| Records |
| Author |
Alicki, R.; Barenboim, G.; Jenkins, A. |
Title  |
Quantum thermodynamics of de Sitter space |
Type |
Journal Article |
| Year |
2023 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
| Volume |
108 |
Issue |
12 |
Pages |
123530 - 13pp |
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| Abstract |
We consider the local physics of an open quantum system embedded in an expanding three-dimensional space x, evolving in cosmological time t, weakly coupled to a massless quantum field. We derive the corresponding Markovian master equation for the system's nonunitary evolution and show that, for a de Sitter space with Hubble parameter h 1/4 const, the background fields act as a physical heat bath with temperature TdS 1/4 h/2z. The energy density of this bath obeys the Stefan-Boltzmann law pdS proportional to h4. We comment on how these results clarify the thermodynamics of de Sitter space and support previous arguments for its instability in the infrared. The cosmological implications are considered in an accompanying Letter. |
| Address |
[Alicki, Robert; Jenkins, Alejandro] Univ Gdansk, Int Ctr Theory Quantum Technol ICTQT, PL-80308 Gdansk, Poland, Email: robert.alicki@ug.edu.pl; |
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| Publisher |
Amer Physical Soc |
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| Language |
English |
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| ISSN |
2470-0010 |
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| Notes |
WOS:001145885800017 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
| Call Number |
IFIC @ pastor @ |
Serial |
5918 |
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| Author |
Araujo Filho, A.A.; Reis, J.A.A.S.; Ghosh, S. |
| Title |
Quantum gases on a torus |
Type |
Journal Article |
| Year |
2023 |
Publication |
International Journal of Geometric Methods in Modern Physics |
Abbreviated Journal |
Int. J. Geom. Methods Mod. Phys. |
| Volume |
20 |
Issue |
10 |
Pages |
2350178 - 19pp |
| Keywords |
Thermodynamic properties; non-Cartesian geometries; grand canonical ensemble; noninteracting and interacting quantum gases; spinless; bosons and fermion particles |
| Abstract |
This paper is aimed at studying the thermodynamic properties of quantum gases confined to a torus. To do that, we consider noninteracting gases within the grand canonical ensemble formalism. In this context, fermions and bosons are taken into account and the calculations are properly provided in both analytical and numerical manners. In particular, the system turns out to be sensitive to the topological parameter under consideration: the winding number. Furthermore, we also derive a model in order to take into account interacting quantum gases. To corroborate our results, we implement such a method for two different scenarios: a ring and a torus. |
| Address |
[Araujo Filho, A. A.] Univ Fed Ceara UFC, Dept Fis, Campus Pici,CP 6030, BR-60455760 Fortaleza, CE, Brazil, Email: dilto@fisica.ufc.br; |
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| Publisher |
World Scientific Publ Co Pte Ltd |
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English |
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0219-8878 |
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Conference |
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| Notes |
WOS:000988814200003 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
| Call Number |
IFIC @ pastor @ |
Serial |
5553 |
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| Author |
Balbinot, R.; Fabbri, A. |
| Title |
Quantum energy momentum tensor and equal time correlations in a Reissner-Nordström black hole |
Type |
Journal Article |
| Year |
2023 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
| Volume |
108 |
Issue |
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Pages |
045004 - 9pp |
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| Abstract |
We consider a Reissner-Nordström black hole formed by the collapse of a charged null shell. The renormalized expectation values of the energy-momentum tensor operator for a massless scalar field propagating in the two-dimensional section of this spacetime are given. We then analyze the across-the-horizon correlations of the related energy density operator for free-falling observers to reveal the correlations between the Hawking particles and their interior partners. |
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no |
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yes |
International Collaboration |
yes |
| Call Number |
IFIC @ pastor @ |
Serial |
6093 |
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| Author |
Beltran-Palau, P.; del Rio, A.; Navarro-Salas, J. |
| Title |
Quantum corrections to the Schwarzschild metric from vacuum polarization |
Type |
Journal Article |
| Year |
2023 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
| Volume |
107 |
Issue |
8 |
Pages |
085023 - 15pp |
| Keywords |
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| Abstract |
