1993-1996 Department of Physics, Imperial College, London, UK
Ph.D. Thesis title: Emergence of Classical Behaviour in Quantum Systems
1992 -1993 Department of Physics, Imperial College, London, UK
M.Sc. on Quantum Fields and Fundamental Forces
1988 - 1992 Department of Physics, University of Patras, Greece
B.Sc. in Physics
84
Scopus Publications
2694
Scholar Citations
29
Scholar h-index
66
Scholar i10-index
Scopus Publications
Towards satellite tests combining general relativity and quantum mechanics through quantum optical interferometry: progress on the deep space quantum link Makan Mohageg, Charis Anastopoulos, Olivia Brasher, Jason Gallicchio, Bei Lok Hu, Thomas Jennewein, Spencer Johnson, Shih-Yuin Lin, Alexander Ling, Alexander Lohrmann, Christoph Marquardt, Luca Mazzarella, Matthias Meister, Raymond Newell, Albert Roura, Giuseppe Vallone, Paolo Villoresi, Lisa Wörner, Paul Kwiat EPJ Quantum Technology, 2025 The Deep Space Quantum Link (DSQL) is a space-mission concept that aims to explore the interplay between general relativity and quantum mechanics using quantum optical interferometry. This mission concept was formally presented to the United States National Academy of Science Decadal Survey as a research campaign for Fundamental Physics in 2022. Since then, advances have been made in the space-based quantum optical technologies required to conduct a DSQL-type mission. In addition, other research efforts have defined alternative measurement concepts to explore the same scientific questions motivating the DSQL mission. This paper serves as an update to the community on the status of the DSQL mission concept and related research and technology development efforts.
Relativistic quantum information measures from unequal-time QFT correlation functions Charis Anastopoulos, Konstantina Savvidou Annals of Physics, 2025 This paper continues on the program of developing a relativistic quantum information theory in terms of unequal-time correlation functions in quantum field theory (QFT) (Anastopoulos et al., 2023). Here, we focus on the definition of quantum resources from the irreducibly quantum behavior contained in the correlation functions of a QFT. We explain how set-ups with N particle detectors probe the information in the high order field correlation functions. Our main object is the associated hierarchy of probability densities of N -detector events. We show that classical probabilistic hierarchies are subject to two conditions: Kolmogorov additivity and measurement independence. QFT violates those conditions, and the degree of violation enables us to define novel quantum resources. We give specific examples in set-ups where the main observables are the times of particle detection events. The new resources capture instances of irreducibly quantum behavior that differs from the quantum behavior encapsulated in Bell inequalities. An interesting byproduct of our analysis is a relativistic state reduction rule for particles detected through scattering.
Final states in quantum cosmology: Cosmic acceleration as a quantum postselection effect Charis Anastopoulos Physical Review D, 2025 Standard quantum theory admits naturally statistical ensembles that are both pre-selected and post-selected, i.e., they involve both an initial and a final state. We argue that there is no compelling physical reason to preclude a probability assignment with a final quantum state at the cosmological level. We therefore analyze the implications of a final state in the probability assignment for quantum cosmology. To this end, we derive effective classical equations of motion for systems subject to both initial and final conditions. Remarkably, these effective equations do not depend on the details of the quantum theory, but only on the geometric features of the classical state space. When applied to Friedman-Robertson-Walker cosmological models, these effective equations generically describe cosmic acceleration in the absence of a cosmological constant, dark energy, or modified gravitational dynamics. Therefore, cosmic acceleration emerges as a quantum post-selection effect, that is, a macroscopic quantum phenomenon.
Gravity-mediated decoherence Dimitris Moustos, Charis Anastopoulos Physical Review D, 2024 A small quantum system within the gravitational field of a massive body will be entangled with the quantum degrees of freedom of the latter. Hence, the massive body acts as an environment, and it induces nonunitary dynamics, noise, and decoherence to the quantum system. It is impossible to shield systems on Earth from this gravity-mediated decoherence, which could severely affect all experiments with macroscopic quantum systems. We undertake a first-principles analysis of this effect, by deriving the corresponding open system dynamics. We find that near-future quantum experiments are not affected, but there is a strong decoherence effect at the human scale. The decoherence time for a superposition of two localized states of a human with a one meter separation is of the order of one second.
