Quantum back-action of optical observations on Bose condensates

Impressive pictures of moving Bose-Einstein condensates have been taken using phase-contrast imaging M. R. Andrews et al., Science 273, 84 (1996). We calculate the quantum backaction of this measurement technique. We find that phase-contrast imaging is not a quantum nondemolition measurement of the atomic density. Instead, the condensate gets gradually depleted at a rate that is proportional to the light intensity and to the inverse cube of the optical wave length. The fewer atoms are condensed the higher is the required intensity to see a picture, and, consequently, the higher is the induced backaction. To describe the quantum physics of phase-contrast imaging we put forward a new approach to quantum-optical propagation. We develop an effective field theory of paraxial optics in a fully quantized atomic medium.Comment: 11 pages RevTex, 2 ps figures, revised. European Physical Journal D (in press

Reply to the ``Comment on `quantum backaction of optical observations on Bose-Einstein condensates' ''

In our paper we estimated the quantum backaction of dispersive imaging with off-resonant light on Bose-Einstein condensates. We have calculated the rates of the two processes involved, phase diffusion and depletion of the condensate. We compare here the depletion rate obtained within our model limitations to the Rayleigh scattering rate, both having the same physical origin: dispersive interaction of light with matter. We show that residual absorption sets indeed the limit of dispersive imaging.Comment: 1 page (Reply to comment

Theory of radiation trapping by the accelerating solitons in optical fibers

We present a theory describing trapping of the normally dispersive radiation by the Raman solitons in optical fibers. Frequency of the radiation component is continuously blue shifting, while the soliton is red shifting. Underlying physics of the trapping effect is in the existence of the inertial gravity-like force acting on light in the accelerating frame of reference. We present analytical calculations of the rate of the opposing frequency shifts of the soliton and trapped radiation and find it to be greater than the rate of the red shift of the bare Raman soliton. Our findings are essential for understanding of the continuous shift of the high frequency edge of the supercontinuum spectra generated in photonic crystal fibers towards higher frequencies.Comment: Several misprints in text and formulas corrected. 10 pages, 9 figures, submitted to Phys. Rev.

Slow light in moving media

We review the theory of light propagation in moving media with extremely low group velocity. We intend to clarify the most elementary features of monochromatic slow light in a moving medium and, whenever possible, to give an instructive simplified picture

Ultrahigh sensitivity of slow-light gyroscope

Slow light generated by Electromagnetically Induced Transparency is extremely susceptible with respect to Doppler detuning. Consequently, slow-light gyroscopes should have ultrahigh sensitivity

Quantized Roentgen Effect in Bose-Einstein Condensates

A classical dielectric moving in a charged capacitor can create a magnetic field (Roentgen effect). A quantum dielectric, however, will not produce a magnetization, except at vortices. The magnetic field outside the quantum dielectric appears as the field of quantized monopoles

Relativistic Effects of Light in Moving Media with Extremely Low Group Velocity

A moving dielectric medium acts as an effective gravitational field on light. One can use media with extremely low group velocities [Lene Vestergaard Hau et al., Nature 397, 594 (1999)] to create dielectric analogs of astronomical effects on Earth. In particular, a vortex flow imprints a long-ranging topological effect on incident light and can behave like an optical black hole.Comment: Physical Review Letters (accepted

Transition rates for q q bar -> pi pi pi in a chiral model

We investigate the nature of transition rates for the hadronization process of q q bar -> Pi Pi Pi as opposed to the transition rates for q q bar -> Pi Pi, within the Nambu--Jona-Lasinio model that has manifest chiral symmetry. Feynman diagrams appropriate to this process can be classified according to the expansion in the inverse number of colors 1/N_c. Two of these types of graphs are seen to be either 's-like' or 't-like' in nature. A further graph that contains both s-like and t-like elements, and which is denoted as st-like, is also present. To describe such a process with two incoming and three outgoing particles, it is necessary to extend the number of Mandelstam invariants. It is convenient to introduce seven such variables, of which only five are independent. The cross section for two incoming particles to three outgoing particles is then reexpressed in integral form in terms of these invariants. As a function of sqrt s, the final expression is reduced to an integral over the four remaining invariants. The limits of integration, which are now non-trivial, are also discussed. The transition rate for the explicit case of u u bar -> Pi^+ Pi^- Pi^0, is evaluated numerically, assuming non-chiral pions, m_Pi = 135MeV. The rate for three pion production is found to be of the same order of magnitude as for two pion production, making this a non-negligible contribution to hadronization.Comment: 33 LaTex pages plus 1 postscript file containing 12 figures. To be published in Nuclear Physics

Optics of Nonuniformly Moving Media

A moving dielectric appears to light as an effective gravitational field. At low flow velocities the dielectric acts on light in the same way as a magnetic field acts on a charged matter wave. We develop in detail the geometrical optics of moving dispersionless media. We derive a Hamiltonian and a Lagrangian to describe ray propagation. We elucidate how the gravitational and the magnetic model of light propagation are related to each other. Finally, we study light propagation around a vortex flow. The vortex shows an optical Aharonov--Bohm effect at large distances from the core, and, at shorter ranges, the vortex may resemble an optical black hole.Comment: Physical Review A (submitted

π\pi-KK scattering lengths at finite temperature in the Nambu--Jona-Lasinio model

The transition amplitude for $\pi K$ scattering is evaluated within the SU(3) Nambu--Jona-Lasinio model. Ordering terms according to the expansion in $1/N_c$ leads to a box-like diagram, $t$ channel diagrams that admit scalar isoscalar $(\sigma,\sigma')$ exchanges, and a $u$ channel exchange of a scalar isodoublet $\sigma_K$ that has quantum numbers corresponding to the $K_0^*(1430)$. Both the Pauli-Villars and O(3) regularization procedures are used to evaluate the T=0 values of the $l=0$ scattering lengths $a_0^{3/2}$ and $a_0^{1/2}$. The finite temperature dependence is studied. We find that the variation in the $t$ channel in the calculation of $a_0^{3/2}$ leads to a change in $a_0^{3/2}$ of a factor of about two over the temperature range of T=150 MeV