Exchange interaction, entanglement, and quantum noise due to a thermal bosonic field

Abstract

We analyze the indirect exchange interaction between two two-state systems, e.g., spins 1/2, subject to a common finite-temperature environment modeled by bosonic modes. The environmental modes, e.g., phonons or cavity photons, are also a source of quantum noise. We analyze the coherent vs noise-induced features of the two-spin dynamics and predict that for low enough temperatures the induced interaction is coherent over time scales sufficient to create entanglement. A nonperturbative approach is utilized to obtain an exact solution for the onset of the induced interaction, whereas for large times, a Markovian scheme is used. We identify the time scales for which the spins develop entanglement for various spatial separations. For large enough times, the initially created entanglement is erased by quantum noise. Estimates for the interaction and the level of quantum noise for localized impurity electron spins in Si-Ge type semiconductors are given.

Modeling of quantum-information processing with Ehrenfest guided trajectories: A case study with spin-boson-like couplings

“…The notion of entangling separated systems and of distributing quantum coherence by interaction with common heat baths or other incoherent means is well established in the quantum information and condensed matter communities, and has been explored under a number of -either more specific and applied or more general and abstract -viewpoints [52][53][54][55][56][57][58][59][60][61][62][63][64][65][66]. However, the problem of studying the non-perturbative interaction of two qubits with a common bath is still in general a difficult one.…”

Dissipation-driven generation of two-qubit entanglement mediated by plasmonic waveguides

“…There have been many works analyzing the coupling of qubits provided by the interchange of fermions or bosons 2,3 and, in particular, addressing the generation of entanglement due to the coupling to a common bath. [4][5][6][7] Within this context, the EM field may constitute the agent needed to prepare a system in a targeted entangled state or to couple two preexisting entangled systems. In a number of proposed schemes qubit-qubit interactions are provided either by coupling to a common EM cavity mode [8][9][10][11][12] or, when large separations between the qubits are desired, to a guided mode.…”

Study of Decoherence of Elementary Gates Implemented in a Chain of Few Nuclear Spins Quantum Computer Model

“…Unfortunately, there is not a general unique master equation which could be used for any quantum system in interaction with the environment, and there is not a unified consensus about the best approach for studying a given quantum system interacting with the environment and/or the measurement apparat [3]. Additionally, the environment can be taken as bosonic [24][25][26][27][28][29] or fermionic [27], and the interaction between quantum and environment system is taken as a constant force (the potential is just the product of the variables of the quantum system with the environment system). In most of the approaches, the positiveness and trace equal to one are kept as principal condition for the reduced density matrix.…”