Search results for "Quantum"
showing 10 items of 9714 documents
Quantum Non-Markovian Piecewise Dynamics from Collision Models
2017
Recently, a large class of quantum non-Markovian piecewise dynamics for an open quantum system obeying closed evolution equations has been introduced [B. Vacchini, Phys. Rev. Lett. 117, 230401 (2016)]. These dynamics have been defined in terms of a waiting-time distribution between quantum jumps, along with quantum maps describing the effect of jumps and the system's evolution between them. Here, we present a quantum collision model with memory, whose reduced dynamics in the continuous-time limit reproduces the above class of non-Markovian piecewise dynamics, thus providing an explicit microscopic realization.
Non-adiabatic vacuum induced berry phase
2016
We investigate quantum effects in geometric phases arising when a two-level system is interacting with a quantized electromagnetic field.
Very narrow quantum OBDDs and width hierarchies for classical OBDDs
2014
In the paper we investigate a model for computing of Boolean functions - Ordered Binary Decision Diagrams (OBDDs), which is a restricted version of Branching Programs. We present several results on the comparative complexity for several variants of OBDD models. - We present some results on the comparative complexity of classical and quantum OBDDs. We consider a partial function depending on a parameter k such that for any k > 0 this function is computed by an exact quantum OBDD of width 2, but any classical OBDD (deterministic or stable bounded-error probabilistic) needs width 2 k+1. - We consider quantum and classical nondeterminism. We show that quantum nondeterminism can be more efficien…
Nonlinear dissipation phenomena in optomechanics
2016
Yksikään kvanttisysteemi ei voi olla täysin eristetty ympäristöstään, mikä johtaa informaation välittymiseen systeemin ja ympäristön välillä. Optomekaniikassa, missä tyypillinen tutkittava systeemi on peileistä koostuva optinen kaviteetti yhdistettynä mekaaniseen värähtelijään, systeemin ja ympäristön lineaarisesta kytkennästä johtuvat dissipaatioilmiöt ovat hyvin tunnettuja. Epälineaarisia ilmiöitä ei kuitenkaan ymmärretä yhtä laajasti. Tutkin epälineaarista kytkentää kaviteetin ja lämpökylvyn välillä ja havainnollistan tästä kytkennästä johtuvia ilmiöitä kuten epälineaarista dissipaatiota. Esitän myös optisen kaviteetin epälineaarisen dissipaation oikeuttavan mallin, missä optinen kavitee…
Towards Process Centered Architecting for Quantum Software Systems
2022
Quantum Software Engineering (QSE) is a recent trend - focused on unifying the principles of quantum mechanics and practices of software engineering - to design, develop, validate, and evolve quantum age software systems and applications. Software architecture for quantum computing (a.k. a. quantum software architectures (QSA)) supports the design, development, and maintenance etc. phases of quantum software systems using architectural components and connectors. QSA can enable quantum software designers and developers to map the operations of Qubits to architectural components and connectors for implementing quantum software. This research aims to explore the role of QSAs by investigating (…
Recovering quantum correlations in classical environments without backaction: observation and interpretation
2014
Quantum correlations (entanglement, discord, nonlo-cality) present in a composite quantum system are essential resources for quantum information processing [1, 2]. However, the exploitation of these quantum resources is jeopardized by the detrimental effects of the environment surrounding the quantum system. For instance under Markovian noise, they decay asymptotically or disappear at a finite time [3, 4]. This drawback leads one to look for conditions where quantum correlations can be recovered during the evolution. To this aim non-Markovian noise, arising from strong couplings or structured environments, has been shown to be fundamental because of its memory effects. In fact, in the case …
Decoherence without entanglement and quantum Darwinism
2020
It is often assumed that decoherence arises as a result of the entangling interaction between a quantum system and its environment, as a consequence of which the environment effectively measures the system, thus washing away its quantum properties. Moreover, this interaction results in the emergence of a classical objective reality, as described by quantum Darwinism. In this Rapid Communication, we show that the idea that entanglement is needed for decoherence is imprecise. We propose a dynamical mixing mechanism capable of inducing decoherence dynamics on a system without creating any entanglement with its quantum environment. We illustrate this mechanism by introducing a simple and exactl…
Ge quantum well plasmon-enhanced quantum confined Stark effect modulator
2014
ABSTRACTWe theoretically and experimentally investigate a novel modulation concept on silicon (Si) based on the combination of quantum confinement and plasmon enhancement effects. We experimentally study the suitability of Ge/SiGe quantum wells (QWs) on Si as the active material for a plasmon-enhanced optical modulator. We demonstrate that in QW structures absorption and modulation of light with transverse magnetic (TM) polarization are greatly enhanced due to favorable selection rules. Later, we theoretically study the plasmon propagation at the metal-Ge/SiGe QW interface. We design a novel Ge/SiGe QW structure that allows maximized overlap between the plasmonic mode and the underlying Ge/…
Unravelling the Intertwined Atomic and Bulk Nature of Localised Excitons by Attosecond Spectroscopy
2021
The electro-optical properties of most semiconductors and insulators of technological interest are dominated by the presence of electron-hole quasi-particles, called excitons. The manipulation of excitons in dielectrics has recently received great attention, with possible applications in different fields including optoelectronics and photonics. Here, we apply attosecond transient reflection spectroscopy in a sequential two-foci geometry and observe sub-femtosecond dynamics of a core-level exciton in bulk MgF2 single crystals. Furthermore, we access absolute phase delays, which allow for an unambiguous comparison with theoretical calculations. Our results show that excitons surprisingly exhi…
Theoretical and computational studies of magnetic anisotropy and exchange coupling in molecular systems
2018
The field of molecular magnetism studies the magnetic properties of molecular systems as opposed to conventional metal-based magnets. The high chemical modifiability of the constituting molecules makes such materials highly versatile, and the small size of the building blocks leads to the rise of various quantum mechanical phenomena, such as tunneling and entanglement. These phenomena can then be further utilized in the construction of nanoscale quantum devices. This dissertation describes computational and theoretical studies in the field of molecular magnetism using state-of-the-art quantum chemical methods based on ab initio multireference approaches and broken symmetry density functional t…