State Transfer and Analysis of Quantum Systems on the Bloch Sphere

2014 ◽  
pp. 21-37
2013 ◽  
Vol 2013 ◽  
pp. 1-8
Author(s):  
Shouwei Zhao ◽  
Jitao Sun ◽  
Hai Lin

The state transfer problem of a class of nonideal quantum systems is investigated. It is known that traditional Lyapunov methods may fail to guarantee convergence for the nonideal case. Hence, a hybrid impulsive control is proposed to accomplish a more accurate convergence. In particular, the largest invariant sets are explicitly characterized, and the convergence of quantum impulsive control systems is analyzed accordingly. Numerical simulation is also presented to demonstrate the improvement of the control performance.


Author(s):  
T. N. Palmer

An arbitrarily dense discretization of the Bloch sphere of complex Hilbert states is constructed, where points correspond to bit strings of fixed finite length. Number-theoretic properties of trigonometric functions (not part of the quantum-theoretic canon) are used to show that this constructive discretized representation incorporates many of the defining characteristics of quantum systems: completementarity, uncertainty relationships and (with a simple Cartesian product of discretized spheres) entanglement. Unlike Meyer’s earlier discretization of the Bloch Sphere, there are no orthonormal triples, hence the Kocken–Specker theorem is not nullified. A physical interpretation of points on the discretized Bloch sphere is given in terms of ensembles of trajectories on a dynamically invariant fractal set in state space, where states of physical reality correspond to points on the invariant set. This deterministic construction provides a new way to understand the violation of the Bell inequality without violating statistical independence or factorization, where these conditions are defined solely from states on the invariant set. In this finite representation, there is an upper limit to the number of qubits that can be entangled, a property with potential experimental consequences.


2014 ◽  
Vol 39 (4) ◽  
pp. 360-370 ◽  
Author(s):  
Shuang CONG ◽  
Long-Zhen HU ◽  
Fei YANG ◽  
Jian-Xiu LIU

Author(s):  
E.O. Kiktenko ◽  
A.K. Fedorov ◽  
V.I. Man’ko

AbstractTeleportation protocol is conventionally treated as a method for quantum state transfer between two spatially separated physical carriers. Recent experimental progress in manipulation with high-dimensional quantum systems opens a new framework for implementation of teleportation protocols. We show that the one-qubit teleportation can be considered as a state transfer between subspaces of the whole Hilbert space of an indivisible eight-dimensional system. We explicitly show all corresponding operations and discuss an alternative way of implementation of similar tasks.


Author(s):  
Juju Hu ◽  
Qiang Ke ◽  
Yinghua Ji

It has long been interest to control the transfer of population between specified quantum states and protect the coherence of the system at the same time. In this paper, we investigate a scheme to improve the strategy of state transfer for open quantum systems using no-knowledge measurement-based feedback control and reverse engineering. In order to ensure that the system can process information effectively, we first design the control pulse in advance from the perspective of population and coherence and then verify it through numerical simulations. The research results show that, based on the designed control pulse, we can indeed drive the system from any initial state to the desired target state, and the coherence of the system can be effectively protected during the state transition.


2013 ◽  
Vol 39 (4) ◽  
pp. 360-370 ◽  
Author(s):  
Shuang CONG ◽  
Long-Zhen HU ◽  
Fei YANG ◽  
Jian-Xiu LIU

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