Mechanisms of Decoherence at Low Temperatures

Abstract

We briefly review the oscillator and spin bath models of quantum environments, which can be used to describe the low-energy dynamics of open quantum systems. We then use them to discuss both the mechanisms causing decoherence at low $T$, and the dynamics of this decoherence. This is done first for a central 2-level system coupled to these environments- the results can be applied to the dynamics of quantum nanomagnets and superconducting SQUIDs, where large-scale tunneling of magnetisation and flux take place. Decoherence in these systems is caused principally by coupling to electrons and nuclear spins, the spin bath couplings are particularly dangerous at low $T$. These models are also generalised to discuss quantum measurements in which the measured system, the measuring apparatus, and the environment are treated quantum mechanically. The results can be used to calculate the dynamics of coupled SQUIDs and/or nanomagnets, in which one acts as a measuring apparatus and the other exhibits large-scale quantum superpositions. The same model can be used to describe coupled qubits.

Typos corrected, invited article to appear in special issue of Chemical Physics on "Quantum Physics of Open Systems"

References in corpus (22)

• Quantum Computing
• Theory of the spin bath
• Intrinsic Decoherence in Mesoscopic Systems
• On the low energy properies of fermions with singular interactions
• Quantum Gravity as a Dissipative Deterministic System
• Low-Temperature Quantum Relaxation in a System of Magnetic Nanomolecules
• Non-Fermi Liquid Fixed Point in 2+1 Dimensions
• Low Energy Dynamics of the Spinon-Gauge System
• Observation of the distribution of molecular spin states by resonant quantum tunneling of the magnetization
• Gauge-invariant response functions of fermions coupled to a gauge field
• Renormalization Group Approach to Low Temperature Properties of a Non-Fermi Liquid Metal
• The effects of nuclear spins on the quantum relaxation of the magnetization for the molecular nanomagnet Fe_8
• Quantum Relaxation of Magnetisation in Magnetic Particles
• Nuclear spin driven resonant tunnelling of magnetisation in Mn12 acetate
• Macroscopic Quantum Tunneling of a Domain Wall in a Ferromagnetic Metal
• Finite-Wavevector Electromagnetic Response of Fractional Quantized Hall States
• Quantum Coherence in Fe8 Molecular Nanomagnets
• Non-Fermi Liquid Behavior In Quantum Critical Systems
• Dynamics of a Pair of Interacting Spins Coupled to an Environmental Sea
• Effective Hamiltonian in the Problem of a "Central Spin" Coupled to a Spin Environment
• Influence of gauge-field fluctuations on composite fermions near the half-filled state
• Quantum Environments: Spin Baths, Oscillator Baths, and applications to Quantum Magnetism

Cited by in corpus (19)

• Quantum Coherence in an Exchange-Coupled Dimer of Single-Molecule Magnets
• Quantum Decoherence
• Spin-Based Quantum Computers made by Chemistry: Hows and Whys
• Entanglement Sharing and Decoherence in the Spin-Bath
• Universal Scaling of Hyperfine-Induced Electron Spin Echo Decay
• Suppression of decoherence via strong intra-environmental coupling
• Searching for Decoherence-Free Subspaces in Cavity Quantum Electrodynamics
• Decoherence in a N-qubit solid-state quantum computer
• Non-Markoffian effects of a simple nonlinear bath
• Master-equations for the study of decoherence
• Flux-vector model of spin noise in superconducting circuits: Electron versus nuclear spins and role of phase transition
• Crossovers in spin-boson and central spin models
• An Anisotropic Landau-Lifschitz-Gilbert model of dissipation in qubits
• Relating Heat and Entanglement in Strong Coupling Thermodynamics
• Physics at the FQMT'04 conference
• A Quantum Model for Entropic Springs
• Effects of a nonlinear bath at low temperatures
• Targeting Eigenstates by "Simulated Measurements" using a Decoherence based Nonlinear Schrödinger Equation
• Comparison between Decoherence time for a Two-state Spin 1/2 System with Its Corresponding Quantum Retrieval Period