Publications

Order by: publication date number of citations

• Two distinguishable impurities in BEC: squeezing and entanglement of two Bose polarons

  Christos Charalambous, Miguel A. Garcia-March, Aniello Lampo, Mohammad Mehboud, Maciej Lewenstein

  SciPost Phys. 6, 010 (2019) · published 22 January 2019 | Toggle abstract · pdf

  We study entanglement and squeezing of two uncoupled impurities immersed in a Bose-Einstein condensate. We treat them as two quantum Brownian particles interacting with a bath composed of the Bogoliubov modes of the condensate. The Langevin-like quantum stochastic equations derived exhibit memory effects. We study two scenarios: (i) In the absence of an external potential, we observe sudden death of entanglement; (ii) In the presence of an external harmonic potential, entanglement survives even at the asymptotic time limit. Our study considers experimentally tunable parameters.

  20 citations

• Non-equilibrium quasiparticles in superconducting circuits: photons vs. phonons

  Gianluigi Catelani, Denis M. Basko

  SciPost Phys. 6, 013 (2019) · published 29 January 2019 | Toggle abstract · pdf

  We study the effect of non-equilibrium quasiparticles on the operation of a superconducting device (a qubit or a resonator), including heating of the quasiparticles by the device operation. Focusing on the competition between heating via low-frequency photon absorption and cooling via photon and phonon emission, we obtain a remarkably simple non-thermal stationary solution of the kinetic equation for the quasiparticle distribution function. We estimate the influence of quasiparticles on relaxation and excitation rates for transmon qubits, and relate our findings to recent experiments.

  11 citations

• (1,0) gauge theories on the six-sphere

  Usman Naseer

  SciPost Phys. 6, 002 (2019) · published 8 January 2019 | Toggle abstract · pdf

  We construct gauge theories with a vector-multiplet and hypermultiplets of $(1,0)$ supersymmetry on the six-sphere. The gauge coupling on the sphere depends on the polar angle. This has a natural explanation in terms of the tensor branch of $(1,0)$ theories on the six-sphere. For the vector-multiplet we give an off-shell formulation for all supersymmetries. For hypermultiplets we give an off-shell formulation for one supersymmetry. We show that the path integral for the vector-multiplet localizes to solutions of the Hermitian-Yang-Mills equation, which is a generalization of the (anti-)self duality condition to higher dimensions. For the hypermultiplet, the path integral localizes to configurations where the field strengths of two complex scalars are related by an almost complex structure.

  4 citations

• Adiabatic state distribution using anti-ferromagnetic spin systems

  Koen Groenland

  SciPost Phys. 6, 011 (2019) · published 23 January 2019 | Toggle abstract · pdf

  Transporting quantum information is an important prerequisite for quantum computers. We study how this can be done in Heisenberg-coupled spin networks using adiabatic control over the coupling strengths. We find that qudits can be transferred and entangled pairs can be created between distant sites of bipartite graphs with a certain balance between the maximum spin of both parts, extending previous results that were limited to linear chains. The transfer fidelity in a small star-shaped network is numerically analysed, and possible experimental implementations are discussed.

  2 citations

• Thermoelectric coefficients and the figure of merit for large open quantum dots

  Robert S. Whitney, Keiji Saito

  SciPost Phys. 6, 012 (2019) · published 24 January 2019 | Toggle abstract · pdf

  We consider the thermoelectric response of chaotic or disordered quantum dots in the limit of phase-coherent transport, statistically described by random matrix theory. We calculate the full distribution of the thermoelectric coefficients (Seebeck $S$ and Peltier $\Pi$), and the thermoelectric figure of merit $ZT$, for large open dots at arbitrary temperature and external magnetic field, when the number of modes in the left and right leads ($N_{\rm L}$ and $N_{\rm R}$) are large. Our results show that the thermoelectric coefficients and $ZT$ are maximal when the temperature is half the Thouless energy, and the magnetic field is negligible. They remain small, even at their maximum, but they exhibit a type of universality at all temperatures, in which they do not depend on the asymmetry between the left and right leads $(N_{\rm L}-N_{\rm R})$, even though they depend on $(N_{\rm L}+N_{\rm R})$.