<html><body><div id="zimbraEditorContainer" style="font-family: georgia,serif; font-size: 11pt; color: #000000" class="6"><div><style></style><style></style><style></style><style></style><style></style><style></style><style></style><style></style><style></style><style></style><style></style><style></style><style></style><style></style><style></style><style></style><style></style><style></style><style></style><style></style><style></style><style></style><style></style></div><div data-marker="__QUOTED_TEXT__"><div style="font-family:'georgia' , serif;font-size:11pt;color:#000000"><div></div><div></div><div><div style="font-family:'georgia' , serif;font-size:11pt;color:#000000"><div style="color:#000000;font-family:'georgia' , serif;font-size:11pt"><br></div><div><div><div style="text-align:left"><div style="color:#000000;font-family:'times new roman' , 'new york' , 'times' , serif;font-size:12pt;text-align:center"><strong><b><span lang="HR" style="color:black;font-size:16pt"><img src="cid:fb559ca8379da07816ebeb024a88bd13dae62179@zimbra" data-mce-src="cid:fb559ca8379da07816ebeb024a88bd13dae62179@zimbra"></span></b></strong></div><div style="color:#000000;font-family:'times new roman' , 'new york' , 'times' , serif;font-size:12pt;text-align:center"><p align="center" style="margin:0px;text-align:center"><b><span lang="EN-GB" style="color:#5f5f5f;font-family:'century gothic' , sans-serif">Institut za fiziku, Bijenička cesta 46,</span></b></p><p align="center" style="margin:0px;text-align:center"><b><span lang="EN-GB" style="color:#5f5f5f;font-family:'century gothic' , sans-serif">predavaonica u zgradi Mladen Paić</span></b></p><p align="center" style="margin:0px;text-align:center"><b><span lang="EN-GB" style="color:#5f5f5f;font-family:'century gothic' , sans-serif"></span></b><br></p><p align="center" style="margin:0px;text-align:center"><br></p><strong><b><span lang="EN-GB" style="color:#993300;font-family:'century gothic' , sans-serif;font-size:14pt">Srijeda, 24. srpnja 2019., u 15:00 sati</span></b></strong></div><div style="text-align:center"><p class="MsoNormal" style="color:#000000;font-family:'times new roman' , 'new york' , 'times' , serif;font-size:12pt;margin:0px"><br></p><h2 class="MsoNormal" align="center" style="color:#000000;font-family:'times new roman' , 'new york' , 'times' , serif;font-size:12pt;text-align:center;margin:0px"> </h2><p class="PreformattedText" style="margin:0px"><span style="font-size:18pt;font-family:'georgia' , serif;color:rgb( 0 , 0 , 255 )"><strong>Self-ordering and quantum optimization of cold atoms in a multi-mode cavity</strong></span></p><div style="color:#000000;font-family:'times new roman' , 'new york' , 'times' , serif;font-size:12pt"><strong><span style="color:#0000ff"><span style="font-size:16pt;font-family:'georgia' , serif"></span></span></strong><br></div><div><span style="color:#ff0000"><span style="font-size:21.3333px"><b> Valentin Torggler, Institute for theoretical physics, Innsbruck, Austrija</b></span></span></div></div></div></div><div style="color:#000000;font-family:'arial' , 'helvetica' , sans-serif;font-size:12pt;text-align:left"><b><b><span lang="EN-GB" style="font-family:'century gothic' , sans-serif;font-size:12pt"><b><span lang="EN-GB" style="font-family:'century gothic' , sans-serif;font-size:11pt"> </span></b></span></b></b><h3 class="MsoNormal" style="margin:0px"><br></h3><h3 class="MsoBodyText" style="margin:0px"> <span style="font-size:16pt;font-family:'comic sans ms' , 'comic sans' , sans-serif"><span style="color:black">A cold dilute atomic gas collectively scatters light into an optical resonator when illuminated by laser light from the side. This leads to a complex coupled atom-field dynamics, including all-to-all atom-atom interactions and cavity cooling. For a sufficiently high laser power, the atoms’ steady state undergoes a phase transition from homogeneous to crystalline order. When applying several laser beams scattered into cavity modes with distinct spatial structure, a multitude of meta-stable ordered patterns emerges. As opposed to the single-mode case, attaining the optimally scattering state is not trivial anymore due to the existence of local minima in the energy landscape. By numerical simulations of the semi-classical dynamics we show that the stationary state strongly depends on the laser intensity ramp speed and the initial temperature.</span> </span><br></h3><div><span style="font-size:16pt;font-family:'comic sans ms' , 'comic sans' , sans-serif"></span><br></div><div><span style="font-size:16pt;font-family:'comic sans ms' , 'comic sans' , sans-serif"> <strong><span style="color:black">The task of solving hard optimization problems can be recast into the minimization of a multivariate cost function. We show that the cost function can be emulated by the cavity-mediated all-to-all interactions, rendering the system described above a potential platform for solving optimization problems. In the quantum realm, ultra-cold bosons in optical lattices in a cavity can be used to implement a form of quantum annealing. In this vein, we propose a special purpose quantum simulator aimed at solving the N-queens problem. Variations of the N-queens problem are NP-complete and classically hard instances exist for relatively small atom numbers. Our implementation has no overhead from the embedding allowing to directly probe for a possible quantum speed-up in near term devices.</span></strong></span></div></div><div style="color:#000000;font-family:'arial' , 'helvetica' , sans-serif;font-size:12pt;text-align:left"><br></div><div style="color:#000000;font-family:'arial' , 'helvetica' , sans-serif;font-size:12pt;text-align:left"><span style="font-size:12pt"><b><span lang="EN-GB" style="font-family:'century gothic' , sans-serif"><b><span lang="EN-GB" style="font-family:'century gothic' , sans-serif">Voditelji seminara IF-a: <a href="mailto:hrvoje@ifs.hr" rel="nofollow%20noopener%20noreferrer nofollow noopener noreferrer" target="_blank">Hrvoje Skenderović</a> i <a href="mailto:damirs@ifs.hr" rel="nofollow%20noopener%20noreferrer nofollow noopener noreferrer" target="_blank">Damir Starešinić<br></a></span></b></span></b></span></div></div></div><br></div></div><br></div></div></body></html>