arXiv subjects

Dipankar Barman

Publications and source records attributed to Dipankar Barman.

10 recordsLinked to original sources

arXiv2026

Detector's response to coherent Rindler and Minkowski photons

We observe that the transition probability in a static two-level quantum detector interacting with a coherent Rindler field mode differs from that of the Rindler detector interacting with a coherent Minkowski field mode. The situation does not change in the quantum detector's response in the semiclassical limit of the field state. This we investigate in $(1+1)$ and $(3+1)$-spacetime dimensions. Interestingly, in $(1+1)$-dimensions, the transition probabilities of the ``classical'' detector in the semiclassical limit of the field state for these two scenarios appear to be identical when the field mode and detector frequencies are taken to be the same. However, in $(3+1)$ dimensions, the detector transition probabilities calculated under the large-acceleration condition do not exhibit such a signature. The implications of these observations are also discussed.

quant-ph↗

arXiv2025

Can spacetime fluctuations generate entanglement between co-moving accelerated detectors?

Recent studies [Class. Quant. Grav. 42, 03LT01 (2025); Phys. Rev. D 111, 045023 (2025)] indicate that in a nested sequence of Rindler wedges, vacuum of former Rindler frame appears to be thermally populated for an observer in shifted Rindler frame. Interestingly, this thermality is independent of shift parameter as long as it is non-zero and therefore arises even if the shift parameter is as small as Planck length. Building on this insight, we propose a set-up involving two atoms accelerating with identical acceleration. We find that if their Rindler frames (consequently their trajectories) get infinitesimally separated, the atoms become entangled. Remarkably again, this entanglement, like the perceived thermality, is independent of the shift parameter, provided it is non-vanishing. Further we observe the vanishing of mutual information and discord. It implies the absence of both classical and non-classical correlations which are not related to entanglement. We investigate the dependence of entanglement on acceleration of the detectors. The present study indicates that the entanglement between two detectors, moving on the same Rindler wedge, is possible. Moreover, small spacetime fluctuations can lead to entanglement between detectors, moving along same classical trajectory. Hence we feel that such theoretical prediction has potential to probe the Planck length nature of spacetime.

gr-qc↗

arXiv2024

Mirror-enhanced acceleration-induced geometric phase

Fulling-Davies-Unruh effect contains great amount of theoretical importance in various branches of physics. Requirement of very high acceleration hinders its experimental evidence. We put forward an idea to experimentally probe this effect by utilizing the Pancharatnam-Berry phase of an accelerated atom in presence of mirrors. We show that for much lower accelerations, the phase gets significantly enhanced in the presence of mirrors. We propose a schematic design of an interferometric set-up to experimentally capture this effect by utilizing the phase difference between an accelerated and an inertial atoms. For the choice of hydrogen atoms and suitable separation between atoms and mirrors, the required acceleration can be very low.

quant-ph↗

arXiv2024

Field theory in Rindler frame and more on the correspondence with thermal field theory formalisms

Considering two accelerated observers with same acceleration in two timelike wedges of Rindler frame we calculate the Feynman-{\it like} propagators for a real scalar field in a thermal bath with respect to the Minkowski vacuum. Only the same wedge correlators are symmetric under the exchange of the {\it real} thermal bath and Unruh thermal bath, while the cross-wedge ones are not. Interestingly, they contain a cross term which is a collective effects of acceleration and thermal nature of field. Particularly the zero temperature description along with {\it no analytic continuation} between coordinates in right and left Rindler wedges, as expected, corresponds to usual thermofield-double formalism. However, unlike in later formulation, the two fields are now parts of the original system. Moreover it bears the features of a spacial case of closed-time formalism (CTP) where the Keldysh contour is along the increasing Rindler time in the respective Rindler wedges. Interestingly, we observe a new feature that the analytic continuation between the wedges provides the two more spacial cases of CTP. Hence Rindler-frame-field theory seems to be a viable candidate to deal thermal theory of fields and may illuminate the search for a bridge between the usual existing formalisms.

hep-th↗

arXiv2023

Are multiple reflecting boundaries capable of enhancing entanglement harvesting?

Quantum entanglement harvesting in the relativistic setup attracted a lot of attention in recent times. Acquiring more entanglement within two qubits may be very desirable to establish fruitful communication between them. On the other hand use of reflecting boundaries in a spacetime has close resemblance to the cavity quantum optomechanical systems. Here, in presence of two reflecting boundaries, we study the generation of entanglement between two uniformly accelerated Unruh-DeWitt detectors which are interacting with the background scalar fields. Like no boundary and single boundary situations, entanglement harvesting is possible for their motions in opposite Rindler wedges. We observe that the reflecting boundaries can play double roles. In some parameter space it causes suppression, while in other parameter space we can have enhancement of entanglement compared to no boundary and single boundary cases. Thus increase of boundaries has significant impact in this phenomena and a suitable choices of parameters provides desirable increment of it.

