Publications

Order by: publication date number of citations

• Quantum information and the C-theorem in de Sitter

  Nicolás Abate, Gonzalo Torroba

  SciPost Phys. 18, 029 (2025) · published 22 January 2025 | Toggle abstract · pdf

  Information-theoretic methods have led to significant advances in nonperturbative quantum field theory in flat space. In this work, we show that these ideas can be generalized to field theories in a fixed de Sitter space. Focusing on 1+1-dimensional field theories, we derive a boosted strong subadditivity inequality in de Sitter, and show that it implies a C-theorem for renormalization group flows. Additionally, using the relative entropy, we establish a Lorentzian bound on the entanglement and thermal entropies for a field theory inside the static patch. Finally, we discuss possible connections with recent developments using unitarity methods.

  2 citations

• Cosmological infrared subtractions & infrared-safe computables

  Paolo Benincasa, Francisco Vazão

  SciPost Phys. 18, 176 (2025) · published 4 June 2025 | Toggle abstract · pdf

  Cosmological observables in perturbation theory turn out to be plagued with infrared divergences, which represents both a conceptual and computational challenge. In this paper we present a proof of concept for a systematic procedure to remove these divergences in a large class of scalar cosmological integrals and consistently define an infrared safe computable in perturbation theory. We provide diagrammatic rules which are based on the nestohedra underlying the asymptotic structure of such integrals.

  2 citations

• Entanglement in the full state vector of boson sampling

  Yulong Qiao, Joonsuk Huh, Frank Grossmann

  SciPost Phys. 15, 007 (2023) · published 12 July 2023 | Toggle abstract · pdf

  The full state vector of boson sampling is generated by passing $S$ single photons through beam splitters of $M$ modes. We express the initial Fock state in terms of 2$^{S-1}$ generalized coherent states, making possible the exact application of the unitary evolution. Due to the favorable polynomial scaling of numerical effort in $M$, we can investigate Rényi entanglement entropies for moderate particle and huge mode numbers. We find symmetric Page curves with a maximum entropy at equal partition, which is almost independent on Rényi index. Furthermore, the maximum entropy as a function of mode index saturates for $M\geq S^2$ in the collision-free subspace case. The asymptotic value of the entropy increases linearly with $S$. In addition, we show that the build-up of the entanglement leads to a cusp in the asymmetric entanglement curve. Maximum entanglement is reached well before the mode population is distributed over the whole system.

  2 citations

• Using coherent dipion photoproduction to image gold nuclei

  Spencer R. Klein

  SciPost Phys. Proc. 8, 128 (2022) · published 13 July 2022 | Toggle abstract · pdf

  Vector meson photoproduction offers the opportunity to image target nuclei. The two-dimensional Fourier transform $d\sigma_{\rm coherent}/dt$ of coherent vector meson photoproduction gives the two-dimensional distribution of interaction sites in the target. Since vector meson photoproduction occurs, at lowest order, via two-gluon exchange, this is sensitive to gluon shadowing. We present an analysis of $\pi^+\pi^-$ photoproduction using data from the STAR detector and a study of $d\sigma_{\rm coherent}/dt$, with an emphasis on probing the nuclear shape and its systematic uncertainties.

  2 citations

• Insulator phases of Bose-Fermi mixtures induced by intraspecies next-neighbor interactions

  Felipe Gómez-Lozada, Roberto Franco, Jereson Silva-Valencia

  SciPost Phys. Core 8, 007 (2025) · published 21 January 2025 | Toggle abstract · pdf

  We study a one-dimensional mixture of two-color fermions and scalar bosons at the hardcore limit, focusing on the effect that the intraspecies next-neighbor interactions have on the zero-temperature ground state of the system for different fillings of each carrier. Exploring the problem's parameters, we observed that the nearest-neighbor interaction could favor or harm the well-known mixed Mott and spin-selective Mott insulators. We also found the emergence of three unusual insulating states with charge density wave (CDW) structures in which the orders of the carriers are out of phase between each other. For instance, the immiscible CDW appears only at half-filling bosonic density, whereas the mixed CDW state is characterized by equal densities of bosons and fermions. Finally, the spin-selective CDW couples the bosons and only one kind of fermions. Appropriate order parameters were proposed for each phase to obtain the critical parameters for the corresponding superfluid-insulator transition. Our results can inspire or contribute to understanding experiments in cold-atom setups with long-range interactions or recent reports involving quasiparticles in semiconductor heterostructures.