We explore static and spherically symmetric solutions of the 4-dimensional semiclassical Einstein's equations using the quantum vacuum polarization of a conformal field as a source. These solutions may be of interest for the study of exotic compact objects (ECOs). The full backreaction problem is addressed by solving the semiclassical Tolman-Oppenheimer-Volkoff (TOV) equations making use of effective equations of state inspired by the trace anomaly and an extra simplifying and reasonable assumption. We combine analytical and numerical techniques to solve the resulting differential equations, both perturbatively and nonperturbatively in h. In all cases the solution is similar to the Schwarzschild metric up p ffiffito the vicinity of the classical horizon r = 2M. However, at r = 2M + epsilon, with epsilon similar to O(root h), we find a coordinate singularity. In the case of matching with a static star, this leads to an upper bound in the compactness, and sets a constraint on the family of stable ECOs. We also study the corrections that the quantum-vacuum polarization induces on the propagation of waves, and discuss the implications. For the pure vacuum case, we can further extend the solution by using appropriate coordinates until we reach another singular point, where this time a null curvature singularity arises and prevents extending beyond. This picture qualitatively agrees with the results obtained in the effective two-dimensional approach, and reinforces the latter as a reasonable method. |
| Address |
[Beltran-Palau, Pau; Navarro-Salas, Jose] Univ Valencia, Dept Fis Teor, Burjassot 46100, Valencia, Spain, Email: pau.beltran@uv.es; |
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| Publisher |
Amer Physical Soc |
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English |
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2470-0010 |
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Conference |
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| Notes |
WOS:000988649200017 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
| Call Number |
IFIC @ pastor @ |
Serial |
5543 |
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| Author |
Nzongani, U.; Zylberman, J.; Doncecchi, C.E.; Perez, A.; Debbasch, F.; Arnault, P. |
| Title |
Quantum circuits for discrete-time quantum walks with position-dependent coin operator |
Type |
Journal Article |
| Year |
2023 |
Publication |
Quantum Information Processing |
Abbreviated Journal |
Quantum Inf. Process. |
| Volume |
22 |
Issue |
7 |
Pages |
270 - 46pp |
| Keywords |
Quantum walks; Quantum circuits; Quantum simulation |
| Abstract |
The aim of this paper is to build quantum circuits that implement discrete-time quantum walks having an arbitrary position-dependent coin operator. The position of the walker is encoded in base 2: with n wires, each corresponding to one qubit, we encode 2(n) position states. The data necessary to define an arbitrary position-dependent coin operator is therefore exponential in n. Hence, the exponentiality will necessarily appear somewhere in our circuits. We first propose a circuit implementing the position-dependent coin operator, that is naive, in the sense that it has exponential depth and implements sequentially all appropriate position-dependent coin operators. We then propose a circuit that “transfers” all the depth into ancillae, yielding a final depth that is linear in n at the cost of an exponential number of ancillae. Themain idea of this linear-depth circuit is to implement in parallel all coin operators at the different positions. Reducing the depth exponentially at the cost of having an exponential number of ancillae is a goal which has already been achieved for the problem of loading classical data on a quantum circuit (Araujo in Sci Rep 11:6329, 2021) (notice that such a circuit can be used to load the initial state of the walker). Here, we achieve this goal for the problem of applying a position-dependent coin operator in a discrete-time quantum walk. Finally, we extend the result of Welch (New J Phys 16:033040, 2014) from position-dependent unitaries which are diagonal in the position basis to position-dependent 2 x 2-block-diagonal unitaries: indeed, we show that for a position dependence of the coin operator (the block-diagonal unitary) which is smooth enough, one can find an efficient quantum-circuit implementation approximating the coin operator up to an error epsilon (in terms of the spectral norm), the depth and size of which scale as O(1/epsilon). A typical application of the efficient implementation would be the quantum simulation of a relativistic spin-1/2 particle on a lattice, coupled to a smooth external gauge field; notice that recently, quantum spatial-search schemes have been developed which use gauge fields as the oracle, to mark the vertex to be found (Zylberman in Entropy 23:1441, 2021), (Fredon arXiv:2210.13920). A typical application of the linear-depth circuit would be when there is spatial noise on the coin operator (and hence a non-smooth dependence in the position). |
| Address |
[Nzongani, Ugo; Doncecchi, Carlo-Elia; Arnault, Pablo] Univ Paris Saclay, CNRS, INRIA, Lab Methodes Formelles,ENS Paris Saclay, F-91190 Gif Sur Yvette, France, Email: ugo.nzongani@universite-paris-saclay.fr; |
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| Publisher |
Springer |
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English |
Summary Language |
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Series Issue |
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Edition |
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| ISSN |
1570-0755 |
ISBN |
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Expedition |
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Conference |
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| Notes |
WOS:001022408900002 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
| Call Number |
IFIC @ pastor @ |
Serial |
5587 |
| Permanent link to this record |
