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Single-Bit Feedback And Quantum-Dynamical Decoupling, Francesco Ticozzi, Lorenza Viola
Single-Bit Feedback And Quantum-Dynamical Decoupling, Francesco Ticozzi, Lorenza Viola
Dartmouth Scholarship
Synthesizing an effective identity evolution in a target system subjected to unwanted unitary or nonunitary dynamics is a fundamental task for both quantum control and quantum information processing applications. Here, we investigate how single-bit, discrete-time feedback capabilities may be exploited to enact or to enhance quantum procedures for effectively suppressing unwanted dynamics in a finite-dimensional open quantum system. An explicit characterization of the joint unitary propagators correctable by a single-bit feedback strategy for arbitrary evolution time is obtained. For a two-dimensional target system, we show how by appropriately combining quantum feedback with dynamical decoupling methods, concatenated feedback-decoupling schemes may be …
Quantum Entanglement Via Nilpotent Polynomials, Aikaterini Mandilara, Vladimir M. Akulin, Andrei V. Smilga, Lorenza Viola
Quantum Entanglement Via Nilpotent Polynomials, Aikaterini Mandilara, Vladimir M. Akulin, Andrei V. Smilga, Lorenza Viola
Dartmouth Scholarship
We propose a general method for introducing extensive characteristics of quantum entanglement. The method relies on polynomials of nilpotent raising operators that create entangled states acting on a reference vacuum state. By introducing the notion of tanglemeter, the logarithm of the state vector represented in a special canonical form and expressed via polynomials of nilpotent variables, we show how this description provides a simple criterion for entanglement as well as a universal method for constructing the invariants characterizing entanglement. We compare the existing measures and classes of entanglement with those emerging from our approach. We derive the equation of motion …
Multipartite Entanglement Generation And Fidelity Decay In Disordered Qubit Systems, Simone Montangero, Lorenza Viola
Multipartite Entanglement Generation And Fidelity Decay In Disordered Qubit Systems, Simone Montangero, Lorenza Viola
Dartmouth Scholarship
We investigate multipartite entanglement dynamics in disordered spin-1∕2 lattice models exhibiting a transition from integrability to quantum chaos. Borrowing from the generalized entanglement framework, we construct measures for correlations relative to arbitrary local and bilocal spin observables, and show how they naturally signal the crossover between distinct dynamical regimes. Analytical estimates are obtained in the short- and long-time limits. Our results are in qualitative agreement with predictions from the random matrix theory and are relevant to both condensed-matter physics and to the stability of quantum information in disordered quantum computing hardware.