2013-2012

Academic year 2012 - 2013

28 June Lincoln D. Carr, Colorado School of Mines (USA)

"Quantum many-body physics of ultracold molecules in optical lattices"

Ultracold polar heteronuclear molecules are the next wave of ultracold physics. At JILA the bialkali fermionic molecule KRb is already at quantum degeneracy in an optical lattice; many other molecular species are very close at Innsbruck, Heidelberg, Durham, MIT, and elsewhere. What is the natural many-body physics of such molecules in optical lattices? We explore this question and present a general molecular Hubbard Hamiltonian. Molecules represent a new kind of object for quantum many body physics because of their large number of internal degrees of freedom. We show how strong external magnetic and electric fields can be used to tune from one or two internal states to over a hundred. The interplay between external motion in the lattice and internal degrees of freedom leads to wonderful possibilities and presents many open questions. This talk will focus on a detailed description of KRb and other molecules, and development of the Molecular Hubbard Hamiltonian. We present an overview of experimental controls, much more versatile than for ultracold atoms. We conclude with three brief applications: phase diagrams in 1D via matrix-product state numerical methods, tunable quantum complexity, and quantum dephasing.

5 March J. Ricardo Arias-Gonzalez, IMDEA Nanociencia

"DNA polymerase: a Maxwell’s demon that replicates genetic information"

R. Landauer and C.H. Bennett showed that a logical copy can be carried out in the limit of no dissipation if the computation is performed sufficiently slowly. In biomolecular systems, the copy of genetic information is carried out by DNA polymerases, best known for their enzymatic activity. Structural and recent single-molecule manipulation assays have provided dynamic details of polymerase nanomachinery with insight into information processing. DNA polymerases have to translocate along a DNA template by burning chemical fuel but most importantly, they have to copy a DNA single strand so that the fidelity in the so-called polymerization reaction is crucial for the cell division. To do so, DNA polymerase actually works as both a Turing Machine and a Maxwell’s Demon: it is capable of successively reading one nucleotide at a time, identifying a complementary nucleotide in the environment and writing the information to the nascent replicated strand. Moreover, it is also capable of identifying errors by recognizing the secondary structure of the resulting double-stranded DNA.

We introduce a rigorous characterization of Shannon Information in biomolecular systems and apply it to DNA replication in the limit of no dissipation. It is known that replication occurs away from equilibrium and therefore the entropy here derived represents an upper bound for replication to take place. Likewise, this entropy sets a universal lower bound for the copying fidelity in replication.

6 February Anton Ramsak, University of Ljubljana & J. Stefan Institute, Slovenia

"Spin thermopower of a quantum dot"

Using analytical arguments and the numerical renormalization group method, we investigate the spin

thermopower of a quantum dot in a magnetic field. In the particle-hole-symmetric situation, the temperature difference applied across the dot drives a pure spin current without accompanying charge current. For temperatures and fields at or above the Kondo temperature, but of the same order of magnitude, the spin-Seebeck coefficient is large, of the order of kB/|e|. For several regimes, we provide simplified analytical expressions. In the Kondo regime, the dependence of the spin-Seebeck coefficient on the temperature and the magnetic field is explained in terms of the shift of the Kondo resonance due to the field and its broadening with the temperature and the field. We also consider the influence of breaking the particle-hole symmetry and show that a pure spin current can still be realized, provided a suitable electric voltage is applied across the dot.

3 December Iacopo Carusotto, INO-CNR BEC Center and Universita' di Trento

"A quantum optician’s perspective on analogue Hawking radiation in condensed-matter and optical systems"

After a brief presentation of the most promising condensed-matter systems that are presently investigated as analogue models of gravitational physics, I will discuss my understanding of Hawking radiation effects from a quantum optics perspective. The potential of this approach stems from its flexibility to take into account dispersive, Lorentz-violating features of real systems as well as from the well-established quantum optics tools that are available to study the very quantum features of the emission.