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The pigeonhole principle: "If you put three pigeons in two pigeonholes, at least two of the pigeons end up in the same hole," is an obvious yet fundamental principle of nature as it captures the very essence of counting. Here however we show that in quantum mechanics this is not true! We find instances when three quantum particles are put in two boxes, yet no two particles are in the same box. Furthermore, we show that the above "quantum pigeonhole principle" is only one of a host of related quantum effects, and points to a very interesting structure of quantum mechanics that was hitherto unnoticed. Our results shed new light on the very notions of separability and correlations in quantum mechanics and on the nature of interactions. It also presents a new role for entanglement, complementary to the usual one. Finally, interferometric experiments that illustrate our effects are proposed.
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http://dx.doi.org/10.1073/pnas.1522411112 | DOI Listing |
J Chem Inf Model
September 2025
Department of Chemistry, Delaware State University, Dover, Delaware 19901, United States.
The calculation of the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap for chemical molecules is computationally intensive using quantum mechanics (QM) methods, while experimental determination is often costly and time-consuming. Machine Learning (ML) offers a cost-effective and rapid alternative, enabling efficient predictions of HOMO-LUMO gap values across large data sets without the need for extensive QM computations or experiments. ML models facilitate the screening of diverse molecules, providing valuable insights into complex chemical spaces and integrating seamlessly into high-throughput workflows to prioritize candidates for experimental validation.
View Article and Find Full Text PDFJ Chem Theory Comput
September 2025
Materials DX Research Center, National Institute of Advanced Industrial Science and Technology, Tsukuba Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan.
The quantum mechanics/molecular mechanics (QM/MM) method is a powerful approach for investigating solid surfaces in contact with various types of media, since it allows for flexible modeling of complex interfaces while maintaining an all-atom representation. The mean-field QM/MM method is an average reaction field model within the QM/MM framework. The method addresses the challenges associated with the statistical sampling of interfacial atomic configurations of a medium and enables efficient calculation of free energies.
View Article and Find Full Text PDFPhys Rev Lett
August 2025
East China Normal University, Key Laboratory of Polar Materials and Devices (MOE), School of Physics and Electronic Science, Shanghai 200241, China.
The far-from-equilibrium dynamics of certain interacting quantum systems still defy precise understanding. One example is the so-called quantum many-body scars (QMBSs), where a set of energy eigenstates evade thermalization to give rise to long-lived oscillations. Despite the success of viewing scars from the perspectives of symmetry, commutant algebra, and quasiparticles, it remains a challenge to elucidate the mechanism underlying all QMBS and to distinguish them from other forms of ergodicity breaking.
View Article and Find Full Text PDFPhys Rev Lett
August 2025
University of Ljubljana, Department of Physics, Faculty of Mathematics and Physics, Jadranska 19, SI-1000 Ljubljana, Slovenia.
We propose a spatially inhomogeneous matrix product Ansatz for an exact many-body density operator of a boundary-driven XXZ quantum circuit. The Ansatz has formally infinite bond dimension and is fundamentally different from previous constructions. The circuit is driven by a pair of reset quantum channels applied on the boundary qubits, which polarize the qubits to arbitrary pure target states.
View Article and Find Full Text PDFJ Chem Theory Comput
September 2025
Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 17, 1090 Vienna, Austria.
We present a novel, flexible framework for electronic structure interfaces designed for nonadiabatic dynamics simulations, implemented in Python 3 using concepts of object-oriented programming. This framework streamlines the development of new interfaces by providing a reusable and extendable code base. It supports the computation of energies, gradients, various couplings─like spin-orbit couplings, nonadiabatic couplings, and transition dipole moments─and other properties for an arbitrary number of states with any multiplicities and charges.
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