On the Description of Quantum Dissipative Processes

C. Syris

Hans Cruz-Prado, Alessandro Bravetti, Angel García-Chung

Starting from the geometric description of quantum systems, we propose a novel approach to time-independent dissipative quantum processes according to which energy is dissipated but the coherence of the states is preserved. Our proposal consists of extending the standard symplectic picture of quantum mechanics to a contact manifold and then obtaining dissipation by using appropriate contact Hamiltonian dynamics. We work out the case of finite-level systems for which it is shown, by means of the corresponding contact master equation, that the resulting dynamics constitute a viable alternative candidate for the description of this subclass of dissipative quantum systems. As a concrete application, motivated by recent experimental observations, we describe quantum decays in a 2-level system as coherent and continuous processes.

Ilya Prigogine

A. V. Pakhomov

We develop a theoretical approach for the full analytical description of dissipative optical solitons, which takes into account all relaxation processes in the medium. Most analytical solutions available today for ultrashort optical solitons are obtained upon neglecting a number of relaxation terms in the governing equations for the medium response. The suggested method is based on finding explicit analytical expressions for the extended soliton tails distant enough from the soliton central part, when taking into consideration all relaxation processes. These soliton tails can be described by the linearized equations for the medium response both at the soliton leading and trailing edges. Afterwards, the analytical expressions for the soliton tails and its central part can be matched to yield the full analytical description of ultrashort dissipative solitons with all relaxation processes in the resonant medium properly treated. The proposed approach is demonstrated for ultrashort dissipative solitons in a resonant medium consisting either of only amplifying resonant two-level centers or of a mixture of amplifying and absorbing two-level centers.

P. Caldirola, E. Montaldi

V. Yu. Mylnikov, S. O. Potashin, Alex Kamenev

We study the quantum dynamics of a single bosonic cavity subject to two-photon driving and two-photon dissipation in the presence of finite detuning. Exploiting a hidden time-reversal symmetry, the Wigner representation and the WKB method, we introduce an effective phase-space potential for description of the steady state. It reveals two attracting points, which are metastable due to quantum fluctuations. By employing the Keldysh real-time path integral formalism, we compute the instanton trajectory governing the quantum activation process between these attractors and establish a fundamental connection with the Wigner representation. This relation unifies the steady-state phase-space description with dynamical quantum activation processes. We also derive an analytical expression for the decoherence rate of the system. Our work provides a coherent theoretical framework for analyzing quantum bistability, metastability, and decoherence in driven-dissipative nonlinear resonators, with direct implications for the design of bosonic qubits and quantum information processing.