The Laser Interferometer Space Antenna mission in Greece White Paper Nikolaos Karnesis, Nikolaos Stergioulas, George Pappas, Charis Anastopoulos, John Antoniadis, Theocharis Apostolatos, Spyros Basilakos, Kyriakos Destounis, Eleni Areti, Georgios Lukes-Gerakopoulos, Konstantinos N. Gourgouliatos, Kostas D. Kokkotas, George Kottaras, V. K. Oikonomou, Theodoros Papanikolaou, Leandros Perivolaropoulos, Manolis Plionis, Emmanuel N. Saridakis, Theodoros Sarris, Elias C. Vagenas, Wolf von Klitzing International Journal of Modern Physics D, 2024 The Laser Interferometer Space Antenna (LISA) mission, scheduled for launch in the mid-2030s, is a gravitational wave space observatory designed to detect sources emitting in the millihertz band. LISA is an European Space Agency flagship mission, currently entering the Phase-B development phase. It is expected to help us improve our understanding of our Universe by measuring gravitational wave sources of different types, with some of the sources being at very high redshifts ([Formula: see text]). On February 23, 2022, we organized the first LISA in Greece Workshop. This Workshop aimed to inform the Greek scientific and tech industry communities about the possibilities of participating in LISA science and the LISA mission, with the support of the Hellenic Space Center. In this White Paper, we summarize the outcomes of the Workshop, the most important aspect of it being the inclusion of [Formula: see text] Greek researchers to the LISA Consortium, raising our total number to [Formula: see text]. At the same time, we present a road map with the future steps and actions of the Greek Gravitational Wave community with respect to the LISA mission.
Particle-field duality in QFT measurements Maria Papageorgiou, Jose de Ramón, Charis Anastopoulos Physical Review D, 2024 Pointlike systems coupled to quantum fields are often employed as toy models for measurements in quantum field theory. In this paper, we identify the field observables recorded by such models. We show that in models that work in the strong coupling regime, the apparatus is correlated with smeared field amplitudes, while in models that work in weak coupling the apparatus records particle aspects of the field, such as the existence of a particle-like time of arrival and resonant absorption. Then, we develop an improved field-detector interaction model, adapting the formalism of Quantum Brownian motion, that is exactly solvable. This model confirms the association of field and particle properties in the strong and weak coupling regimes, respectively. Further, it can also describe the intermediate regime, in which the field-particle characteristics `merge'. In contrast to standard perturbation techniques, this model also recovers the relativistic Breit-Wigner resonant behavior in the weak coupling regime. The modulation of field-particle-duality by a single tunable parameter is a novel feature that is, in principle, experimentally accessible.
Quantum Probabilities for the Causal Ordering of Events Charis Anastopoulos, Maria-Electra Plakitsi Dynamics, 2023 We develop a new formalism for constructing probabilities associated with the causal ordering of events in quantum theory, where an event is defined as the emergence of a measurement record on a detector. We start with constructing probabilities for the causal ordering events in classical physics, where events are defined in terms of worldline coincidences. Then, we show how these notions generalize to quantum systems, where there exists no fundamental notion of trajectory. The probabilities constructed here are experimentally accessible, at least in principle. Our analysis here clarifies that the existence of quantum orderings of events do not require quantum gravity effects: it is a consequence of the quantum dynamics of matter, and it appears in the presence of a fixed background spacetime.
Thermodynamics of spherically symmetric thin-shell spacetimes Demetrios Kotopoulis, Charis Anastopoulos Classical and Quantum Gravity, 2023 We analyze the thermodynamics of spherically symmetric thin-shell solutions to Einstein’s equations, including solutions with negative interior mass. We show the inclusion of such solutions is essential for the thermodynamic consistency of the system: the maximum energy principle applies when we include an entropy term from the singularity of the negative-mass solutions, in addition to the Bekenstein–Hawking term for the entropy of solutions with positive interior mass. Then, the thermodynamic analysis leads to four distinct thermodynamic phases. We also show that all types of solutions can be either thermodynamically stable or dynamically stable, but only solutions with zero interior mass can be both. Since most of our results are analytic, thin shell models emerge as a useful theoretical paradigm for exploring gravitational thermodynamics. Our results provide an additional argument in support of the assignment of entropy to the singularity of negative-mass Schwarzschild spacetimes, and, consequently, to Penrose’s conjecture about the assignment of entropy to singularities.
Quantum statistical mechanics near a black hole horizon Eirini Sourtzinou, Charis Anastopoulos Physical Review D, 2023 We undertake a first-principles analysis of the thermodynamics of a small body near a black hole horizon. In particular, we study the paradigmatic system of a quantum ideal gas in a small box hovering over the Schwarzschild horizon. We describe the gas in terms of free quantum fields, bosonic and fermionic, massive and massless. We identify thermodynamic properties through the microcanonical distribution. We first analyse the more general case of a box in Rindler spacetime, and then specialize to the black hole case. The physics depends strongly on the distance of the box from the horizon, which we treat as a macroscopic thermodynamic variable. We find that the effective dimension of the system transitions from three-dimensional to two-dimensional as we approach the horizon, that Bekenstein's bound fails when the box is adiabatically lowered towards the black hole, and that the pressure is highly anisotropic. The pressure difference between the upper and lower wall leads to an effective force that must be added to the gravitational acceleration. We also show that the approximation of quantum fields propagating on a fixed background for matter breaks down when the system is brought to microscopic distances from the horizon, in which case backreaction effects must be included.
