Quantum network of neutral atom clocks

We propose a protocol for creating a fully entangled GHZ-type state of neutral atoms in spatially separated optical atomic clocks. In our scheme, local operations make use of the strong dipole-dipole interaction between Rydberg excitations, which give rise to fast and reliable quantum operations involving all atoms in the ensemble. The necessary entanglement between distant ensembles is mediated by single-photon quantum channels and collectively enhanced light-matter couplings. These techniques can be used to create the recently proposed quantum clock network based on neutral atom optical clocks. We specifically analyze a possible realization of this scheme using neutral Yb ensembles.Comment: 13 pages, 11 figure

Razvoj lokalnih kapaciteta za sudjelovanje u upravljanju zaštićenim područjem Nacionalnog parka Tara

In this study the focus is on the role of local communities in the management of protected areas with the expectation that without the coo peration and assistance of local communities achieving biodiversity conser vation in places where the land and resources are fundamental to supporting people’s livelihoods will be less successful than if the local people actively support this goal. Management capacity in protected areas depends upon the system of go vernance, the level of resources and local community support. The key que stion of interest at the global level are whether the responsible authorities have the capacity to manage their protected areas effectively, and whether de sired outcomes are achieved on the ground. Measuring these dimensions is contextual; what is effective in one country or locale may be inappropriate in another. Thus, assessing management capacity is context specific. The potential declaration of Tara National Park located in Serbia as a Biosphere Reserve necessitated research to characterize the institutional con text, the social and demographic situation of the communities within the Park boundaries. There is a growing recognition that the sustainable management of protected areas ultimately depends on the cooperation and support of the local people. In order to achieve sustainable conservation, state legislators and environmental planners should involve local people in the management of protected areas and need to identify and promote social processes that enable local communities to conserve and enhance biodiversity as a part of their live lihood system. Drawing upon research in Tara National Park, this paper analyzes the po tential capacity of people living within Tara National Park to effectively parti cipate in the management of the protected area by incorporating activities that promote biodiversity within their everyday livelihood strategies. The re sults demonstrate that sustaining or providing alternative livelihood strate gies is necessary in order to halt the exploitation of protected areas by local people striving to survive.Ovdje predstavljeno istraživanje usmjereno je na ulogu lokalne zajednice u upravljanju zaštićenim područjima, s osnovnom pretpostavkom da će bez suradnje i sudjelovanja lokalne zajednice u očuvanju biološke raznoliko sti na području gdje su zemlja i resursi temeljni oslonci za život ljudi, biti manje uspješno ako lokalno stanovništvo aktivno ne podupire zadane ciljeve očuvanja. Upravljački kapaciteti zaštićenih područja ovise o općem sustavu uprav ljanja, stanju samog resursa i podršci lokalne zajednice. Stoga se postavlja ključno pitanje od općeg interesa: imaju li odgovorne strukture kapaciteta za učinkovito upravljanje zaštićenim područjima, te da li se željeni rezultati po stižu na terenu. Mjerenje navedenih dimenzija upravljanja kontekstualnog je karaktera, jer ono što je učinkovito u jednoj zemlji ili lokalno, može biti sa svim neprihvatljivo u drugoj. Zbog toga se procjena upravljačkih kapaciteta po svome karakteru smatra kontekstualnom, odnosno bavi se prvo objašnja vanjem odnosa, a onda institucionalnih i strukturnih okvira. Prijedlog proglašenja Nacionalnog parka Tara Rezervatom Biosfere uka zao je na važnost istraživanja koje bi opisalo institucionalni okvir, socio-de mografsku situaciju u naseljima unutar