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Quantum-Zeno Fermi polaron in the strong dissipation limit

Wasak , T., Richard Schmidt, Piazza, F.

Published Jan 1, 2021• 18 citations
OpenAlex

Abstract

The interplay between measurement and quantum correlations in many-body systems can lead to novel types of collective phenomena which are not accessible in isolated systems. In this work, we merge the Zeno paradigm of quantum measurement theory with the concept of polarons in condensed-matter physics. The resulting quantum-Zeno Fermi polaron is a quasiparticle which emerges for lossy impurities interacting with a quantum-degenerate bath of fermions. For loss rates of the order of the impurity-fermion binding energy, the quasiparticle is short lived. However, we show that in the strongly dissipative regime of large loss rates a long-lived polaron branch reemerges. This quantum-Zeno Fermi polaron originates from the nontrivial interplay between the Fermi surface and the surface of the momentum region forbidden by the quantum-Zeno projection. The situation we consider here is realized naturally for polaritonic impurities in charge-tunable semiconductors and can be also implemented using dressed atomic states in ultracold gases.

Related papers

Quantum-Zeno Fermi polaron in the strong dissipation limit

Tomasz Wasak, Richard Schmidt, Francesco Piazza

The interplay between measurement and quantum correlations in many-body systems can lead to novel types of collective phenomena which are not accessible in isolated systems.In this work, we merge the Zeno paradigm of quantum measurement theory with the concept of polarons in condensed-matter physics.The resulting quantum-Zeno Fermi polaron is a quasiparticle which emerges for lossy impurities interacting with a quantum-degenerate bath of fermions.For loss rates of the order of the impurity-fermion binding energy, the quasiparticle is short lived.However, we show that in the strongly dissipative regime of large loss rates a long-lived polaron branch reemerges.This quantum-Zeno Fermi polaron originates from the nontrivial interplay between the Fermi surface and the surface of the momentum region forbidden by the quantum-Zeno projection.The situation we consider here is realized naturally for polaritonic impurities in charge-tunable semiconductors and can be also implemented using dressed atomic states in ultracold gases.

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The study of polaron of an open quantum system plays an important role in both verifying the effectiveness of approximate many-body theory and predicting novel quantum phenomenone in open quantum systems. In a pioneering work, Piazza et al have proposed a Fermi-polaron scheme with a lossy impurity [54], which exhibits a novel long-lived attractive polaron branch in the quantum Zeno limit. However, we would also run into a counterpart problem that an impurity scatters with an open quantum bath exciting polarons, which is what we focus in on. In this work, we conclude the molecular state under the two limits of vanishing small and infinite large dissipation intensity as well as the reason why the dissipation range leads to the decrease of the gap between the molecular state and molecule-hole continuum in the former case by means of analytically research. The spectrum functions of molecular and polaron states with different dissipation range and loss rate are investigated. We find the spectral signals of molecular and polaron states will both diffuse firstly and then revives as the dissipation is on the raise. Moreover, it is shown that the attractive and repulsive polarons show different response to the increasing dissipation range in our model. At last, we exhibit the polaron energy, residue, effective mass and two-body decay for mass balanced and imbalanced systems. Our results might be useful for future cold atom experiment on open quantum systems.

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Understanding how strong correlations and dissipation combine to shape collective quantum excitations is a central challenge in many-body physics. We investigate the effect of dissipative light-matter coupling on strongly interacting exciton-polaritons in the presence of a biexciton resonance, which gives rise to polaron-polariton quasiparticles. We show that the interplay between many-body correlations and non-Hermitian coupling generates anomalous dispersion relations and exceptional points in the polaron-polariton spectrum. The location and coexistence of exceptional points are controlled by the dissipative coupling and the relative decay rates of the excitonic and photonic constituents, allowing them to emerge across different polaron-polariton branches. These results identify dissipative polaron-polaritons as a versatile platform for exploring non-Hermitian many-body physics with tunable light-matter quasiparticles.

