The hypothesis, foundational to most introductory textbooks treating
quantum statistical mechanics,[4] assumes that systems go to thermal equilibrium (thermalisation). The process of thermalisation erases local memory of the initial conditions. The
eigenstate thermalisation hypothesis is a hypothesis about when quantum states will undergo thermalisation and why.
Not all quantum states undergo thermalisation. Some states have been discovered which do not (see below), and their reasons for not reaching thermal equilibrium are unclear as of March 2019[update].
Some such phenomena resisting the tendency to thermalize include (see, e.g., a
quantum scar):[6]
Conventional quantum scars,[7][8][9][10] which refer to eigenstates with enhanced probability density along unstable periodic orbits much higher than one would intuitively predict from classical mechanics.
Perturbation-induced quantum scarring:[11][12][13][14][15] despite the similarity in appearance to conventional scarring, these scars have a novel underlying mechanism stemming from the combined effect of nearly-degenerate states and spatially localized perturbations,[11][15] and they can be employed to propagate quantum wave packets in a disordered quantum dot with high fidelity.[12]
Many-body quantum scars.
Many-body localisation (MBL),[16] quantum many-body systems retaining memory of their initial condition in local observables for arbitrary amounts of time.[17][18]
The hypothesis, foundational to most introductory textbooks treating
quantum statistical mechanics,[4] assumes that systems go to thermal equilibrium (thermalisation). The process of thermalisation erases local memory of the initial conditions. The
eigenstate thermalisation hypothesis is a hypothesis about when quantum states will undergo thermalisation and why.
Not all quantum states undergo thermalisation. Some states have been discovered which do not (see below), and their reasons for not reaching thermal equilibrium are unclear as of March 2019[update].
Some such phenomena resisting the tendency to thermalize include (see, e.g., a
quantum scar):[6]
Conventional quantum scars,[7][8][9][10] which refer to eigenstates with enhanced probability density along unstable periodic orbits much higher than one would intuitively predict from classical mechanics.
Perturbation-induced quantum scarring:[11][12][13][14][15] despite the similarity in appearance to conventional scarring, these scars have a novel underlying mechanism stemming from the combined effect of nearly-degenerate states and spatially localized perturbations,[11][15] and they can be employed to propagate quantum wave packets in a disordered quantum dot with high fidelity.[12]
Many-body quantum scars.
Many-body localisation (MBL),[16] quantum many-body systems retaining memory of their initial condition in local observables for arbitrary amounts of time.[17][18]