Fundamental decoherence in quantum gravity

Abstract

A recently introduced discrete formalism allows to solve the problem of time in quantum gravity in a relational manner. Quantum mechanics formulated with a relational time is not exactly unitary and implies a fundamental mechanism for decoherence of quantum states. The mechanism is strong enough to render the black hole information puzzle unobservable.

Classical and Quantum General Relativity: A New Paradigm

“…The more qubits in the computer, the "more macroscopic" its quantum states are and the larger the loss of coherence. We have estimated [16] that the maximum number of operations (parallel or serial) that a quantum computer of L qubits of size R can carry out is n ≤ The fundamental loss of coherence can yield the black hole information paradox invisible [17]. As we argued quantum states lose coherence naturally, albeit at a very small rate.…”

Fundamental decoherence from quantum gravity: a pedagogical review

“…Of course, a full calculation of the evaporation of a black hole would require a detailed modelling including quantum effects of gravity that no one is in a position of carrying out yet. We have done a naive estimate [3,15] of how our effect would take place in the case of an evaporating black hole. To this aim we have assumed the black hole is a system with energy levels (this is a common assumption in many quantum gravity scenarios), and that most of the Hawking radiation is coming from a transition between two dominant energy levels separated by a characteristic frequency dependent on the temperature as…”

“…Although we have discussed several of these issues in previous papers [1,2,3], the latter were written with an audience of relativists and quantum gravity experts in mind, and involving a particular approach to quantum gravity we have been pioneering [4,5]. Since many of the results are really robust and independent of details of quantum gravity, we are giving a presentation in this paper with minimal references to issues that may be unfamiliar to physicists from outside the research area of gravitational physics.…”

Introduction to Quantum-Gravity Phenomenology

“…Moreover, perhaps most importantly, some recent studies [78] invite us to consider the possibility that in the same contexts in which Loop-Quantum-Gravity departures from Lorentz symmetry may be revealed one should also adopt a density-matrix formalism, and then the whole picture might reduce to the familiar Lorentz-invariant quantumfield-theory description in contexts involving both relatively low energies and relatively low boosts with respect to the center-of-mass frame. We should therefore be prepared for surprises in the description of dynamics.…”

“…And on the basis of the recent results of Ref. [78] it appears plausible that in several contexts in which one would naively expect a low-energy field theory description Loop Quantum Gravity might instead require a density-matrix description.…”