arXiv subjects

Marcos L. W. Basso

Publications and source records attributed to Marcos L. W. Basso.

At least 19 recordsLinked to original sources

arXiv2026

On the quasiblack-hole limit of rotating charged fluids

We investigate the extremal quasiblack-hole (QBH) limit of stationary, axisymmetric charged perfect fluids in rigid or differential rotation, with and without pressure. We emphasize Weyl-type configurations, whose redshift factor is functionally related to the generalized electromagnetic potential. In this limit, the redshift factor vanishes throughout the fluid interior and the boundary becomes a quasihorizon. We require regular matter and electromagnetic fields and smooth matching to the exterior. Under suitable convergence assumptions, electromagnetic regularity and the approach to uniform rotation imply a constant generalized electromagnetic potential throughout the connected fluid interior, independently of the Weyl ansatz. With additional integrability conditions, the mass formula reduces to the extremal Kerr-Newman Smarr relation. For rigid rotation, we examine charged dust obeying a linear Weyl relation and fluids with pressure obeying the Kloster-Das or Guilfoyle relations. The linear Kloster-Das subclass becomes pressureless in the limit, whereas the general Guilfoyle case allows nonzero pressure. The Islam ansatz obstructs a regular limit when its coupling parameter, limiting potential, and limiting charge density are nonzero. For differential rotation, we analyze configurations with an identically vanishing Lorentz-force term and a linear Weyl subclass whose regularity requires control of angular-velocity gradients. Our results show that rotating Weyl-type systems admit extremal QBH limits much like their static counterparts, extending analyses of rotating dust distributions and identifying conditions for more general rotating charged fluids to be compatible with this limit.

gr-qc↗

arXiv2026

Heat distribution of quantum fields interacting with Unruh-DeWitt detectors

We introduce an operational framework for heat-exchange statistics between a quantum field and an Unruh-DeWitt detector in Minkowski spacetime. Using an interferometric protocol, we define the characteristic function of heat without projective measurements, consistently with relativistic causality. We derive perturbative expressions for this function and the heat distribution. In the vacuum, the statistics coincides with the low-intensity expansion of a unidirectional Poisson law, while for Kubo-Martin-Schwinger (KMS) states it has a bidirectional Poisson structure up to second order in perturbation theory. We study how fluctuation relations emerge from detector properties and field correlations, identifying regimes where they reduce to known heat-exchange fluctuation relations. We derive the entropic Landauer inequality as a specialization of the algebraic entropy-balance theorem of Jakšić and Pillet and verify it numerically within the perturbative detector-field interaction. We compare its tightness with a complementary Landauer bound derived from the full counting statistics of heat, analyzing their dependence on the detector's initial state and interaction time. We also formulate the first and second laws for the explicitly switched detector-field dynamics, identifying the external switching work that reconciles the field-energy gain with the detector-energy change. In the gapless and delta-switching regimes, where the dynamics admits a non-perturbative treatment, the characteristic function coincides with that of a bidirectional Poisson process, yielding an exact fluctuation theorem determined by the KMS condition. These results provide a consistent framework for heat statistics in relativistic quantum field theory and clarify the emergence of fluctuation relations.

gr-qc↗

arXiv2026

Bohr's complementarity

Quantum complementarity is a fundamental feature of quantum systems and has captivated the physics research community for nearly a century, with significant advancements emerging in recent decades. This review traces the historical evolution of the concept of complementarity, beginning with Bohr's original formulation. It then explores its modern quantification through complementarity relations and its profound connection to the foundational postulates of quantum theory. Furthermore, it delves into key related developments, such as the operational definition of complementarity in the context of incompatible observables, its potential links with quantum uncertainty relations and contextuality, its various applications, and other pertinent topics. This review aims to serve physicists interested in quantum resources, quantum correlations, and the foundational principles of quantum mechanics.

quant-ph↗

arXiv2025

A variational quantum algorithm for entanglement quantification

Quantum entanglement is a foundational resource in quantum information science, underpinning applications across physics. However, detecting and quantifying entanglement remains a significant challenge. In this article, we introduce a variational quantum algorithm inspired by Uhlmann's theorem to quantify the Bures entanglement of general quantum states, a method that naturally extends to other quantum resources, including genuine multipartite entanglement, quantum discord, quantum coherence, and total correlations, while also enabling reconstruction of the closest free states. The algorithm requires a polynomial number of ancillary qubits and circuit depth relative to the system size, dimensionality, and free state cardinality, making it scalable for practical implementations. Thus, it provides a versatile framework for quantifying quantum resources, demonstrated here through several applications.

quant-ph↗

arXiv2025

Entanglement swapping for partially entangled qudits and the role of quantum complementarity

