P. W. Anderson, B. I. Halperin, and C. M. Varma, Anomalous low-temperature thermal properties of glasses and spin glasses, Philosophical Magazine, vol.16, issue.1, p.1, 1972.
DOI : 10.1007/BF01399111

W. A. Phillips, Tunneling states in amorphous solids, Journal of Low Temperature Physics, vol.27, issue.3-4, p.351, 1972.
DOI : 10.1007/BF00660072

J. Joffrin and A. Levelut, Virtual phonon exchange in glasses, Journal de Physique, vol.36, issue.9, p.811, 1976.
DOI : 10.1051/jphys:01975003609081100
URL : https://hal.archives-ouvertes.fr/jpa-00208320

H. Caruzzo, E. R. Grannan, and C. C. Yu, Nonequilibrium dielectric behavior in glasses at low temperatures: Evidence for interacting defects, Physical Review B, vol.50, issue.10, p.6685, 1994.
DOI : 10.1103/PhysRevB.50.6685

C. Enss and S. Hunklinger, Incoherent Tunneling in Glasses at Very Low Temperatures, Physical Review Letters, vol.79, issue.15, p.2831, 1997.
DOI : 10.1103/PhysRevLett.79.2831

E. Thompson, G. Lawes, J. M. Parpia, and R. O. , Low Temperature Acoustic Properties of Amorphous Silica and the Tunneling Model, Physical Review Letters, vol.84, issue.20, p.4601, 2000.
DOI : 10.1103/PhysRevLett.84.4601

A. L. Burin, Y. Kagan, and I. Y. Polishchuk, Energy Transport Induced by an External Alternating Field in Strongly Disordered Media, Physical Review Letters, vol.86, issue.24, p.5616, 2001.
DOI : 10.1103/PhysRevLett.86.5616

S. Rogge, D. Natelson, B. Tigner, and D. D. Osheroff, Nonlinear dielectric response of glasses at low temperature, Physical Review B, vol.55, issue.17, p.11256, 1997.
DOI : 10.1103/PhysRevB.55.11256

G. Frossati, R. Maynard, R. Rammal, and D. Thoulouze, New dielectric properties of glasses at very low temperatures, Journal de Physique Lettres, vol.38, issue.6, p.153, 1977.
DOI : 10.1051/jphyslet:01977003806015300
URL : https://hal.archives-ouvertes.fr/jpa-00231348

J. T. Stockburger, M. Grifoni, and M. Sassetti, Nonlinear acoustic response of glasses in the tunneling model, Physical Review B, vol.51, issue.5, p.2835, 1995.
DOI : 10.1103/PhysRevB.51.2835

Y. M. Galperin, V. L. Gurevich, and D. A. Parshin, Nonlinear resonant attenuation in glasses and spectral diffusion, Physical Review B, vol.37, issue.17, p.10339, 1988.
DOI : 10.1103/PhysRevB.37.10339

W. A. Phillips, Two-level states in glasses, Reports on Progress in Physics, vol.50, issue.12, p.1657, 1987.
DOI : 10.1088/0034-4885/50/12/003

A. Abragam, The Principles of Nuclear Magnetism, 1961.

P. L. Scott and C. D. Jeffries, Spin-Lattice Relaxation in Some Rare-Earth Salts at Helium Temperatures; Observation of the Phonon Bottleneck, Physical Review, vol.127, issue.1, p.32, 1962.
DOI : 10.1103/PhysRev.127.32

P. Neu, D. R. Reichman, and R. J. Silbey, Spectral diffusion on ultralong time scales in low-temperature glasses, Physical Review B, vol.56, issue.9, p.5250, 1997.
DOI : 10.1103/PhysRevB.56.5250

Y. Yu, Effect of Noise on a Quantum Bound State, Physical Review Letters, vol.85, issue.20, p.4199, 2000.
DOI : 10.1103/PhysRevLett.85.4199

J. L. Black and B. I. Halperin, Spectral diffusion, phonon echoes, and saturation recovery in glasses at low temperatures, Physical Review B, vol.16, issue.6, p.2879, 1977.
DOI : 10.1103/PhysRevB.16.2879

A. L. Burin, Y. Kagan, L. A. Maksimov, and I. Y. Polishchuk, Dephasing Rate in Dielectric Glasses at Ultralow Temperatures, Physical Review Letters, vol.80, issue.13, p.2945, 1998.
DOI : 10.1103/PhysRevLett.80.2945

=. With-?2 and /. , 0 ) tanh ? 2k B T , the domain ?1 > ?2 is found as follows : i) if ? < ? 2kBT , this amounts to ?0 ? ?1/(2?2) ? 2 K, a condition basically always fulfilled since ?0,max is hardly above this energy scale; ii) if ? > 2kBT , one gets ?? 2 0 < ?1T /?2 which amounts either to ?0 ? e1, ?1T /?2) 1/3 in the case where ? < e1,2, or to ?0 ? ?1T /(?2?) in the case where ? > e1,2. Combining these conditions yields the upper curve of the inset of Fig

J. E. Graebner and B. Golding, Phonon echoes in a glass at low temperatures, Physical Review B, vol.19, issue.2, p.964, 1979.
DOI : 10.1103/PhysRevB.19.964

A. L. Burin, Dipole gap effects in low energy excitation spectrum of amorphous solids. Theory for dielectric relaxation, Journal of Low Temperature Physics, vol.70, issue.196, p.309, 1995.
DOI : 10.1007/BF00751512

G. Frossati, J. G. Le, W. Gilchrist, and . Meyer, C: Solid State Phys, J. Phys, vol.10, p.515, 1977.

A. J. Leggett, S. Chakravarty, A. T. Dorsey, M. P. Fisher, A. Garg et al., Dynamics of the dissipative two-state system, Reviews of Modern Physics, vol.59, issue.1, p.1, 1987.
DOI : 10.1103/RevModPhys.59.1

R. G. Devoe and R. G. Brewer, Experimental Test of the Optical Bloch Equations for Solids, Physical Review Letters, vol.50, issue.17, p.1269, 1983.
DOI : 10.1103/PhysRevLett.50.1269

E. Geva and R. Kosloff, On the relaxation of a two???level system driven by a strong electromagnetic field, The Journal of Chemical Physics, vol.102, issue.21, p.8541, 1995.
DOI : 10.1063/1.468844

K. W. `-odkiewicz and J. H. Eberly, Random-telegraph-signal theory of optical resonance relaxation with applications to free induction decay, Physical Review A, vol.32, issue.2, p.992, 1985.
DOI : 10.1103/PhysRevA.32.992

M. Devaud and J. Prieur, Acoustic Hole Burning Experiment in an Amorphous Compound: A Check of the Yamanoi and Eberly Theory, Europhysics Letters (EPL), vol.6, issue.6, p.523, 1988.
DOI : 10.1209/0295-5075/6/6/009

A. Wurger, From coherent tunneling to relaxation, dissipative quantum dynamics of interacting defects, 1997.

S. Rogge, D. Natelson, and D. D. Osheroff, Nonequilibrium and hysteretic low temperature dielectric response to strain in glasses, Journal of Low Temperature Physics, vol.46, issue.5-6, p.717, 1997.
DOI : 10.1007/BF02395933