Journal reference: Ann. Phys. 525, No. 10-11, 827-832 (2013)
DOI: 10.1002/andp.201300090
A string of repulsively interacting particles exhibits a phase transition to a zigzag structure, by reducing the transverse trap potential or the interparticle distance. The transition is driven by transverse, short wavelength vibrational modes.
Journal reference: New J. Phys. 16, 093022 (2014)
DOI: 10.1088/1367-2630/16/9/093022
Ultra fast and accurate quantum operations are required in many modern scientific areas - for instance quantum information, quantum metrology and magnetometry. However the accuracy is limited if the Rabi frequency is comparable with the transition frequency due to the breakdown of the rotating wave approximation (RWA). Here we report the experimental implementation of a method based on optimal control theory, which does not suffer these restrictions.
Journal reference: New J. Phys. 16, 075007 (2014)
DOI: 10.1088/1367-2630/16/7/075007
We investigate the performance of different control techniques for ion transport in state-of-the-art segmented miniaturized ion traps. We employ numerical optimization of classical trajectories and quantum wavepacket propagation as well as analytical solutions derived from invariant based inverse engineering and geometric optimal control.
Journal reference: Phys. Rev. A 89, 042322 (2014)
DOI: http://dx.doi.org/10.1103/PhysRevA.89.042322
We demonstrate that arbitrary time evolutions of many-body quantum systems can be reversed even in cases when only part of the Hamiltonian can be controlled. The reversed dynamics obtained via optimal control --contrary to standard time-reversal procedures-- is extremely robust to external sources of noise.
Journal reference: Phys. Rev. B 89, 214408 (2014)
DOI: 10.1103/PhysRevB.89.214408
We study the crossover from classical to quantum phase transitions at zero temperature within the framework of ϕ4 theory. The classical transition at zero temperature can be described by the Landau theory, turning into a quantum Ising transition with the addition of quantum fluctuations. We perform a calculation of the transition line in the regime where the quantum fluctuations are weak. The calculation is based on a renormalization group analysis of the crossover between classical and quantum transitions, and is well controlled even for space-time dimensionality D below 4.
Journal reference: Phys. Rev. A 89, 032334 (2014)
DOI: 10.1103/PhysRevA.89.032334
We investigate the implementation of a controlled-Z gate on a pair of Rydberg atoms in spatially separated dipole traps where the joint excitation of both atoms into the Rydberg level is strongly suppressed (the Rydberg blockade). We follow the adiabatic gate scheme of Jaksch et al.
Journal reference: Phys. Rev. B 89, 094103 (2014)
DOI: 10.1103/PhysRevB.89.094103
Ions of the same charge inside confining potentials can form crystalline structures which can be controlled by means of the ions density and of the external trap parameters. In particular, a linear chain of trapped ions exhibits a transition to a zigzag equilibrium configuration, which is controlled by the strength of the transverse confinement.
DOI: 10.1103/PhysRevLett.112.250502
Journal reference: Phys. Rev. Lett. 112, 250502 (2014)
We propose a simple idea for realizing a quantum gate with two identical fermions in a double well trap via external optical pulses without addressing the atoms individually. The key components of the scheme are Feshbach resonance and Pauli blocking, which decouple unwanted states from the dynamics.
Journal reference: New J. Phys. 16 103015 (2014)
DOI: 10.1088/1367-2630/16/10/103015
We present a unified framework to describe lattice gauge theories by means of tensor networks: this framework is efficient as it exploits the high amount of local symmetry content native of these systems describing only the gauge invariant subspace.
Journal reference: Nature Communications 5, 4009 (2014)
DOI: 10.1038/ncomms5009
Cite as: arXiv:1402.0377 [quant-ph]
We demonstrate a two-pulse Ramsey-type interferometer for non-classical motional states of a Bose-Einstein condensate in an anharmonic trap. The control pulses used to manipulate the condensate wavefunction are obtained from Optimal Control Theory and directly optimised to maximise the interferometric contrast.