We extend the entanglement swapping protocol (ESP) to partially entangled qudit states and analyze the process within the framework of complete complementarity relations (CCRs). Building on previous results for qubits, we show that the average distributed entanglement between two parties via ESP is bounded above by the initial entanglement of one of the input pairs, and also by the product of the initial entanglements. Notably, we find that using initial states with vanishing local quantum coherence is sufficient to capture the essential features of the protocol, simplifying the analysis. By exploring the cases of qubits and qutrits, we observe that the upper bound on the average distributed entanglement -- expressed in terms of the product of the initial entanglements -- can be improved, and we conjecture what this tighter bound might be. Finally, we discuss the role of quantum complementarity in the ESP and show how local predictability constrains the entanglement that can be operationally distributed via ESP.

quant-ph↗

arXiv2025

Work distribution of quantum fields in static curved spacetimes

We investigate the formulation of work distributions for quantum scalar fields in static curved spacetimes by extending the Ramsey interferometric protocol originally developed in previous works for flat spacetimes. The use of Unruh-DeWitt particle detectors provides a causally consistent framework to define and measure work statistics, avoiding the limitations of the two-time projective measurement scheme in relativistic quantum field theory. We derive a non-perturbative expression for the characteristic function of the quantum field and apply it to thermal Kubo-Martin-Schwinger (KMS) states, showing that the resulting work distributions satisfy both the Crooks fluctuation theorem and the Jarzynski equality. Furthermore, we analyse the case of a pointlike detector, obtaining compact expressions for the first two moments of the work distribution, allowing us to recover the standard fluctuation-dissipation relation in the high-temperature limit. Our results demonstrate that fluctuation theorems hold for quantum fields interacting with Unruh-DeWitt particle detectors in static curved spacetimes.

quant-ph↗

arXiv2025

Kerr-Newman outside a rotating de Sitter-type core: A rotating version of the Lemos-Zanchin electrically charged solution

A rotating version of the solution of the Einstein-Maxwell system of equations modeling static electrically charged regular black holes by Lemos and Zanchin [Phys. Rev. D 83, 124005 (2011)] is obtained in the present work. The full rotating geometry consists of the Kerr-Newman exterior geometry outside a rotating de Sitter-type core, with an electrically charged spheroidal shell at the boundary. The properties of the entire rotating solution, such as electromagnetic charge and current distributions, curvature regularity, energy-momentum tensor, and energy conditions, are thoroughly examined, revealing various types of charged rotating objects. We also study in detail the possible electromagnetic fields allowed in the interior region of the spheroidal shell of charge. By assuming that the interior geometry is described by the Gürses-Gürsey metric with an arbitrary mass function, we show that no well-behaved electromagnetic field is allowed in the interior region if it is devoid of electromagnetic sources. We also note that, although the overall electric charge of the static solution is preserved, the arbitrariness of the algorithm allows us to propose different electromagnetic fields and charge distributions for the same geometry of the interior region, together with different charge densities on the rotating boundary shell, without changing the exterior Kerr-Newman solution. For a particular choice of the interior electromagnetic fields, we show that it is possible to interpret the rotating de Sitter fluid as being electrically polarized due to the presence of the rotating charged spheroidal shell, despite the absence of net electric charge within the interior region, which is instead concentrated solely on the charged shell, with the interior medium behaving as a perfect conductor with infinite conductivity.

gr-qc↗

arXiv2025

Regular Kerr black holes: Junction conditions and the matter content across the ring

Regular rotating black holes are usually described by a metric of the Kerr-Schild form with a particular mass function that is chosen to avoid the ring singularity of the Kerr metric and which approaches the Kerr metric at the asymptotic limit. However, as is well known, even for a class of well-behaved mass functions, the curvature scalars present a discontinuity in the equatorial plane at the ring. This discontinuity has been associated with the presence of a string of matter that joins the interior and exterior regions along the equatorial plane. By using the Darmois-Israel junction conditions, we analyze all four possible combinations of the normal vector orientations on each side of the ring, construct the complete stress-energy momentum tensor of the string, and interpret each resulting solution. We show that, out of the four possibilities, only one of the four models for the string solution at the ring yields the appropriate asymptotic geometry. In such a case, the string bears a fluid with nonzero pressure, but with a vanishing line energy density, and it does not rotate at all. Finally, taking an appropriate metric for the exterior region, we also discuss a different scenario in which the matter source at the ring is a rotating lightlike fluid.

gr-qc↗

arXiv2025

Quantum fluctuation theorem in a curved spacetime

The interplay between thermodynamics, general relativity and quantum mechanics has long intrigued researchers. Recently, important advances have been obtained in thermodynamics, mainly regarding its application to the quantum domain through fluctuation theorems. In this letter, we apply Fermi normal coordinates to report a fully general relativistic detailed quantum fluctuation theorem based on the two point measurement scheme. We demonstrate how the spacetime curvature can produce entropy in a localized quantum system moving in a general spacetime. The example of a quantum harmonic oscillator living in an expanding universe is presented. This result implies that entropy production is strongly observer dependent and deeply connects the arrow of time with the causal structure of the spacetime.

