Search results for "Quantum Systems"
showing 5 items of 85 documents
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…
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…
Superradiant Quantum Phase Transition for an Exactly Solvable Two-Qubit Spin-Boson Model
2023
A spin-boson-like model with two interacting qubits is analysed. The model turns out to be exactly solvable since it is characterized by the exchange symmetry between the two spins. The explicit expressions of eigenstates and eigenenergies make it possible to analytically unveil the occurrence of first-order quantum phase transitions. The latter are physically relevant since they are characterized by abrupt changes in the two-spin subsystem concurrence, in the net spin magnetization and in the mean photon number.
Enhancing Metastability by Dissipation and Driving in an Asymmetric Bistable Quantum System.
2018
The stabilizing effect of quantum fluctuations on the escape process and the relaxation dynamics from a quantum metastable state are investigated. Specifically, the quantum dynamics of a multilevel bistable system coupled to a bosonic Ohmic thermal bath in strong dissipation regime is analyzed. The study is performed by a non-perturbative method based on the real-time path integral approach of the Feynman-Vernon influence functional. We consider a strongly asymmetric double well potential with and without a monochromatic external driving, and with an out-of-equilibrium initial condition. In the absence of driving we observe a nonmonotonic behavior of the escape time from the metastable regi…
Synchronizing Two Superconducting Qubits through a Dissipating Resonator
2021
A system consisting of two qubits and a resonator is considered in the presence of different sources of noise, bringing to light the possibility of making the two qubits evolve in a synchronized way. A direct qubit–qubit interaction turns out to be a crucial ingredient, as well as the dissipation processes involving the resonator. The detrimental role of the local dephasing of the qubits is also taken into account.