26 research outputs found
Quantum Computing and Quantum Simulation with Group-II Atoms
Recent experimental progress in controlling neutral group-II atoms for
optical clocks, and in the production of degenerate gases with group-II atoms
has given rise to novel opportunities to address challenges in quantum
computing and quantum simulation. In these systems, it is possible to encode
qubits in nuclear spin states, which are decoupled from the electronic state in
the S ground state and the long-lived P metastable state on the
clock transition. This leads to quantum computing scenarios where qubits are
stored in long lived nuclear spin states, while electronic states can be
accessed independently, for cooling of the atoms, as well as manipulation and
readout of the qubits. The high nuclear spin in some fermionic isotopes also
offers opportunities for the encoding of multiple qubits on a single atom, as
well as providing an opportunity for studying many-body physics in systems with
a high spin symmetry. Here we review recent experimental and theoretical
progress in these areas, and summarise the advantages and challenges for
quantum computing and quantum simulation with group-II atoms.Comment: 11 pages, 7 figures, review for special issue of "Quantum Information
Processing" on "Quantum Information with Neutral Particles
Measuring absolute frequencies beyond the GPS limit via long-haul optical frequency dissemination
open15openClivati, Cecilia; Cappellini, Giacomo; Livi, Lorenzo F.; Poggiali, Francesco; de Cumis, Mario Siciliani; Mancini, Marco; Pagano, Guido; Frittelli, Matteo; Mura, Alberto; Costanzo, Giovanni A.; Levi, Filippo; Calonico, Davide; Fallani, Leonardo; Catani, Jacopo; Inguscio, MassimoClivati, Cecilia; Cappellini, Giacomo; Livi, Lorenzo F.; Poggiali, Francesco; de Cumis, Mario Siciliani; Mancini, Marco; Pagano, Guido; Frittelli, Matteo; Mura, Alberto; Costanzo, Giovanni A.; Levi, Filippo; Calonico, Davide; Fallani, Leonardo; Catani, Jacopo; Inguscio, Massim
Measuring absolute frequencies beyond the GPS limit via long-haul optical frequency dissemination
Global Positioning System (GPS) dissemination of frequency standards is ubiquitous at present, providing the most widespread time and frequency reference for the majority of industrial and research applications worldwide. On the other hand, the ultimate limits of the GPS presently curb further advances in high-precision, scientific and industrial applications relying on this dissemination scheme. Here, we demonstrate that these limits can be reliably overcome even in laboratories without a local atomic clock by replacing the GPS with a 642-km-long optical fiber link to a remote primary caesium frequency standard. Through this configuration we stably address the 1S0—3P0 clock transition in an ultracold gas of 173Yb, with a precision that exceeds the possibilities of a GPS-based measurement, dismissing the need for a local clock infrastructure to perform beyond-GPS high-precision tasks. We also report an improvement of two orders of magnitude in the
accuracy on the transition frequency reported in literature
Structure of Spin Correlations in High Temperature SU() Quantum Magnets
Quantum magnets with a large SU() symmetry are a promising playground for
the discovery of new forms of exotic quantum matter. Motivated by recent
experimental efforts to study SU() quantum magnetism in samples of ultracold
fermionic alkaline-earth-like atoms in optical lattices, we study here the
temperature dependence of spin correlations in the SU() Heisenberg spin
model in a wide range of temperatures. We uncover a sizeable regime in
temperature, starting at down to intermediate temperatures and for
all , in which the correlations have a common spatial structure on a
broad range of lattices, with the sign of the correlations alternating from one
Manhattan shell to the next, while the amplitude of the correlations is rapidly
decreasing with distance. Focussing on the one-dimensional chain and the
two-dimensional square and triangular lattice for certain , we discuss the
appearance of a disorder and a Lifshitz temperature, separating the
commensurate Manhattan high- regime from a low- incommensurate regime. We
observe that this temperature window is associated to an approximately
-independent entropy reduction from the entropy at infinite
temperature. Our results are based on high-temperature series arguments and as
well as large-scale numerical full diagonalization results of thermodynamic
quantities for SU() and SU() square lattice samples, corresponding to a
total Hilbert space of up to states.Comment: 14 pages, 8 figure
Quantum trajectories and open many-body quantum systems
The study of open quantum systems has become increasingly important in the
past years, as the ability to control quantum coherence on a single particle
level has been developed in a wide variety of physical systems. In quantum
optics, the study of open systems goes well beyond understanding the breakdown
of quantum coherence. There, the coupling to the environment is sufficiently
well understood that it can be manipulated to drive the system into desired
quantum states, or to project the system onto known states via feedback in
quantum measurements. Many mathematical frameworks have been developed to
describe such systems, which for atomic, molecular, and optical (AMO) systems
generally provide a very accurate description of the open quantum system on a
microscopic level. In recent years, AMO systems including cold atomic and
molecular gases and trapped ions have been applied heavily to the study of
many-body physics, and it has become important to extend previous understanding
of open system dynamics in single- and few-body systems to this many-body
context. A key formalism that has already proven very useful in this context is
the quantum trajectories technique. This was developed as a numerical tool for
studying dynamics in open quantum systems, and falls within a broader framework
of continuous measurement theory as a way to understand the dynamics of large
classes of open quantum systems. We review the progress that has been made in
studying open many-body systems in the AMO context, focussing on the
application of ideas from quantum optics, and on the implementation and
applications of quantum trajectories methods. Control over dissipative
processes promises many further tools to prepare interesting and important
states in strongly interacting systems, including the realisation of parameter
regimes in quantum simulators that are inaccessible via current techniques.Comment: 66 pages, 29 figures, review article submitted to Advances in Physics
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