  2 citations

• Adiabatic state distribution using anti-ferromagnetic spin systems

  Koen Groenland

  SciPost Phys. 6, 011 (2019) · published 23 January 2019 | Toggle abstract · pdf

  Transporting quantum information is an important prerequisite for quantum computers. We study how this can be done in Heisenberg-coupled spin networks using adiabatic control over the coupling strengths. We find that qudits can be transferred and entangled pairs can be created between distant sites of bipartite graphs with a certain balance between the maximum spin of both parts, extending previous results that were limited to linear chains. The transfer fidelity in a small star-shaped network is numerically analysed, and possible experimental implementations are discussed.

  2 citations

• Soliton confinement in the double sine-Gordon model

  Sergei Rutkevich

  SciPost Phys. 16, 042 (2024) · published 7 February 2024 | Toggle abstract · pdf

  The double sine-Gordon field theory in the weak confinement regime is studied. It represents the small non-integrable deformation of the standard sine-Gordon model caused by the cosine perturbation with the frequency reduced by the factor of 2. This perturbation leads to the confinement of the sine-Gordon solitons, which become coupled into the 'meson' bound states. We classify the meson states in the weak confinement regime, and obtain three asymptotic expansions for their masses, which can be used in different regions of the model parameters. It is shown, that the sine-Gordon breathers, slightly deformed by the perturbation term, transform into the mesons upon increase of the sine-Gordon coupling constant.

  2 citations

• Electroweak double-box integrals for Møller scattering

  Niklas Schwanemann, Stefan Weinzierl

  SciPost Phys. 18, 172 (2025) · published 3 June 2025 | Toggle abstract · pdf

  We present for Møller scattering planar and non-planar two-loop double-box integrals where three electroweak gauge bosons are exchanged between the fermion lines, among which at least one is a photon. These integrals are relevant for the NNLO electroweak corrections to Møller scattering.

  2 citations

• Constraints on physical computers in holographic spacetimes

  Aleksander M. Kubicki, Alex May, David Pérez-Garcia

  SciPost Phys. 16, 024 (2024) · published 23 January 2024 | Toggle abstract · pdf

  Within the setting of the AdS/CFT correspondence, we ask about the power of computers in the presence of gravity. We show that there are computations on $n$ qubits which cannot be implemented inside of black holes with entropy less than $O(2^n)$. To establish our claim, we argue computations happening inside the black hole must be implementable in a programmable quantum processor, so long as the inputs and description of the unitary to be run are not too large. We then prove a bound on quantum processors which shows many unitaries cannot be implemented inside the black hole, and further show some of these have short descriptions and act on small systems. These unitaries with short descriptions must be computationally forbidden from happening inside the black hole.

  2 citations

• A simple coin for a 2d entangled walk

  Ahmadullah Zahed, Kallol Sen

  SciPost Phys. Core 6, 048 (2023) · published 10 July 2023 | Toggle abstract · pdf

  We analyze the effect of a simple coin operator, built out of Bell pairs, in a 2d Discrete Quantum Random Walk (DQRW) problem. The specific form of the coin enables us to find analytical and closed form solutions to the recursion relations of the DQRW. The coin induces entanglement between the spin and position degrees of freedom, which oscillates with time and reaches a constant value asymptotically. We probe the entangling properties of the coin operator further, by two different measures. First, by integrating over the space of initial tensor product states, we determine the Entangling Power of the coin operator. Secondly, we compute the Generalized Relative Rényi Entropy between the corresponding density matrices for the entangled state and the initial pure unentangled state. Both the Entangling Power and Generalized Relative Rényi Entropy behaves similar to the entanglement with time. Finally, in the continuum limit, the specific coin operator reduces the 2d DQRW into two 1d massive fermions coupled to synthetic gauge fields, where both the mass term and the gauge fields are built out of the coin parameters.

  2 citations