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Non-equilibrium quantum transport is crucial to technological advances ranging from nanoelectronics to thermal management. In essence, it deals with the coherent transfer of energy and (quasi-)particles through quantum channels between…

We present a theory of radio-frequency spectroscopy of impurities interacting with a quantum gas at finite temperature. By working in the canonical ensemble of a single impurity, we show that the impurity spectral response is directly…

Quantum Gases · Physics 2020-08-12 Weizhe Edward Liu , Zhe-Yu Shi , Meera M. Parish , Jesper Levinsen

The decay of an unstable system is usually described by an exponential law. Quantum mechanics predicts strong deviations of the survival probability from the exponential: indeed, the decay is initially quadratic, while at very large times…

Spontaneous decay of a single photon is a notoriously inefficient process in nature irrespective of the frequency range. We report that a quantum phase-slip fluctuation in high-impedance superconducting waveguides can split a single…

We study the behavior of the entropy of the pseudogap Bose-Fermi Kondo model within a dynamical large-$N$ limit, where $N$ is related to the symmetry group of the model. This model is a general quantum impurity model that describes a…

Strongly Correlated Electrons · Physics 2020-09-16 Zuodong Yu , Farzaneh Zamani , Pedro Ribeiro , Stefan Kirchner

The longitudinal coupling of a system to the bath usually induces the pure dephasing of the system. In this paper, we study the collective dephasing induced dissipation and decoherence in a coupled-qubit system with a common bath. It is…

Quantum Physics · Physics 2015-06-22 Z. H. Wang , Y. J. Ji , Yong Li , D. L. Zhou

We shall revisit the conventional adiabatic or Markov approximation, which --contrary to the semiclassical case-- does not preserve the positive-definite character of the corresponding density matrix, thus leading to highly non-physical…

Quantum Physics · Physics 2015-05-13 David Taj , Rita Claudia Iotti , Fausto Rossi

Fermi's Golden Rule (FGR) is one of the most impactful formulas in quantum mechanics, providing a link between easy-to-measure observables - such as transition rates - and fundamental microscopic properties - such as density of states or…

Decoherence of a quantum state coupled to an exterior environment is at the foundation of our understanding of the emergence of classical behavior from the quantum world, but how does it emerge in a finite closed quantum system? Here this…

Quantum Physics · Physics 2015-06-16 O. Fialko

A simple quantum mechanical model consisting of a discrete level resonantly coupled to a continuum of finite width, where the coupling can be varied from perturbative to strong (Fano-Anderson model), is considered. The particle is initially…

Quantum Physics · Physics 2019-02-19 E. Kogan

The Fermi-polaron problem of a mobile impurity interacting with fermionic medium emerges in various contexts, ranging from the foundations of Landau's Fermi-liquid theory to electron-exciton interaction in semiconductors, to unusual…

Quantum Gases · Physics 2021-11-02 Pavel E. Dolgirev , Yi-Fan Qu , Mikhail B. Zvonarev , Tao Shi , Eugene Demler

Fermi's golden rule is of great importance in quantum dynamics. However, in many textbooks on quantum mechanics, its contents and limitations are obscured by the approximations and arguments in the derivation, which are inevitable because…

Quantum Physics · Physics 2016-10-07 J. M. Zhang , Y. Liu

We investigate quantum impurity problems, where a local magnetic moment is coupled to the spin density of a bosonic environment, leading to bosonic versions of the standard Kondo and Anderson impurity models. In a physical situation, these…

Strongly Correlated Electrons · Physics 2008-11-26 Serge Florens , Lars Fritz , Matthias Vojta

Circuit quantum electrodynamics is one of the most promising platforms for efficient quantum simulation and computation. In recent groundbreaking experiments, the immense flexibility of superconducting microwave resonators was utilized to…

We demonstrate the controlled generation of Fock states with up to 15 photons in a microwave coplanar waveguide resonator coupled to a superconducting phase qubit. The subsequent decay of the Fock states, due to dissipation, is then…

Mesoscale and Nanoscale Physics · Physics 2010-11-15 H. Wang , M. Hofheinz , M. Ansmann , R. C. Bialczak , E. Lucero , M. Neeley , A. D. O'Connell , D. Sank , J. Wenner , A. N. Cleland , John M. Martinis

We revisit the physics of a Kondo impurity coupled to a fermionic host with a diverging power-law density of states near the Fermi level, $\rho(\omega) \sim |\omega|^r$, with exponent $-1<r<0$. Using the analytical understanding of several…

Strongly Correlated Electrons · Physics 2013-11-13 Andrew K. Mitchell , Matthias Vojta , Ralf Bulla , Lars Fritz

We theoretically investigate the pure dephasing dynamics of two static impurity qubits embedded within a common environment of ultracold fermionic atoms, which are confined to one spatial dimension. Our goal is to understand how…

Quantum Gases · Physics 2024-02-13 Sindre Brattegard , Mark T. Mitchison

We present a general variational principle for the dynamics of impurity particles immersed in a quantum-mechanical medium. By working within the Heisenberg picture and constructing approximate time-dependent impurity operators, we can take…

Quantum Gases · Physics 2019-05-29 Weizhe Edward Liu , Jesper Levinsen , Meera M. Parish

A quantum system weakly interacting with a fast environment usually undergoes a relaxation with complex frequencies whose imaginary parts are damping rates quadratic in the coupling to the environment, in accord with Fermi's ``Golden…

Quantum Physics · Physics 2009-11-11 Massimiliano Esposito , Fritz Haake

We disentangle all the individual degrees of freedom in the quantum impurity problem to deconstruct the Kondo singlet, both in real and energy space, by studying the contribution of each individual free electron eigenstate. This is a…

Strongly Correlated Electrons · Physics 2017-03-08 Chun Yang , Adrian E. Feiguin