Quantum many-body systems are characterized by their correlations. While equal-time correlators and unequal-time commutators between operators are standard observables, the direct access to unequal-time anti-commutators poses a formidable experimental challenge. Here, we propose a general technique for measuring unequal-time anti-commutators using the linear response of a system to a non-Hermitian perturbation. We illustrate the protocol at the example of a Bose-Hubbard model, where the approach to thermal equilibrium in a closed quantum system can be tracked by measuring both sides of the fluctuation-dissipation relation. We relate the scheme to the quantum Zeno effect and weak measurements, and illustrate possible implementations at the example of a cold-atom system. Our proposal provides a way of characterizing dynamical correlations in quantum many-body systems with potential applications in understanding strongly correlated matter as well as for novel quantum technologies.

From non-Hermitian linear response to dynamical correlations and fluctuation-dissipation relations in quantum many-body systems / Geier, Kevin T.; Hauke, Philipp. - In: PRX QUANTUM. - ISSN 2691-3399. - ELETTRONICO. - 3:3(2022), p. 030308. [10.1103/PRXQuantum.3.030308]

From non-Hermitian linear response to dynamical correlations and fluctuation-dissipation relations in quantum many-body systems

Geier, Kevin T.
Primo
;
Hauke, Philipp
Ultimo
2022-01-01

Abstract

Quantum many-body systems are characterized by their correlations. While equal-time correlators and unequal-time commutators between operators are standard observables, the direct access to unequal-time anti-commutators poses a formidable experimental challenge. Here, we propose a general technique for measuring unequal-time anti-commutators using the linear response of a system to a non-Hermitian perturbation. We illustrate the protocol at the example of a Bose-Hubbard model, where the approach to thermal equilibrium in a closed quantum system can be tracked by measuring both sides of the fluctuation-dissipation relation. We relate the scheme to the quantum Zeno effect and weak measurements, and illustrate possible implementations at the example of a cold-atom system. Our proposal provides a way of characterizing dynamical correlations in quantum many-body systems with potential applications in understanding strongly correlated matter as well as for novel quantum technologies.
2022
3
Geier, Kevin T.; Hauke, Philipp
From non-Hermitian linear response to dynamical correlations and fluctuation-dissipation relations in quantum many-body systems / Geier, Kevin T.; Hauke, Philipp. - In: PRX QUANTUM. - ISSN 2691-3399. - ELETTRONICO. - 3:3(2022), p. 030308. [10.1103/PRXQuantum.3.030308]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11572/304101
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