granica Parka. Jasno je raspoznata ovisnost potrajnog gospodarenja zaštićenim prostorima o podršci lokalnog stanovništva. U cilju postizanja očuvanja biološke raznolikosti nacionalni za konodavac i okolišni planeri trebaju uključiti lokalno stanovništvo u upravlja nje zaštićenim prostorima, te utvrditi i razvijati socijalne procese kako bi omogućili lokalnim zajednicama očuvanje i unapređenje biološke raznolikosti kao dio njihovog životnog okruženja. Metoda istraživanja je kvalitativna, što proizlazi iz prirode prikupljenih po dataka i primijenjenih metoda analize i interpretacije. Primijenjena je studija slučaja (Case study) u sklopu koje su podaci prikupljeni tijekom 2004. godine, kada su obavljena 102 intervijua s lokalnim stanovništvom. Istraživanjem su obuhvaćena dva sela smještena na području Nacionalnog parka Tara: Rastište (67 intervjua) i Jagoštica (37). Oba sela su zbog slabe razvijenosti mreže puto ­va prometno izolirana, te stoga izrazito ovisna o lokalnim prirodnim resursima kao i gospodarskim i upravljačkim aktivnostima samoga Parka. Intervjui s lo­kalnim stanovništvom obuhvaćali su: demografske informacije o kućanstvu; stavove prema životu na selu; percepciju prirode i krajobraza; odnos sa Upra vom Parka; i pitanja vezana uz strategije kućanstva kroz povijest, sadašnje i njihova očekivanja za budućnost (Tomićević 2005). Sama pitanja bila su otvo rena, s ponuđenim odgovorima te mogućnošću davanja više odgovora. Svi in tervjui obavljeni su u samim kućanstvima, što je omogućavalo ispitanicima da i primjerom objasne kako žive i rade te na koje načine utječu na krajobraz. Tako đer su mogli lako objasniti kako institucionalne promjene utječu na njihovu volju za suradnjom s Upravom Parka, kao i njihova očekivanja u budućnosti. Intervjui su u potpunosti prepisani, što je omogućilo njihovu obradu i analizu korištenjem SPSS (Statističkog probrama za socijalna istraživanja) programa. Dodatno su obavljeni i problemski orijentirani intervjui sa stručnjacima i donositeljima odluka u Parku, nadležnim institucijama i znanstvenim organi za cijama (obavljeno je 5 intervjua) kako bi se dobio uvid u način sagledavanja problema s razine donositelja odluka. To znači da ispitanici nisu predstavljali sebe kao osobu, već su pružali stručno mišljenje u svom institucionalnom i/ili organizacijskom kontekstu (Meuser i Nagel 1991). Korištena pitanja bila su otvorena i polu strukturirana, koncentrirajući se na ključne probleme vezane uz sudjelovanje lokalnog stanovništva u upravaljanju Parkom, uključujući konflikte između lokalnog stanovništva i korištenja prirodnih resursa. Prikup ljena su i razmišljanja stručnjaka o budućnosti Parka. Svi prikupljeni podaci uneseni su u bazu te analizirani korištenjem SPSS programa, posebno namijenjenom za analizu kvalitativnih podataka. Tijekom analize i interpretacije dobivenih rezultata korištena je metoda triangulacije (unakrsnog potvrđivanja) gdje se jedna grupa podataka analizira u odnosu na drugu grupu, čime se omogućava razumijevanje prošlih, postojećih i budućih postupaka. Ova metoda posebno se pokazala korisnom u razumijevanju strate gija primijenjenih u lokalnim kućanstvima. Također je analizom drugih priku pljenih dokumenata i pravnih akata, dobiven uvid u odnose između lokalnog stanovništva i uprave Parka te karakteristike šireg zemljopisnog i instituciona lnog okruženja koje utječu na kapacitete zaštite prirode unutar Nacionalnog parka Tara. Ovim istraživanjem analizirani su mogućnosti razvoja kapaciteta stano vništva, koje živi u granicama samog Parka, te učinkovitog sudjelovanja u upravljanju zaštićenim područjem, kroz uključivanje u aktivnosti unapređenja biološke raznolikosti u svoje svakodnevne životne odluke. Polučeni rezultati ukazuju na neophodnost očuvanja i osiguravanja alternativnih životnih stra te gija, s ciljem zaustavljanja iskorištavanja zaštićenih područja od strane lo kalnog stanovništva, koje se istovremeno bori za očuvanje i unapređenje vla stitih životnih uvjeta. Analiza stručnih intervjua ukazala je na nedostatak općih strateških doku menata, koji bi regulirali zaštitu biološke raznolikosti i upravljanje zaštićenim prostorima u Srbiji, posebice onim od međunarodnog značenja

