Bound eigenstates and generalized eigenstates (scattering eigenstates) are two kinds of eigenstates in quantum mechanics. In this work, we first introduce a systematic way to regularize a generalized eigenstates by using the Wick rotation. The states that can be regularized are, in fact, Gamow states since they form poles in the scattering matrix but not localized before the Wick rotation. We then demonstrate an example where a bosonic field interacting with an array of two level systems can have Gamow states with positive real eigenenergies, and the scattering spectrum diverges at the eigenenergy. Since the eigenenergies of this kind locate in a real continuous scattering spectrum, from the scattering matrix point of view, these states resemble the bound states in the continuum (BIC). Unlike BIC, however, these states are non-localized in space and possess the frequency-filtering nature which may lead to potential applications in tunable quantum frequency filters for scattering states.
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Philos Trans A Math Phys Eng Sci
December 2024
School of Science, Centre for Quantum Dynamics, Griffith University, Nathan, Australia.
We place Loudon's quantum treatment of optical phase in in its historical context, and outline research that it inspired. We show how it led Pegg and Barnett to their quantum phase formalism, explaining the challenges that they overcame to define phase operators and phase eigenstates rigorously. We show how the formalism essentially constructs an extended rigged Hilbert space that supports strong limits of the phase operators and includes their eigenstates.
View Article and Find Full Text PDFPhys Rev Lett
December 2024
Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748 Garching, Germany.
We introduce protocols to prepare many-body quantum states with quantum circuits assisted by local operations and classical communication. We show that by lifting the requirement of exact preparation, one can substantially save resources. In particular, the so-called W and, more generally, Dicke states require a circuit depth and number of ancillas per site that are independent of the system size.
View Article and Find Full Text PDFPhys Rev Lett
November 2024
Department of Physics, National University of Singapore, Singapore 117542, Singapore.
In contrast with extended Bloch waves, a single particle can become spatially localized due to the so-called skin effect originating from non-Hermitian pumping. Here we show that in kinetically constrained many-body systems, the skin effect can instead manifest as dynamical amplification within the Fock space, beyond the intuitively expected and previously studied particle localization and clustering. We exemplify this non-Hermitian Fock skin effect in an asymmetric version of the PXP model and show that it gives rise to ergodicity-breaking eigenstates-the non-Hermitian analogs of quantum many-body scars.
View Article and Find Full Text PDFNanophotonics
February 2024
Department of Physics and Center for Optoelectronics and Photonics Paderborn (CeOPP), Paderborn University, 33098 Paderborn, Germany.
Entropy (Basel)
November 2024
Departamento de Física Teórica, Atómica y Óptica, Universidad de Valladolid, 47011 Valladolid, Spain.
Quantum information scrambling refers to the spread of the initially stored information over many degrees of freedom of a quantum many-body system. Information scrambling is intimately linked to the thermalization of isolated quantum many-body systems, and has been typically studied in a sudden quench scenario. Here, we extend the notion of quantum information scrambling to critical quantum many-body systems undergoing an adiabatic evolution.
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