gr-qc↗

arXiv2024

An Updated Quantum Complementarity Principle

Bohr's complementarity principle has long been a fundamental concept in quantum mechanics, positing that, within a given experimental setup, a quantum system (or quanton) can exhibit either its wave-like character, denoted as $W$, or its particle-like character, denoted as $P$, but not both simultaneously. Modern interpretations of Bohr's complementarity principle acknowledge the coexistence of these aspects in the same experiment while introducing the constraint $W + P \le α$. Notably, estimations of $W$ or $P$ frequently rely on indirect retrodiction methods, a practice that has led to the claim of the violation of Bohr's complementarity principle. By taking a different route, recent advancements demonstrate that quantum complementarity relations can be rigorously derived from the axioms of quantum mechanics. To reconcile these observations and eliminate potential paradoxes or violations, we propose an updated formulation for the quantum complementarity principle, which is stated as follows: \textit{For a given quantum state preparation $ρ_t$ at a specific instant of time $t$, the wave and particle behaviors of a quanton are constrained by a complementarity relation $\mathfrak{W}(ρ_t) + \mathfrak{P}(ρ_t) \le α(d)$, which is derived directly from the axioms of quantum mechanics.}

quant-ph↗

arXiv2024

Compact regular objects from an electrified Tolman-like density: A new interior region for the Kerr-Newman spacetime

Charged static and rotating objects as solutions of the Einstein-Maxwell field equations are obtained and studied in the present work. The full spacetime geometry is obtained by matching two spacetime regions, an interior region containing electrified matter and an exterior electrovacuum region. In the static case, the interior region contains a spherically symmetric distribution of matter constituted by a de Sitter-type perfect fluid with electric charge, whose energy density profile is given by a Tolman-like relation. The interior solution is smoothly matched with the exterior Reissner-Nordström electrovacuum solution, thus producing different kinds of objects, such as charged regular black holes and overcharged tension stars, that we analyze in detail. We also investigate the connection between the present static solution and the regular black holes with a de Sitter core presented in the work by Lemos and Zanchin [Phys. Rev. D 83, 124005 (2011)]. We then employ the Gürses-Gürsey metric and apply the Newman-Janis algorithm to construct a charged rotating interior geometry from the static interior solution. The resulting interior metric and the electromagnetic field are smoothly matched to the exterior Kerr-Newman electrovacuum solution, thus producing a regular interior for the exterior Kerr-Newman geometry. The main properties of the complete rotating solution are analyzed in detail, showing that different kinds of rotating objects, such as charged rotating black holes and other charged rotating objects, also emerge in this solution.

gr-qc↗

arXiv2024

Efficient fidelity estimation: Alternative derivation and related applications

In [Phys. Rev. A 107, 012427 (2023)], A. J. Baldwin and J. A. Jones proved that Uhlmann-Jozsa's fidelity between two quantum states $ρ$ and $σ$, i.e., $F(ρ,σ)~:=~(Tr\sqrt{\sqrtρσ\sqrtρ})^2$, can be written in a simplified form as $F(ρ,σ) = (Tr\sqrt{ρσ})^2$. In this article, we give an alternative proof of this result, using a function power series expansion and the properties of the trace function. Our approach not only reinforces the validity of the simplified expression but also facilitates the exploration of novel dissimilarity functions for quantum states and more complex trace functions of a density operator.

quant-ph↗

arXiv2024

Unveiling quantum complementarity tradeoffs in relativistic scenarios

Complementarity plays a pivotal role in understanding a diverse range of quantum phenomena. Here, we show how the tradeoff between quantities of a complete complementarity relation is modified in an arbitrary spacetime for a particle with an internal spin. This effect stems from local Wigner rotations in the spacetime, which couple the spin to the system's external degrees of freedom. To conduct our study, we utilize two generalized delayed-choice interferometers. Despite differences in complementarity tradeoffs inside the interferometers, the interferometric visibility of both setups coincides in any relativistic regime. Our results extend the finding that general relativity induces a universal decoherence effect on quantum superpositions, as local Wigner rotations, being purely kinematical, preclude any spin dynamics. To illustrate, we analyze the Newtonian limit of our results.