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Quasiparticles are emergent excitations of matter that underlie much of our understanding of quantum many-body systems. Therefore, the prospect of controlling their properties has both fundamental and practical implications. However, in solid-state materials, it is often challenging to understand how quasiparticles are modified by external fields due to their complex interplay with other collective excitations. Here we demonstrate the manipulation of Fermi polarons—quasiparticles formed by impurities interacting with a Fermi gas—in a homogeneous atomic gas using fast radio-frequency control. Exploiting two internal states of the impurity species, we develop a steady-state spectroscopy, from which we extract the energy of the driven polaron. By varying the drive Rabi frequency, we measure the decay rate and the quasiparticle residue of the polaron in the weak-drive limit. At large Rabi frequencies, we observe signs that the drive causes a hybridization of the driven polaron with an incoherent background, leading to the breakdown of a description in terms of textbook quasiparticles. Our experiment establishes the driven Fermi polaron as a promising platform for studying controllable quasiparticles in strongly driven quantum matter and calls for a controlled theoretical framework to describe the dynamics of this strongly interacting quantum system. Fermi polarons are quasiparticles formed by impurities immersed in a Fermi gas. An experiment in an ultracold fermionic gas now shows how to control their properties with a tunable radio-frequency field.

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Ultracold quantum wires with localized losses: Many-body quantum Zeno effect

Heinrich Fröml, Christopher Muckel, Corinna Kollath +2 more

The effect of localized loss on a one-dimensional gas of interacting fermions is investigated. Here, the interplay of gapless quantum fluctuations and particle interactions strongly renormalizes the dissipative impurity. As a result, the loss probability for modes close to the Fermi energy vanishes for arbitrary strength of the dissipation, as a many-body incarnation of the quantum Zeno effect. This is reflected in the shape of the particle momentum distribution, exhibiting a peak close to the Fermi momentum.

