Person:

Lukin, Mikhail

We suggest a new method for quantum optical control with nanoscale resolution. Our method allows for coherent far-field manipulation of individual quantum systems with spatial selectivity that is not limited by the wavelength of radiation and can, in principle, approach a few nanometers. The selectivity is enabled by the nonlinear atomic response, under the conditions of electromagnetically induced transparency, to a control beam with intensity vanishing at a certain location. Practical performance of this technique and its potential applications to quantum information science with cold atoms, ions, and solid-state qubits are discussed.

We present a procedure that makes use of group theory to analyze and predict the main properties of the negatively charged nitrogen-vacancy (NV) center in diamond. We focus on the relatively low temperature limit where both the spin–spin and spin–orbit effects are important to consider. We demonstrate that group theory may be used to clarify several aspects of the NV structure, such as ordering of the singlets in the ((e^2)) electronic configuration and the spin–spin and spin–orbit interactions in the ((ae)) electronic configuration. We also discuss how the optical selection rules and the response of the center to electric field can be used for spin–photon entanglement schemes. Our general formalism is applicable to a broad class of local defects in solids. The present results have important implications for applications in quantum information science and nanomagnetometry.

We calculate the rate of creation of double occupancies in a 3D Fermionic Mott insulator near half-filling by modulation of optical lattice potential. At high temperatures, incoherent holes lead to a broad response peaked at the Hubbard repulsion (U). At low temperatures, antiferromagnetic order leads to a coherent peak for the hole along with broad features representing spin wave shake-off processes. This is manifested in the doublon creation rate as a sharp absorption edge and oscillations as a function of modulating frequency. Thus, modulation spectroscopy can be used as a probe of antiferromagnetic order and nature of quasiparticle excitations in the system.

(d)-wave Cooper pairs are believed to be the key for understanding the phenomenon of high-temperature superconductivity in cuprates. These superconductors are an example of the emergence of strong pairing in systems with purely repulsive interactions, similar to superfluid helium 3 and the newly discovered iron oxypnictides. Despite intense studies, there is currently no consensus as to what causes the formation of (d)-wave Cooper pairs in these materials. Here we propose a novel experimental scheme in which recently demonstrated methods for realizing optical lattices and superlattices are combined to create and to detect, in a controlled way, ultracold-atom (d)-wave Cooper pairs. Our scheme starts from arrays of isolated plaquettes which incorporate the required (d)-wave correlations on a short length scale. By tuning the parameters of the potentials, these plaquettes can be coupled to achieve long-range (d)-wave superfluid correlations, finally arriving at the generic Hubbard model.