Summer 2016

Intermolecular Potentials from the Iterated Stockholder Atoms Approach

Speaker(s): 
Alston Misquitta
Dates: 
Friday, July 8, 2016 - 2:00pm

The Iterated Stockholder Atom (ISA) algorithm [1] is proving to be one of the most interesting methods for atoms‐in‐a‐molecule (AIM): it leads to a unique definition of the atoms which are guaranteed to be maximally spherical while allowing for the effects of charge movement as a result of chemical bonding. Through a basis‐space, or BS‐ISA, algorithm [2] we are able to calculate the ISA solution at the basis‐set...

Xion-Jun Liu (Peking University): Symmetry-Protected Non-Abelian Braiding of Majorana Kramers' Pairs

Topological superconductors, which host Majorana zero modes, are a most attractive research topic in condensed matter physics. Due to the Kramers theorem, in a time-reversal invariant topological superconductor the Majorana modes come in pairs, called Majorana Kramer pairs (MKPs). The recent study showed that, due to the time-reversal symmetry protection, the MKPs may obey non-Abelian braiding statistics, while it was later suggested that local rotation among a single MKP may cause errors in MKP-based qubits. In the work presented in this talk, I shall show the complete symmetry condition for non-Abelian braiding of MKPs. By introducing an effective Hamiltonian approach to describe the braiding of MKPs, we show that the ideal non Abelian braiding is protected when the effective Hamiltonian exhibits a new time-reversal like anti-unitary symmetry, which is satisfied if the system is free of dynamical noise. On the other hand, the presence of dynamical noise may bring about decoherence only when the correlation function of such noise breaks the time-reversal like symmetry in the time domain. Interestingly, the resulted error is found to be a higher order effect, compared with the decoherence of Majorana qubits without time-reversal symmetry protection, caused by the dynamical perturbations. These results show that the non-Abelian braiding of MKPs is observable and may have versatile applications to future quantum computation technologies.
 

Symmetry-Protected Non-Abelian Braiding of Majorana Kramers' Pairs

Speaker(s): 
Xiong-Jun Liu
Dates: 
Tuesday, July 5, 2016 - 3:30pm

Topological superconductors, which host Majorana zero modes, are a most attractive research topic in condensed matter physics. Due to the Kramers theorem, in a time-reversal invariant topological superconductor the Majorana modes come in pairs, called Majorana Kramer pairs (MKPs). The recent study showed that, due to the time-reversal symmetry protection, the MKPs may obey non-Abelian braiding statistics, while it was...

Control of Active Liquid Crystals by Means of Addressable Soft Interfaces

Speaker(s): 
Jordi Ignes
Dates: 
Thursday, July 28, 2016 - 4:00pm

Active liquid crystals are aqueous in vitro suspensions of cytoskeletal proteins that self-assemble into elongated fibers and develop sustained flows at the continuous expense of ATP. When they condense on soft interfaces, the aligned fibers organize into non equilibrium analogs of passive liquid crystals. However, proteins do not respond to external electromagnetic fields, unlike liquid crystals, which are readily reconfigured inside devices. We demonstrate a reversible and bio-compatible experimental protocol to align an active liquid crystal with a uniform...