arXiv:1910.10741•Physical review. B./Physical review. B•Apr 1, 2020•75 citations
The interplay between measurement and quantum correlations in many-body systems can lead to novel types of collective phenomena which are not accessible in isolated systems. In this work, we merge the Zeno paradigm of quantum measurement theory with the concept of polarons in condensed-matter physics. The resulting quantum-Zeno Fermi polaron is a quasiparticle which emerges for lossy impurities interacting with a quantum-degenerate bath of fermions. For loss rates of the order of the impurity-fermion binding energy, the quasiparticle is short lived. However, we show that in the strongly dissipative regime of large loss rates a long-lived polaron branch reemerges. This quantum-Zeno Fermi polaron originates from the nontrivial interplay between the Fermi surface and the surface of the momentum region forbidden by the quantum-Zeno projection. The situation we consider here is realized naturally for polaritonic impurities in charge-tunable semiconductors and can be also implemented using dressed atomic states in ultracold gases.
The interplay between measurement and quantum correlations in many-body systems can lead to novel types of collective phenomena which are not accessible in isolated systems.In this work, we merge the Zeno paradigm of quantum measurement theory with the concept of polarons in condensed-matter physics.The resulting quantum-Zeno Fermi polaron is a quasiparticle which emerges for lossy impurities interacting with a quantum-degenerate bath of fermions.For loss rates of the order of the impurity-fermion binding energy, the quasiparticle is short lived.However, we show that in the strongly dissipative regime of large loss rates a long-lived polaron branch reemerges.This quantum-Zeno Fermi polaron originates from the nontrivial interplay between the Fermi surface and the surface of the momentum region forbidden by the quantum-Zeno projection.The situation we consider here is realized naturally for polaritonic impurities in charge-tunable semiconductors and can be also implemented using dressed atomic states in ultracold gases.
The study of polaron of an open quantum system plays an important role in both verifying the effectiveness of approximate many-body theory and predicting novel quantum phenomenone in open quantum systems. In a pioneering work, Piazza et al have proposed a Fermi-polaron scheme with a lossy impurity [54], which exhibits a novel long-lived attractive polaron branch in the quantum Zeno limit. However, we would also run into a counterpart problem that an impurity scatters with an open quantum bath exciting polarons, which is what we focus in on. In this work, we conclude the molecular state under the two limits of vanishing small and infinite large dissipation intensity as well as the reason why the dissipation range leads to the decrease of the gap between the molecular state and molecule-hole continuum in the former case by means of analytically research. The spectrum functions of molecular and polaron states with different dissipation range and loss rate are investigated. We find the spectral signals of molecular and polaron states will both diffuse firstly and then revives as the dissipation is on the raise. Moreover, it is shown that the attractive and repulsive polarons show different response to the increasing dissipation range in our model. At last, we exhibit the polaron energy, residue, effective mass and two-body decay for mass balanced and imbalanced systems. Our results might be useful for future cold atom experiment on open quantum systems.
Understanding how strong correlations and dissipation combine to shape collective quantum excitations is a central challenge in many-body physics. We investigate the effect of dissipative light-matter coupling on strongly interacting exciton-polaritons in the presence of a biexciton resonance, which gives rise to polaron-polariton quasiparticles. We show that the interplay between many-body correlations and non-Hermitian coupling generates anomalous dispersion relations and exceptional points in the polaron-polariton spectrum. The location and coexistence of exceptional points are controlled by the dissipative coupling and the relative decay rates of the excitonic and photonic constituents, allowing them to emerge across different polaron-polariton branches. These results identify dissipative polaron-polaritons as a versatile platform for exploring non-Hermitian many-body physics with tunable light-matter quasiparticles.
Quasiparticles are emergent excitations of matter that underlie much of our understanding of quantum many-body systems. Therefore, the prospect of controlling their properties has both fundamental and practical implications. However, in solid-state materials, it is often challenging to understand how quasiparticles are modified by external fields due to their complex interplay with other collective excitations. Here we demonstrate the manipulation of Fermi polarons—quasiparticles formed by impurities interacting with a Fermi gas—in a homogeneous atomic gas using fast radio-frequency control. Exploiting two internal states of the impurity species, we develop a steady-state spectroscopy, from which we extract the energy of the driven polaron. By varying the drive Rabi frequency, we measure the decay rate and the quasiparticle residue of the polaron in the weak-drive limit. At large Rabi frequencies, we observe signs that the drive causes a hybridization of the driven polaron with an incoherent background, leading to the breakdown of a description in terms of textbook quasiparticles. Our experiment establishes the driven Fermi polaron as a promising platform for studying controllable quasiparticles in strongly driven quantum matter and calls for a controlled theoretical framework to describe the dynamics of this strongly interacting quantum system. Fermi polarons are quasiparticles formed by impurities immersed in a Fermi gas. An experiment in an ultracold fermionic gas now shows how to control their properties with a tunable radio-frequency field.
Polaron quasiparticles are formed when a mobile impurity is coupled to the elementary excitations of a many-particle background. In the field of ultracold atoms, the study of the associated impurity problem has attracted a growing interest over the last fifteen years. Polaron quasiparticle properties are essential to our understanding of a variety of paradigmatic quantum many-body systems realized in ultracold atomic gases and in the solid state, from imbalanced Bose–Fermi and Fermi–Fermi mixtures to fermionic Hubbard models. In this topical review, we focus on the so-called repulsive polaron branch, which emerges as an excited many-body state in systems with underlying attractive interactions such as ultracold atomic mixtures, and is characterized by an effective repulsion between the impurity and the surrounding medium. We give a brief account of the current theoretical and experimental understanding of repulsive polaron properties, for impurities embedded in both fermionic and bosonic media, and we highlight open issues deserving future investigations.
The effect of localized loss on a one-dimensional gas of interacting fermions is investigated. Here, the interplay of gapless quantum fluctuations and particle interactions strongly renormalizes the dissipative impurity. As a result, the loss probability for modes close to the Fermi energy vanishes for arbitrary strength of the dissipation, as a many-body incarnation of the quantum Zeno effect. This is reflected in the shape of the particle momentum distribution, exhibiting a peak close to the Fermi momentum.