Collective Charge Excitations below the Metal-to-Insulator Transition in BaVS3

The charge response in the barium vanadium sulfide (BaVS3) single crystals is characterized by dc resistivity and low frequency dielectric spectroscopy. A broad relaxation mode in MHz range with huge dielectric constant ~= 10^6 emerges at the metal-to-insulator phase transition TMI ~= 67 K, weakens with lowering temperature and eventually levels off below the magnetic transition Tchi ~= 30 K. The mean relaxation time is thermally activated in a manner similar to the dc resistivity. These features are interpreted as signatures of the collective charge excitations characteristic for the orbital ordering that gradually develops below TMI and stabilizes at long-range scale below Tchi.Comment: 6 pages, 3 figures, submitted to PR

Optomechanical Cavity Cooling of an Atomic Ensemble

We demonstrate cavity sideband cooling of a single collective motional mode of an atomic ensemble down to a mean phonon occupation number of 2.0(-0.3/+0.9). Both this minimum occupation number and the observed cooling rate are in good agreement with an optomechanical model. The cooling rate constant is proportional to the total photon scattering rate by the ensemble, demonstrating the cooperative character of the light-emission-induced cooling process. We deduce fundamental limits to cavity-cooling either the collective mode or, sympathetically, the single-atom degrees of freedom.Comment: Paper with supplemental material: 4+6 pages, 4 figures. Minor revisions of text. Supplemental material shortened by removal of supplementary figur

Ultracold molecules: vehicles to scalable quantum information processing

We describe a novel scheme to implement scalable quantum information processing using Li-Cs molecular state to entangle $^{6}$Li and $^{133}$Cs ultracold atoms held in independent optical lattices. The $^{6}$Li atoms will act as quantum bits to store information, and $^{133}$Cs atoms will serve as messenger bits that aid in quantum gate operations and mediate entanglement between distant qubit atoms. Each atomic species is held in a separate optical lattice and the atoms can be overlapped by translating the lattices with respect to each other. When the messenger and qubit atoms are overlapped, targeted single spin operations and entangling operations can be performed by coupling the atomic states to a molecular state with radio-frequency pulses. By controlling the frequency and duration of the radio-frequency pulses, entanglement can either be created or swapped between a qubit messenger pair. We estimate operation fidelities for entangling two distant qubits and discuss scalability of this scheme and constraints on the optical lattice lasers

Vacuum-stimulated cooling of single atoms in three dimensions

Taming quantum dynamical processes is the key to novel applications of quantum physics, e.g. in quantum information science. The control of light-matter interactions at the single-atom and single-photon level can be achieved in cavity quantum electrodynamics, in particular in the regime of strong coupling where atom and cavity form a single entity. In the optical domain, this requires permanent trapping and cooling of an atom in a micro-cavity. We have now realized three-dimensional cavity cooling and trapping for an orthogonal arrangement of cooling laser, trap laser and cavity vacuum. This leads to average single-atom trapping times exceeding 15 seconds, unprecedented for a strongly coupled atom under permanent observation.Comment: 4 pages, 4 figure

The Croatian Health Survey – SF-36: I. General Quality of Life Assessment

The objective of the Croatian Health Survey was the assessment of population health related quality of life in the transitional enviroment of Croatia. Health status measures incorporate dimensions such as physical, psychological, and social functioning, role performance and perception of wellbeing. In order to assess health status, »The medical outcome study 36-item short-form health survey (SF-36) model« was used. A total sample of 5048 inhabitants (1983 males and 3065 females), 18 years and over, represents approximately 1‰ of the general population of Croatia. Mean scores were as follows: physical functioning (PF) 69.94, role-physical (RP)63.01, bodily pain (BP) 64.51, general health (GH) 53.40, vitality (VT) 51.85, social functioning (SF) 72.96, role-emotional (RE) 72.42, mental health (MH) 61.71 and health transition (HT) 44.79. Results of the SF-36 health survey in Croatia are very much like the results in other European countries with indication that general quality of life is lower in Croatia

Bose-Einstein condensation in quasi2D trapped gases

We discuss BEC in (quasi)2D trapped gases and find that well below the transition temperature $T_c$ the equilibrium state is a true condensate, whereas at intermediate temperatures $T<T_c$ one has a quasicondensate (condensate with fluctuating phase). The mean-field interaction in a quasi2D gas is sensitive to the frequency $\omega_0$ of the (tight) confinement in the "frozen" direction, and one can switch the sign of the interaction by changing $\omega_0$. Variation of $\omega_0$ can also reduce the rates of inelastic processes, which opens prospects for tunable BEC in trapped quasi2D gases.Comment: 4 revtex pages, 1 figure, text is revised, figure improve