gr-qc↗

arXiv2023

Spontaneous entanglement leakage of two static entangled Unruh-DeWitt detectors

Two entangled two-level Unruh-DeWitt detectors, which are in rest, spontaneously loose entanglement when at least any one of them is not isolated from the environment quantum fields. For eternal interaction between the detectors and environment, the spontaneous emission from the detectors' exited states and vacuum fluctuations of field influence this negative effect. Consequently, it suggests that two entangled qubits become less communicated during their free-fall towards the black hole horizon.

quant-ph↗

arXiv2022

Entanglement harvesting from conformal vacuums between two Unruh-DeWitt detectors moving along null paths

It is well-known that the $(1+1)$ dimensional Schwarzschild and spatially flat FLRW spacetimes are conformally flat. This work examines entanglement harvesting from the conformal field vacuums in these spacetimes between two Unruh-DeWitt detectors, moving along outgoing null trajectories. In $(1+1)$ dimensional Schwarzschild spacetime, we considered the Boulware and Unruh vacuums for our investigations. In this analysis, one observes that while entanglement harvesting is possible in $(1+1)$ dimensional Schwarzschild and $(1+3)$ dimensional de Sitter spacetimes, it is not possible in the $(1+1)$ dimensional de Sitter background for the same set of parameters when the detectors move along the same outgoing null trajectory. The qualitative results from the Boulware and the Unruh vacuums are alike. Furthermore, we observed that the concurrence depends on the distance $d$ between the two null paths of the detectors periodically, and depending on the parameter values, there could be entanglement harvesting shadow points or regions. We also observe that the mutual information does not depend on $d$ in $(1+1)$ dimensional Schwarzschild and de Sitter spacetimes but periodically depends on it in $(1+3)$ dimensional de Sitter background. We also provide elucidation on the origin of the harvested entanglement.

gr-qc↗

arXiv2022

Entanglement harvesting between two inertial Unruh-DeWitt detectors from non-vacuum quantum fluctuations

Entanglement harvesting from the quantum field is a well-known fact that, in recent times, is being rigorously investigated further in flat and different curved backgrounds. The usually understood formulation studies the possibility of two uncorrelated Unruh-DeWitt detectors getting entangled over time due to the effects of quantum vacuum fluctuations. Our current work presents a thorough formulation to realize the entanglement harvesting from non-vacuum background fluctuations. In particular, we further consider single excitation field states and a pair of inertial detectors, respectively, in $(1+1)$ and $(1+3)$ dimensions for this investigation. Our main observation asserts that entanglement harvesting is suppressed compared to the vacuum fluctuations in this situation. Our other observations confirm a non-zero individual detector transition probability in this background and vanishing entanglement harvesting for parallel co-moving detectors. We look into the characteristics of the harvested entanglement and discuss its dependence on different system parameters.

gr-qc↗

arXiv2022

Constructing an entangled Unruh Otto engine and its efficiency

Uniformly accelerated frame mimics a thermal bath whose temperature is proportional to the proper acceleration. Using this phenomenon we give a detailed construction of an Otto cycle between two energy eigenstates of a system, consists of two entangled qubits. In the isochoric stages the thermal bath is being provided via the vacuum fluctuations of the background field for a monopole interaction by accelerating them. We find that making of Otto cycle is possible when one qubit is accelerating in the right Rindler wedge and other one is moving in the left Rindler wedge; i.e. in anti-parallel motion, with the initial composite state is a non-maximally entangled one. However, the efficiency greater than that of the usual single qubit quantum Otto engine is not possible. We provide values of the available parameters which make Otto cycle possible. On the other hand, Otto cycle is not possible if one considers the non-maximally entangled state for parallel motion. Moreover, for both initial symmetric and anti-symmetric Bell states we do not find any possibility of the cycle for qubits' parallel and anti-parallel motion.

quant-ph↗

arXiv2021

Role of thermal field in entanglement harvesting between two accelerated Unruh-DeWitt detectors

We investigate the effects of field temperature $T^{(f)}$ on the entanglement harvesting between two uniformly accelerated detectors. For their parallel motion, the thermal nature of fields does not produce any entanglement, and therefore, the outcome is the same as the non-thermal situation. On the contrary, $T^{(f)}$ affects entanglement harvesting when the detectors are in anti-parallel motion, i.e., when detectors $A$ and $B$ are in the right and left Rindler wedges, respectively. While for $T^{(f)}=0$ entanglement harvesting is possible for all values of $A$'s acceleration $a_A$, in the presence of temperature, it is possible only within a narrow range of $a_A$. In $(1+1)$ dimensions, the range starts from specific values and extends to infinity, and as we increase $T^{(f)}$, the minimum required value of $a_A$ for entanglement harvesting increases. Moreover, above a critical value $a_A=a_c$ harvesting increases as we increase $T^{(f)}$, which is just opposite to the accelerations below it. There are several critical values in $(1+3)$ dimensions when they are in different accelerations. Contrary to the single range in $(1+1)$ dimensions, here harvesting is possible within several discrete ranges of $a_A$. Interestingly, for equal accelerations, one has a single critical point, with nature quite similar to $(1+1)$ dimensional results. We also discuss the dependence of mutual information among these detectors on $a_A$ and $T^{(f)}$.

gr-qc↗