On the theory of collective rotations

Brian H Buck, Lawrence C. Biedenharn, R. Y. Cusson

Michel Baranger, Judit Németh

Pan Ri-jing

A two-way quantum secure direct communication protocol against a collective rotation noise is presented.The protocol encodes one logical bit in two-qubit noiseless states,and so it can function over a quantum channel subjected to collective rotation.Since there is no basis mismatch in the decoding process,the intrinsic high efficiency is achieved.Moreover,the security of the proposed protocol against some common attacks is analysed,which shows that it is secure in theory.

James Mc Connell

Teruo Kishimoto, Tetsuo Kammuri

A many•body technique called the dynamical nuclear field theory is developed by taking the example of pair rotation.The time-dependent one-body Hamiltonian contains the collective coordinates; the magnitude and phase aIigleof the energy gap.Effective forms of the original Hamiltonian and other operators are derived for a direct-product space of the collective states and a restricted set of the particle states defined by the driving Hamiltonian in the intrinsic frame.Pair rotations of even-and odd-A systems are treated in the lowest order approximation.The particle-rotor picture and the cranking model are shown to be equivalent.*) Brief report on DNFT in the Tamm-Dancoff approximation can be found in Ref. 13).

Mi­chael Urban

There are several situations in which the collective motion of a superfluid Fermi gas is coupled to quasiparticle excitations. Quasiparticle excitations are, for example, present at finite temperature, but also at zero temperature in the case of a rotating trap. In this paper, I present a semiclassical description of such systems, where the superfluid component is described by hydrodynamics while the normal component, formed by the quasiparticles, is described by a transport equation similar to the Vlasov equation. The coupling between the two components generates a strong damping of the collective modes. As applications of the semiclassical theory, the case of a rotating trap and several collective modes (quadrupole and scissors modes) of the trapped gas are discussed.