonally polarized cavity modes of a bimodal micropillar laser with a single layer of self-assembled quantum dots in the active region. While one emission mode of the microlaser demonstrates a characteristic s-shaped input-output curve, the output intensity of the second mode saturates and even decreases with increasing injection current above threshold. Measuring the photon auto-correlation function g^{(2)}(\tau) of the light emission confirms the onset of lasing in the first mode with g^{(2)}(0) approaching unity above threshold. In contrast, strong photon bunching associated with super-thermal values of g^{(2)}(0) is detected for the other mode for currents above threshold. This behavior is attributed to gain competition of the two modes induced by the common gain material, which is confirmed by photon crosscorrelation measurements revealing a clear anti-correlation between emission events of the two modes. The experimental studies are in excellent qualitative agreement with theoretical studies based on a microscopic semiconductor theory, which we extend to the case of two modes interacting with the common gain medium. Moreover, we treat the problem by an extended birth-death model for two interacting modes, which reveals, that the photon probability distribution of each mode has a double peak structure, indicating switching behavior of the modes for the pump rates around threshold.Comment: 11 pages, 5 figures, submitted to Phys. Rev.

Leaky cavities with unwanted noise

A phenomenological approach is developed that allows one to completely describe the effects of unwanted noise, such as the noise associated with absorption and scattering, in high-Q cavities. This noise is modeled by a block of beam splitters and an additional input-output port. The replacement schemes enable us to formulate appropriate quantum Langevin equations and input-output relations. It is demonstrated that unwanted noise renders it possible to combine a cavity input mode and the intracavity mode in a nonmonochromatic output mode. Possible applications to unbalanced and cascaded homodyning of the intracavity mode are discussed and the advantages of the latter method are shown.Comment: 13 pages, 7 figures; published versio

Mirrorless lasing: a theoretical perspective

Mirrorless lasing has been a topic of particular interest for about a decade due to promising new horizons for quantum science and applications. In this work, we review first-principles theory that describes this phenomenon, and discuss degenerate mirrorless lasing in a vapor of Rb atoms, the mechanisms of amplification of light generated in the medium with population inversion between magnetic sublevels within the $D_2$ line, and challenges associated with experimental realization

Photon emission by an atom in a lossy cavity

The dynamics of an initially excited two-level atom in a lossy cavity is studied by using the quantum trajectory method. Unwanted losses are included, such as photon absorption and scattering by the cavity mirrors and spontaneous emission of the atom. Based on the obtained analytical solutions, it is shown that the shape of the extracted spatiotemporal radiation mode sensitively depends on the atom-field interaction. In the case of a short-term atom-field interaction we show how different pulse shapes for the field extracted from the cavity can be controlled by the interaction time