quant-ph↗

arXiv2023

Rotating charged fluids: Theorems and results for Weyl-type systems

We perform a systematic study of rotating charged fluids, and extend several well known theorems regarding static Weyl-type systems which were recently compiled by Lemos and Zanchin [Phys. Rev. D 80, 024010 (2009)] to rotating and axisymmetric systems. Static Weyl-type systems are composed by static charged fluid configurations obeying the Newton-Maxwell or the Einstein-Maxwell systems of equations in which the electric potential $ϕ$ and the timelike metric potential $g_{tt}\equiv - W^ 2$ satisfy the Weyl hypothesis, i.e., $W=W(ϕ)$. In the present analysis, both the Newton-Maxwell and Einstein-Maxwell theories that describe non-relativistic and relativistic systems, respectively, are used to perform a detailed analysis of the general properties of rotating charged fluids rotating charged dust as well as rotating charged fluids with pressure in four-dimensional spacetimes. In comparison to the static (nonrotating) systems, two additional potentials, a metric potential related to rotation and an electromagnetic potential related to the magnetic field, come into play for rotating systems. In each case, constraints between the fluid quantities and the metric and electromagnetic potentials are identified in order to generalize the theorems holding for static charged systems to rotating charged systems. New theorems regarding equilibrium configurations with differential rotation in both the Newtonian and the relativistic theories are stated and proved. For rigidly rotating charged fluids in the Einstein-Maxwell theory, a new ansatz involving the gradient of the metric potentials and the gradient of the electromagnetic potentials is considered in order to prove new theorems. Such an ansatz leads to new constraints between the fluid quantities and field potentials, so implying new equations of state for the charged fluids.

gr-qc↗

arXiv2023

The irreversibility of relativistic time-dilation

The fluctuation relations, which characterize irreversible processes in Nature, are among the most important results in non-equilibrium physics. In short, these relations say that it is exponentially unlikely for us to observe a time-reversed process and, thus, establish the thermodynamic arrow of time pointing from low to high entropy. On the other hand, fundamental physical theories are invariant under time-reversal symmetry. Although in Newtonian and quantum physics the emergence of irreversible processes, as well as fluctuation relations, is relatively well understood, many problems arise when relativity enters the game. In this work, by considering a specific class of spacetimes, we explore the question of how the time-dilation effect enters into the fluctuation relations. We conclude that a positive entropy production emerges as a consequence of both the special relativistic and the gravitational (enclosed in the equivalence principle) time-dilation effects.

quant-ph↗

arXiv2023

Simulating noisy quantum channels via quantum state preparation algorithms

In Refs. [Phys. Rev. A 96, 062303 (2017)] and [Sci. China Phys. Mech. Astron. 61, 70311 (2018)], the authors reported an algorithm to simulate, in a circuit-based quantum computer, a general quantum channel (QC). However, the application of their algorithm is limited because it entails the solution of intricate non-linear systems of equations in order to obtain the quantum circuit to be implemented for the simulation. Motivated by this issue, in this article we identify and discuss a simple way to implement the simulation of QCs on any $d$-level quantum system through quantum state preparation algorithms, that have received much attention in the quantum information science literature lately. We exemplify the versatility of our protocol applying it to most well known qubit QCs, to some qudit QCs, and to simulate the effect of Lorentz transformations on spin states. We also regard the application of our protocol for initial mixed states. Most of the given application examples are demonstrated using IBM's quantum computers.

quant-ph↗

arXiv2023

Simulation of positive operator-valued measures and quantum instruments via quantum state preparation algorithms

In Ref. [Phys. Rev. A 100, 062317 (2019)], the authors reported an algorithm to implement, in a circuit-based quantum computer, a general quantum measurement (GQM) of a two-level quantum system, a qubit. Even though their algorithm seems right, its application involves the solution of an intricate non-linear system of equations in order to obtain the angles determining the quantum circuit to be implemented for the simulation. In this article, we identify and discuss a simple way to circumvent this issue and implement GQMs on any $d$-level quantum system through quantum state preparation algorithms. Using some examples for one qubit, one qutrit and two qubits, we illustrate the easy of application of our protocol. Besides, we show how one can utilize our protocol for simulating quantum instruments, for which we also give an example. All our examples are demonstrated using IBM's quantum processors.

quant-ph↗

arXiv2023

Quantum coherence versus interferometric visibility in a biased Mach-Zehnder interferometer

The double-slit interferometer and the Mach-Zehnder interferometer (MZI) with balanced beam splitters are prototypical setups for investigating the quantum wave-particle duality. These setups induced a quantitative association of interferometric visibility (IVI) with the wave aspect of a single quantum system (WAQ). Recently, it was realized that quantum coherence (QC) can be better suited than IVI for quantifying the WAQ in complementarity relations. In this article, we investigate a MZI with biased beam splitters both in the input and the output, and we show that in some cases the IVI is not adequate to quantify the WAQ since it does not reflect the behavior of the quantum coherence, even for a bi-dimensional closed quantum system. Using IBM quantum computers, we experimentally verify our theoretical findings by doing a full quantum simulation of the optical MZI with biased beam splitters.

quant-ph↗