Fermi condensates for dynamic imaging of electro-magnetic fields

Ultracold gases provide micrometer size atomic samples whose sensitivity to external fields may be exploited in sensor applications. Bose-Einstein condensates of atomic gases have been demonstrated to perform excellently as magnetic field sensors \cite{Wildermuth2005a} in atom chip \cite{Folman2002a,Fortagh2007a} experiments. As such, they offer a combination of resolution and sensitivity presently unattainable by other methods \cite{Wildermuth2006a}. Here we propose that condensates of Fermionic atoms can be used for non-invasive sensing of time-dependent and static magnetic and electric fields, by utilizing the tunable energy gap in the excitation spectrum as a frequency filter. Perturbations of the gas by the field create both collective excitations and quasiparticles. Excitation of quasiparticles requires the frequency of the perturbation to exceed the energy gap. Thus, by tuning the gap, the frequencies of the field may be selectively monitored from the amount of quasiparticles which is measurable for instance by RF-spectroscopy. We analyse the proposed method by calculating the density-density susceptibility, i.e. the dynamic structure factor, of the gas. We discuss the sensitivity and spatial resolution of the method which may, with advanced techniques for quasiparticle observation \cite{Schirotzek2008a}, be in the half a micron scale.Comment: 10 pages, 4 figure

Compliance in own-check systems poses challenges in small-scale slaughterhouses

Small-scale slaughterhouses (SHs) face many challenges, not least due to the requirements of food safety legislation. Food business operators' (FBOs') own-check system is very important for food safety, but its proper implementation can be quite difficult and laborious for small-scale SHs. In the European Union, the importance not only of food safety but also facilitation of local food production, including small-scale slaughtering, is highlighted. The aim of our study was to assess compliance with legislation of own-check systems, including six own-check programmes and HACCP, in small-scale SHs. The FBOs' opinions of the implementation of own-check systems were also sought to elucidate possible obstacles in implementation. Our results showed that the best compliance in own-check programmes was achieved in temperature of storage rooms and traceability. FBOs also evaluated these programmes as necessary. However, FBOs' perceived necessity of own-check programmes did not always lead to compliance, as was the case with labelling and HACCP. Instead, in HACCP laboriousness and compliance showed a negative correlation (p <0.05). In addition to laboriousness, costs of own-check programmes, specifically concerning microbiological sampling requirements, appeared to influence compliance, with many of the small-scale SHs poorly following sampling requirements. FBOs also noted the high costs of the non-edible by-product programme. Moreover, the results show that official veterinarians' assessment of compliance was significantly higher than that of the researcher, which warrants further investigation. This study reveals that many small-scale SHs in Finland struggle with food safety requirements. Amendments of some of the requirements to ease the burden of FBOs are proposed. HACCP in particular is suggested to be simplified. In addition, ways to improve food safety and official control in small-scale SHs are discussed.Peer reviewe

Noise correlations of the ultra-cold Fermi gas in an optical lattice

In this paper we study the density noise correlations of the two component Fermi gas in optical lattices. Three different type of phases, the BCS-state (Bardeen, Cooper, and Schieffer), the FFLO-state (Fulde, Ferrel, Larkin, and Ovchinnikov), and BP (breach pair) state, are considered. We show how these states differ in their noise correlations. The noise correlations are calculated not only at zero temperature, but also at non-zero temperatures paying particular attention to how much the finite temperature effects might complicate the detection of different phases. Since one-dimensional systems have been shown to be very promising candidates to observe FFLO states, we apply our results also to the computation of correlation signals in a one-dimensional lattice. We find that the density noise correlations reveal important information about the structure of the underlying order parameter as well as about the quasiparticle dispersions.Comment: 25 pages, 11 figures. Some figures are updated and text has been modifie

Finite temperature phase diagram of a polarized Fermi gas in an optical lattice

We present phase diagrams for a polarized Fermi gas in an optical lattice as a function of temperature, polarization, and lattice filling factor. We consider the Fulde-Ferrel-Larkin-Ovchinnikov (FFLO), Sarma or breached pair (BP), and BCS phases, and the normal state and phase separation. We show that the FFLO phase appears in a considerable portion of the phase diagram. The diagrams have two critical points of different nature. We show how various phases leave clear signatures to momentum distributions of the atoms which can be observed after time of flight expansion.Comment: Journal versio

