Macroscopic Quantum Tunneling

Macroscopic Quantum Tunneling in Magnetic Nanostructures

Theoretical foundations of the problem of quantum spin tunneling in magnetic nanostructures are presented. Several model problems are considered in detail, including recent new results on tunneling in antiferromagnetic nanoparticles and topologically nontrivial magnetic structures in systems with reduced dimension.

Quantum terahertz electrodynamics and macroscopic quantum tunneling in layered superconductors.

We derive a quantum field theory of Josephson plasma waves (JPWs) in layered superconductors, which describes two types of interacting JPW bosonic quanta (one heavy and one lighter). We propose a mechanism of enhancement of macroscopic quantum tunneling (MQT) in stacks of intrinsic Josephson junctions. Because of the long-range interaction between junctions in layered superconductors, the calcu...

Effects of dissipation and temperature on macroscopic quantum tunneling.

Enhancement of macroscopic quantum tunneling by Landau-Zener transitions.

Motivated by recent realizations of qubits with a readout by macroscopic quantum tunneling in a Josephson junction, we study the problem of barrier penetration in the presence of coupling to a spin-1 / 2 system. It is shown that, when the diabatic potentials for fixed spin intersect in the barrier region, Landau-Zener transitions lead to an enhancement of the tunneling rate. The effect of these...

Pulsed Macroscopic Quantum Tunneling of Falling Bose Condensates

We investigate macroscopic quantum tunneling of a Bose condensate and how it is affected by the interatomic interaction. We study the dynamics of a condensate falling under gravity and scattering on a Gaussian potential barrier that models a mirror formed by a far-detuned sheet of light. We observe bouncing, interference and quantum tunneling of the condensate. We find that the tunneling rate i...