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- Dissipation caused by nonhomogeneous bosonic finite chain environments (implementable in, e.g., segmented ion traps) is investigated through an exact diagonalization approach, avoiding common approximations used to describe open systems. Different spectral densities, including band gaps, can be engineered to separately assess different factors leading to memory effects, namely, the environment's size, temperature, proximity of the cutoff frequency, the spectral density's shape (sub-Ohmic, Ohmic, super-Ohmic), and the strength of its coupling to the system. Non-Markovianity is quantified with two recently introduced measures related to information backflow and nondivisibility of the system dynamical map. By sweeping the bath spectrum via tuning of the system frequency we show strongest memory effects at band-gap edges and provide an interpretation based on energy flow between system and environment. A system weakly coupled to a stiff chain ensures a Markovian dynamics, while the size of the environment as well as the local density of modes are not substantial factors. We show an opposite effect when increasing the temperature inside or outside the spectral band gap. Further, non-Markovianity arises for larger (negative and positive) powers of algebraic spectral densities, being the Ohmic case not always the most Markovian one.
- We probe nuclear and electron spins in a single molecule even beyond the electromagnetic dipole selection rules, at readily accessible magnetic fields (few mT) and temperatures (5 K) by resonant radio-frequency current from a scanning tunneling microscope. We achieve subnanometer spatial resolution combined with single-spin sensitivity, representing a 10 orders of magnitude improvement compared to existing magnetic resonance techniques. We demonstrate the successful resonant spectroscopy of the complete manifold of nuclear and electronic magnetic transitions of up to $\mathrm{$\Delta${}}{I}_{z}=\ifmmode\pm\else\textpm\fi{}3$ and $\mathrm{$\Delta${}}{J}_{z}=\ifmmode\pm\else\textpm\fi{}12$ of single quantum spins in a single molecule. Our method of resonant radio-frequency scanning tunneling spectroscopy offers, atom-by-atom, unprecedented analytical power and spin control with an impact on diverse fields of nanoscience and nanotechnology.
- We study theoretically quantum dynamics of interacting bosons in artificial magnetic fields as engineered in recent ultracold atomic experiments, where quantum cyclotron orbital motion has been observed. With exact numerical simulations and perturbative analyses, we find that interactions induce damping in the cyclotron motion. The damping time is found to be dependent on interaction and tunneling strengths monotonically, while its dependence on magnetic flux is nonmonotonic. Sufficiently strong interactions would render bosons dynamically localized, inhibiting the cyclotron motion. The damping predicted by us can be construed as an interaction-induced quantum decoherence of the cyclotron motion.
- We propose a real-space renormalization group method to explicitly decouple into independent components a many-body system that, as in the phenomenon of spin-charge separation, exhibits separation of degrees of freedom at low energies. Our approach produces a branching holographic description of such systems that opens the path to the efficient simulation of the most entangled phases of quantum matter, such as those whose ground state violates a boundary law for entanglement entropy. As in the coarse-graining transformation of Vidal [Phys. Rev. Lett. 99, 220405 (2007)
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publications (hide)103
- (2015)cite arxiv:1505.02924Comment: 24 pages, 5 figures, published in Jour. Stat. Mech.
- (2014)cite arxiv:1412.0202Comment: 6 pages, 4 figures, version published in EPL + Supplementary Material on the scaling of time-fluctuations.
- Phys. Rev. Lett., 114 (3): 034102 (January 2015)
- Phys. Rev. Lett., 113 (24): 240403 (December 2014)
- Phys. Rev. Lett., 108 (24): 240402 (June 2012)
- Phys. Rev. A, 87 (3): 032102 (March 2013)
- (2013)cite arxiv:1306.0642.
- (2014)cite arxiv:1410.0464Comment: 5pages, 3 figures.
- (2014)cite arxiv:1412.3828Comment: 6 pages+appendix, 2 figures.
- (2014)cite arxiv:1412.6991Comment: 19 pages, 4 figures.
- Phys. Rev. Lett., 113 (25): 250601 (December 2014)
- Phys. Rev. A, 90 (4): 043613 (October 2014)
- (2014)cite arxiv:1411.1388.
- (2014)cite arxiv:1410.6632Comment: 14 pages, 11 figures.
- (2014)cite arxiv:1410.6525Comment: 6 pages, 3 figures.
- (2014)cite arxiv:1408.3301Comment: Feedback encouraged. 9 Pages, 4 Figures, 4 Tables. The author thanks JSPS for financial support.
- (2014)cite arxiv:1407.8536Comment: Draft of a review paper. Section 4 and section 5 are still required to be updated.
- (2014)cite arxiv:1407.8203Comment: 91 pages, 8 figures.
- (2014)cite arxiv:1404.3507Comment: 22 pages, 2 figures.
- (2014)cite arxiv:1407.6171Comment: (Extended).
