Squeezed light goes flexible

Since its first experimental demonstration,squeezed light has been the driving force to push forward the frontier of quantum optics[1].Recently,with the rapid d...     

Squeezed light from microstructured fibres: towards free-space quantum cryptography

Amplitude-squeezed pulsed light has been produced using a microstructured silica fibre. By spectrally filtering after the non-linear propagation in the fibre a squeezing value of -1.7 dB has been measured. A quantum key distribution scheme based on squeezed light from such microstructured fibres is proposed. Received: 9 July 2001 / Published online: 23 November 2001     

Squeezed states in resonance fluorescence of two interacting atoms

The possible existence of so-called “squeezed” states in two-atom resonance fluorescence is discussed in Lehmberg's master equation approach. It is shown that squeezing strongly depends on interatomic separations r₁₂. For large r₁₂ one of the quadrature components is squeezed, and as r₁₂ decreases its squeezing decreases in order to appear in the other quadrature component for certain value of r₁₂. For very small r₁₂ fluctuations in both components tend to zero.     

Entangled light pulses from single cold atoms

The coherent interaction between a laser-driven single trapped atom and an optical high-finesse resonator allows one to produce entangled multiphoton light pulses on demand. The mechanism is based on the mechanical effect of light. The degree of entanglement can be controlled through the parameters of the laser excitation. Experimental realization of the scheme is within reach of current technology. A variation of the technique allows for controlled generation of entangled subsequent pulses, with the atomic motion serving as intermediate memory of the quantum state.     

Coherent backscattering of light from saturated atoms

We survey recent progress achieved in understanding the impact of inelastic processes on coherent backscattering of light from cold atoms that are saturated by a powerful laser field.     

Squeezed states of light as self-similar structures

A new approach to investigating a broad class of dynamic states for a quantum oscillator is suggested. It is based on an invariant transformation of the equation to a new time determined by the quantum dispersion of the corresponding state. The squeezed states of a quantum system generated by the ground-state wave function are constructed. In coordinate representation, these states are described by a self-similar wave function localized near a classical trajectory. The statistics of the squeezed state of light is analyzed in the single-mode approximation. The parametric excitation of squeezed states for a quantum harmonic oscillator is considered.     

Spontaneous emission of light from atoms: the model

We investigate (non‐relativistic) atomic systems interacting with quantum electromagnetic field (QEF). The resulting model describes spontaneous emission of light from a two‐level atom surrounded by various initial states of the QEF. We assume that the quantum field interacts with the atom via the standard, minimal‐coupling Hamiltonian, with the A² term neglected. We also assume that there will appear at most single excitations (photons). By conducting the analysis on a general level we allow for an arbitrary initial state of the QEF (which can be for instance: the vacuum, the ground state in a cavity, or the squeezed state). We derive a Volterra‐type equation which governs the time evolution of the amplitude of the excited state. The two‐point function of the initial state of the QEF, integrated with a combination of atomic wavefunctions, forms the kernel of this equation.     

The polarization of light emitted from sputtered Mg atoms

The polarization fraction of light emitted from Mg atoms excited during bombardment of the Mg polycrystalline target by low-energy Ne⁺ ions has been measured. Taking into account the results, a possible mechanism of excitation of sputtered atoms is suggested.     

Muon transfer to light atoms

Several experiments performed by our group in recent years have put into evidence the complex structure of the time distributions of the muonic X-rays following transfer from muonic hydrogen isotopes to heavier elements. Simulations have shown that a substantial fraction of the µp atoms in the ground state have epithermal energies. Therefore, an energy dependence of the transfer rate seems a reasonable assumption for the explanation of the complex time structure.     

Time-resolved detection of atoms diffracted from a standing light wave

We present a time-resolved experimental observation of the diffraction of metastable helium atoms from a nearly resonant standing light wave. The application of a time-resolved detection technique and a pulsed source allows to resolve high diffraction orders, which are populated in the atom-light interaction. Furthermore, the rms momentum transfer from the light field on the atom as a function of the interaction time is investigated. Future applications of this technique may be the detailed investigation of the motion of atoms in standing light waves and the detection of correlations between spontaneously emitted photons and atoms.Dedicated to H. Walter on the occasion of his 60th birthday     

Scattering of atoms by light

This review discusses the latest theoretical and experimental achievements in the resonant light pressure acting on the translational motion of atoms. Alongside with the effects due to the spontaneous light pressure (atomic deflection, velocity bunching, cooling), various manifestations of the effects of induced light pressure are considered in detail. This paper provides the theory and experiments of atoms scattering by a standing light wave under the conditions of coherent and non-coherent interaction, diffraction and interference of atomic beams. The problems where atomic motion along two trajectories and Landau-Zener transitions between them are essential, are studied. The kinetic phenomena (scattering, cooling, channeling) due to the motion of the particles exposed to gradient force and also friction and diffusion caused by spontaneous emission are considered. The influence of the recoil effect under spontaneous emission of atoms on non-linear polarization phenomena is discussed.     

Stopping light via hot atoms

We prove that it is possible to freeze a light pulse (i.e., to bring it to a full stop) or even to make its group velocity negative in a coherently driven Doppler broadened atomic medium via electromagnetically induced transparency (EIT). This remarkable phenomenon of the ultraslow EIT polariton is based on the spatial dispersion of the refraction index n(omega,k), i.e., its wave number dependence, which is due to atomic motion and provides a negative contribution to the group velocity. This is related to, but qualitatively different from, the recently observed light slowing caused by large temporal (frequency) dispersion.     

Freezing light with cold atoms

The impact of disorder and localisation in electronic conduction was introduced more than half a century ago by Philip Anderson. In a much broader context of disorder-mediated wave dynamics it remains an important research area, and surprises abound. Meanwhile, research in ultracold atomic physics has led to phenomenally detailed elucidation of properties, including changes in phase, of quantum degenerate Bosonic and Fermionic gases. For example, beautiful experiments have recently demonstrated, in quasi one-dimensional systems, Anderson localisation of matter waves. In this brief essay, we describe and discuss research on wave localisation in the context of ultracold atomic physics, with a particular emphasis on light localisation in ultracold and high-density atomic gases. Essential ideas are reviewed, along with the current experimental status of the field, and promising avenues for future research are discussed.     

Artificial atoms can do more than atoms: deterministic single photon subtraction from arbitrary light fields

We study the interplay of photons interacting with an artificial atom in the presence of a controlled dephasing. Such artificial atoms consisting of several independent scatterers can exhibit remarkable properties superior to single atoms with a prominent example being a superatom based on Rydberg blockade. We demonstrate that the induced dephasing allows for the controlled absorption of a single photon from an arbitrary incoming probe field. This unique tool in photon-matter interaction opens a way for building novel quantum devices, and several potential applications such as a single photon transistor, high fidelity n-photon counters, or the creation of nonclassical states of light by photon subtraction are presented.     

Scattering of laser light from excited hydrogen atoms in a plasma

A method is described to achieve virtually full absorption of microwave power in an overdense plasma column of low collision frequency.