The deep space quantum link: prospective fundamental physics experiments using long-baseline quantum optics Makan Mohageg, Luca Mazzarella, Charis Anastopoulos, Jason Gallicchio, Bei-Lok Hu, Thomas Jennewein, Spencer Johnson, Shih-Yuin Lin, Alexander Ling, Christoph Marquardt, Matthias Meister, Raymond Newell, Albert Roura, Wolfgang P. Schleich, Christian Schubert, Dmitry V. Strekalov, Giuseppe Vallone, Paolo Villoresi, Lisa Wörner, Nan Yu, Aileen Zhai, Paul Kwiat EPJ Quantum Technology, 2022
Goals and feasibility of the Deep Space Quantum Link Luca Mazzarella, Makan Mohageg, Dmitry V. Strekalov, Aileen J. Zhai, Ulf E. Israelsson, Andrey Matsko, Nan Yu, Charis Anastopoulos, Bradley Carpenter, Jason R. Gallicchio, Bei-Lok Hu, Thomas Jennewein, Paul Kwiat, Shih-Yuin Lin, Alexander Ling, Christoph Marquardt, Matthias Meister, Brian S. Moffat, Raymond T. Newell, Albert Roura, Christian Schubert, Giuseppe Vallone, Paolo Villoresi, Lisa Woerner Proceedings of SPIE the International Society for Optical Engineering, 2021
PARTICLE OR WAVE: THE EVOLUTION OF THE CONCEPT OF MATTER IN MODERN PHYSICS Particle or Wave the Evolution of the Concept of Matter in Modern Physics, 2020
Singular Solutions of the Tolman Oppenheimer Volkoff Equation with a Cosmological Constant Classification and Properties C Dounis, C Anastopoulos arXiv preprint arXiv:2604.13976 , 2026 2026
Time of arrival on a ring and relativistic quantum clocks I Vakondios, C Anastopoulos arXiv preprint arXiv:2603.27311 , 2026 2026
Quantum field theory measurements for relativistic particles N Koliopoulou, C Anastopoulos, N Savvidou arXiv preprint arXiv:2602.14175 , 2026 2026
Towards satellite tests combining general relativity and quantum mechanics through quantum optical interferometry: progress on the deep space quantum link M Mohageg, C Anastopoulos, O Brasher, J Gallicchio, BL Hu, ... EPJ Quantum Technology 12 (1), 78 , 2025 2025 Citations: 2
Including gravity in equilibrium thermodynamics E Sourtzinou, C Anastopoulos arXiv preprint arXiv:2508.13061 , 2025 2025
Relativistic quantum information measures from unequal-time QFT correlation functions C Anastopoulos, K Savvidou Annals of Physics, 170146 , 2025 2025 Citations: 2
Final states in quantum cosmology: Cosmic acceleration as a quantum postselection effect C Anastopoulos Physical Review D 111 (6), 064045 , 2025 2025 Citations: 3
Gravity-mediated decoherence D Moustos, C Anastopoulos Physical Review D 110 (2), 024022 , 2024 2024 Citations: 3
The laser interferometer space antenna mission in Greece white paper N Karnesis, N Stergioulas, G Pappas, C Anastopoulos, J Antoniadis, ... International Journal of Modern Physics D 33 (07n08), 2450027 , 2024 2024 Citations: 27
Particle-field duality in QFT measurements M Papageorgiou, J de Ramón, C Anastopoulos Physical Review D 109 (6), 065024 , 2024 2024 Citations: 11
Relativistic Time-of-Arrival Measurements: Predictions, Post-Selection and Causality Problems C Anastopoulos, ME Plakitsi Foundations 3 (4), 724-737 , 2023 2023 Citations: 2
Thermodynamics of spherically symmetric thin-shell spacetimes D Kotopoulis, C Anastopoulos Classical and Quantum Gravity 40 (22), 225005 , 2023 2023 Citations: 2
Quantum probabilities for the causal ordering of events C Anastopoulos, ME Plakitsi Dynamics 3 (4), 695-710 , 2023 2023
Quantum theory: a foundational approach C Anastopoulos Cambridge University Press , 2023 2023 Citations: 9
Towards a field-theory based relativistic quantum information C Anastopoulos, BL Hu, K Savvidou Journal of Physics: Conference Series 2533 (1), 012004 , 2023 2023 Citations: 6
Quantum statistical mechanics near a black hole horizon E Sourtzinou, C Anastopoulos Physical Review D 107 (8), 085006 , 2023 2023 Citations: 7
Quantum field theory based quantum information: Measurements and correlations C Anastopoulos, BL Hu, K Savvidou Annals of Physics 450, 169239 , 2023 2023 Citations: 30
