Quantum Zeno effect, adiabaticity and dynamical superselection rules

Quantum Zeno subspaces and dynamical superselection rules

The quantum Zeno evolution of a quantum system takes place in a proper subspace of the total Hilbert space. The physical and mathematical features of the "Zeno subspaces" depend on the measuring apparatus: when this is included in the quantum description, the Zeno effect becomes a mere consequence of the dynamics and, remarkably, can be cast in terms of an adiabatic theorem, with a dynamical superselection rule. We look at several examples and focus on quantum computation and decoherence-free subspaces.

通过自适应量子泽诺测量实现绝热性的捷径

Shortcuts to Adiabaticity via Adaptive Quantum Zeno Measurements

通过自适应量子泽诺测量实现绝热性捷径，利用非绝热几何连接和反迪巴蒂克驱动统一框架。

On noise-induced superselection rules

The dynamical properties of a quantum system can be profoundly influenced by its environment. Usually, the environment provokes decoherence and its action on the system can often be schematized by adding a noise term in the Hamiltonian. However, other scenarios are possible: we show that by increasing the strength of the noise, the Hilbert space of the system gradually splits into invariant subspaces, among which transitions become increasingly difficult. The phenomenon is equivalent to the formation of the quantum Zeno subspaces. We explore the possibility that noise can {\em prevent}, rather…

量子芝诺发动机与热泵

Quantum Zeno Engines and Heat Pumps

本文提出用量子芝诺冲程替代绝热变换构建量子发动机与热泵，并以量子谐振子为例证明其最优性能可比绝热捷径技术更快实现。

Quantum state transfer in spin chains via shortcuts to adiabaticity

Based on shortcuts to adiabaticity and quantum Zeno dynamics, we present a protocol to implement quantum state transfer (QST) in a quantum spin-1/2 chain. In the protocol, the complex Hamiltonian of an $N$-site system is simplified, and a simple effective Hamiltonian is present. It is shown that only the control of the coupling strengths between the boundary spins and the bulk spins are required for QST. Numerical simulations demonstrate that the protocol possesses high efficiency and is robust against the decay and the fluctuations of the control fields. The protocol might provide an alternat…

Unification of Dynamical Decoupling and the Quantum Zeno Effect

We unify the quantum Zeno effect (QZE) and the "bang-bang" (BB) decoupling method for suppressing decoherence in open quantum systems: in both cases strong coupling to an external system or apparatus induces a dynamical superselection rule that partitions the open system's Hilbert space into quantum Zeno subspaces. Our unification makes use of von Neumann's ergodic theorem and avoids making any of the symmetry assumptions usually made in discussions of BB. Thus we are able to generalize BB to arbitrary fast and strong pulse sequences, requiring no symmetry, and to show the existence of two alt…