Індекс рубрикатора НБУВ: В368.31

Рубрики:

Надпровідність. Надпровідники

Шифр НБУВ: Ж14063 Пошук видання у каталогах НБУВ 

A technique for studying collisionless dynamics of a homogeneous superconducting system is developed which is based on Riccati parametrization of the Wigner distribution function. The quantum evolution of the superconducting order parameter, initially deviating from the equilibrium value, is calculated using this technique. The effect of a time-dependent BCS paring interaction on the dynamics of the order parameter is also studied.

When a two-level quantum system is irradiated with a microwave signal in resonance with the energy difference between the levels, it starts Rabi oscillations between those states. If there are other states close, in energy, to the first two, the microwave signal will also induce transitions to those. Here we study the probability of transition to the third state, in a three-level system, while Rabi oscillations between the first two states are performed. We investigate the effect of pulse shaping on the probability and suggest methods for optimizing the pulse shapes to reduce the transition probability.

Індекс рубрикатора НБУВ: В152.54

Рубрики:

Алгебри

Шифр НБУВ: Ж41243 Пошук видання у каталогах НБУВ 

Measurement of the energy eigenvalues (spectrum) of a multi-qubit system has recently become possible by qubit tunneling spectroscopy (QTS). In the standard QTS experiments, an incoherent probe qubit is strongly coupled to one of the qubits of the system in such a way that its incoherent tunneling rate provides information about the energy eigenvalues of the original (source) system. In this paper, we generalize QTS by coupling the probe qubit to many source qubits. We show that by properly choosing the couplings, one can perform projective measurements of the source system energy eigenstates in an arbitrary basis, thus performing quantum eigenstate tomography. As a practical example of a limited tomography, we apply our scheme to probe the eigenstates of a kink in a frustrated transverse Ising chain.