The deep space quantum link: prospective fundamental physics experiments using long-baseline quantum optics M Mohageg, L Mazzarella, C Anastopoulos, J Gallicchio, BL Hu, ... EPJ Quantum Technology 9 (1), 25 , 2022 2022 Citations: 69
Gravity, quantum fields and quantum information: Problems with classical channel and stochastic theories C Anastopoulos, BL Hu Entropy 24 (4), 490 , 2022 2022 Citations: 16
Gravitational decoherence: A thematic overview C Anastopoulos, BL Hu AVS Quantum Science 4 (1) , 2022 2022 Citations: 41
MOST CITED SCHOLAR PUBLICATIONS
A master equation for gravitational decoherence: probing the textures of spacetime C Anastopoulos, BL Hu Classical and Quantum Gravity 30 (16), 165007 , 2013 2013 Citations: 186
The rotating-wave approximation: consistency and applicability from an open quantum system analysis C Fleming, NI Cummings, C Anastopoulos, BL Hu Journal of Physics A: Mathematical and Theoretical 43 (40), 405304 , 2010 2010 Citations: 142
Two-level atom-field interaction: Exact master equations for non-Markovian dynamics, decoherence, and relaxation C Anastopoulos, BL Hu Physical Review A 62 (3), 033821 , 2000 2000 Citations: 120
Problems with the Newton–Schrödinger equations C Anastopoulos, BL Hu New Journal of Physics 16 (8), 085007 , 2014 2014 Citations: 101
Generalized uncertainty relations and long-time limits for quantum Brownian motion models C Anastopoulos, JJ Halliwell Physical Review D 51 (12), 6870 , 1995 1995 Citations: 95
Probing a gravitational cat state C Anastopoulos, BL Hu Classical and Quantum Gravity 32 (16), 165022 , 2015 2015 Citations: 91
Quantum superposition of two gravitational cat states C Anastopoulos, BL Hu Classical and Quantum Gravity 37 (23), 235012 , 2020 2020 Citations: 81
Time-of-arrival probabilities and quantum measurements C Anastopoulos, N Savvidou Journal of mathematical physics 47 (12) , 2006 2006 Citations: 79
Non-Markovian qubit dynamics in a thermal field bath: Relaxation, decoherence, and entanglement S Shresta, C Anastopoulos, A Dragulescu, BL Hu Physical Review A—Atomic, Molecular, and Optical Physics 71 (2), 022109 , 2005 2005 Citations: 76
The deep space quantum link: prospective fundamental physics experiments using long-baseline quantum optics M Mohageg, L Mazzarella, C Anastopoulos, J Gallicchio, BL Hu, ... EPJ Quantum Technology 9 (1), 25 , 2022 2022 Citations: 69
Particle or wave: The evolution of the concept of matter in modern physics C Anastopoulos Princeton University Press , 2020 2020 Citations: 68
Non-Markovian time evolution of an accelerated qubit D Moustos, C Anastopoulos Physical Review D 95 (2), 025020 , 2017 2017 Citations: 64
Time-of-arrival probabilities for general particle detectors C Anastopoulos, N Savvidou Arxiv preprint arXiv:1205.2781 , 2012 2012 Citations: 61
Comment on" A Spin Entanglement Witness for Quantum Gravity" and on" Gravitationally Induced Entanglement between Two Massive Particles is Sufficient Evidence of Quantum … C Anastopoulos, BL Hu arXiv preprint arXiv:1804.11315 , 2018 2018 Citations: 58
Equivalence principle for quantum systems: dephasing and phase shift of free-falling particles C Anastopoulos, BL Hu Classical and Quantum Gravity 35 (3), 035011 , 2018 2018 Citations: 58
Quantum theory of nonrelativistic particles interacting with gravity C Anastopoulos Physical Review D 54 (2), 1600 , 1996 1996 Citations: 54
Gravitational effects in macroscopic quantum systems: a first-principles analysis C Anastopoulos, M Lagouvardos, K Savvidou Classical and Quantum Gravity 38 (15), 155012 , 2021 2021 Citations: 46
Non-Markovian entanglement dynamics of two qubits interacting with a common electromagnetic field C Anastopoulos, S Shresta, BL Hu Quantum Information Processing 8 (6), 549-563 , 2009 2009 Citations: 45
Frequently asked questions about decoherence C Anastopoulos International Journal of Theoretical Physics 41 (8), 1573-1590 , 2002 2002 Citations: 45
Gravitational decoherence: A thematic overview C Anastopoulos, BL Hu AVS Quantum Science 4 (1) , 2022 2022 Citations: 41
