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Hauptverfasser: White, Christopher David, Winer, Michael, Bernstein, Noam
Format: Preprint
Veröffentlicht: 2026
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Online-Zugang:https://arxiv.org/abs/2601.18869
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author White, Christopher David
Winer, Michael
Bernstein, Noam
author_facet White, Christopher David
Winer, Michael
Bernstein, Noam
contents Random quantum states drawn from the Haar ensemble with a constraint on the energy expectation value $E_{\mathrm{av}} = \langle ψ| H | ψ\rangle$ display \textit{eigenstate condensation}: for $E_{\mathrm{av}}$ below a critical value $E_c$, they develop macroscopic overlap with the ground state. We study eigenstate condensation in systems with finite-dimensional Hilbert spaces. These systems display three phases: a ground-state phase, in which energy-constrained random states have macroscopic overlap with the ground state; a high-temperature phase, in which they have exponentially small overlap with each energy eigenstate; and an anti-ground-state phase, in which they have macroscopic overlap with the most highly excited state. In local spin systems the ground-state and anti-ground-state phases approach the middle of the spectrum as $1/[\text{system size}]$, but -- because the condensation phase transitions have exponential, rather than polynomial, finite-size scaling -- the crossover becomes exponentially sharp in system size and the high-temperature phase is best understood as an extended phase.
format Preprint
id arxiv_https___arxiv_org_abs_2601_18869
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Eigenstate condensation in quantum systems with finite-dimensional Hilbert spaces
White, Christopher David
Winer, Michael
Bernstein, Noam
Quantum Physics
Disordered Systems and Neural Networks
Statistical Mechanics
Strongly Correlated Electrons
Random quantum states drawn from the Haar ensemble with a constraint on the energy expectation value $E_{\mathrm{av}} = \langle ψ| H | ψ\rangle$ display \textit{eigenstate condensation}: for $E_{\mathrm{av}}$ below a critical value $E_c$, they develop macroscopic overlap with the ground state. We study eigenstate condensation in systems with finite-dimensional Hilbert spaces. These systems display three phases: a ground-state phase, in which energy-constrained random states have macroscopic overlap with the ground state; a high-temperature phase, in which they have exponentially small overlap with each energy eigenstate; and an anti-ground-state phase, in which they have macroscopic overlap with the most highly excited state. In local spin systems the ground-state and anti-ground-state phases approach the middle of the spectrum as $1/[\text{system size}]$, but -- because the condensation phase transitions have exponential, rather than polynomial, finite-size scaling -- the crossover becomes exponentially sharp in system size and the high-temperature phase is best understood as an extended phase.
title Eigenstate condensation in quantum systems with finite-dimensional Hilbert spaces
topic Quantum Physics
Disordered Systems and Neural Networks
Statistical Mechanics
Strongly Correlated Electrons
url https://arxiv.org/abs/2601.18869