Multi-mode lasing in supercell plasmonic nanoparticle arrays

Multicolour light sources can be used in applications such as lighting and multiplexing signals. In photonic and plasmonic systems, one way to achieve multicolour light is via multi-mode lasing. To achieve this, plasmonic nanoparticle arrays are typically arranged in superlattices that lead to multiple dispersions of the single arrays coupled via the superlattice Bragg modes. Here, we show an alternative way to enable multi-mode lasing in plasmonic nanoparticle arrays. We design a supercell in a square lattice by leaving part of the lattice sites empty. This results in multiple dispersive branches caused by the supercell period and hence creates additional band edges that can support lasing. We experimentally demonstrate multi-mode lasing in such a supercell array. Furthermore, we identify the lasing modes by calculating the dispersion by combining the structure factor of the array design with an empty lattice approximation. We conclude that the lasing modes are the 74th $\Gamma$- and 106th $X$-point of the supercell. By tuning the square lattice period with respect to the gain emission we can control the modes that lase. Finally, we show that the lasing modes exhibit a combination of transverse electric and transverse magnetic mode characteristics in polarization resolved measurements

Experimentally realizable quantum comparison of coherent states and its applications

When comparing quantum states to each other, it is possible to obtain an unambiguous answer, indicating that the states are definitely different, already after a single measurement. In this paper we investigate comparison of coherent states, which is the simplest example of quantum state comparison for continuous variables. The method we present has a high success probability, and is experimentally feasible to realize as the only required components are beam splitters and photon detectors. An easily realizable method for quantum state comparison could be important for real applications. As examples of such applications we present a "lock and key" scheme and a simple scheme for quantum public key distribution.Comment: 14 pages, 5 figures, version one submitted to PRA. Version two is the final accepted versio

Prerequisites of inspection conditions for uniform post-mortem inspection in broiler chicken slaughterhouses in Finland

Meat inspection of broiler chickens (broiler) in the European Union is regulated by common legislation to secure meat safety. However, the legislation is general in nature and proper post-mortem inspection (PMI) of every carcass and visceral organs of broilers is challenging in slaughterhouses (SHs) with a high slaughter line speed. The aim of this study was to investigate the on-site organization and possible differences of the PMI in four Finnish SHs, which slaughter over 99% of broilers in Finland. Our results show that the meat inspector's available inspection time per broiler in the PMI varied between 0.28 and 0.90 s, with the shortest available inspection time in the SH with the highest slaughter line speed and the longest available inspection time in the SH with the slowest line speed. We observed that only part of the total inspection time per broiler could be used for true PMI in most (3/4) SHs, as the meat inspectors also performed other tasks during the PMI. We observed deficiencies in the visual inspection of broiler carcasses; in particular, the proper inspection of all or most of the body cavities was impossible in all SHs during the PMI. Some deficiencies in facilities (e.g. in recording system) were observed. Moreover, lighting properties varied between the SHs and a significant difference between illumination conditions at the first inspection stations in the SHs was observed. This study considered the prerequisites for proper PMI and revealed that the PMI of broilers was not completely uniform in Finland. The results emphasize the need for more precise guidelines and recommendations, especially for inspection time and lighting at inspection stations.Peer reviewe

Guiding and reflecting light by boundary material

We study effects of finite height and surrounding material on photonic crystal slabs of one- and two-dimensional photonic crystals with a pseudo-spectral method and finite difference time domain simulation methods. The band gap is shown to be strongly modified by the boundary material. As an application we suggest reflection and guiding of light by patterning the material on top/below the slab.Comment: 12 pages, 7 figure

Vacuum Rabi splitting and strong coupling dynamics for surface plasmon polaritons and Rhodamine 6G molecules

We report on strong coupling between surface plasmon polaritons (SPP) and Rhodamine 6G (R6G) molecules, with double vacuum Rabi splitting energies up to 230 and 110 meV. In addition, we demonstrate the emission of all three energy branches of the strongly coupled SPP-exciton hybrid system, revealing features of system dynamics that are not visible in conventional reflectometry. Finally, in analogy to tunable-Q microcavities, we show that the Rabi splitting can be controlled by adjusting the interaction time between waveguided SPPs and R6G deposited on top of the waveguide. The interaction time can be controlled with sub-fs precision by adjusting the length of the R6G area with standard lithography methods.Comment: 4 pages, 4 figure

Quantum description of light pulse scattering on a single atom in waveguides

We present a time dependent quantum calculation of the scattering of a few-photon pulse on a single atom. The photon wave packet is assumed to propagate in a transversely strongly confined geometry, which ensures strong atom-light coupling and allows a quasi 1D treatment. The amplitude and phase of the transmitted, reflected and transversely scattered part of the wave packet strongly depend on the pulse length (bandwidth) and energy. For a transverse mode size of the order of $\lambda^2$, we find nonlinear behavior for a few photons already, or even for a single photon. In a second step we study the collision of two such wave packets at the atomic site and find striking differences between Fock state and coherent state wave packets of the same photon number.Comment: to appear in Phys. Rev.