arXiv subjects

Subhashish Banerjee

Publications and source records attributed to Subhashish Banerjee.

At least 73 records · Page 4Linked to original sources

arXiv2023

Impact of non-Markovian evolution on characterizations of quantum thermodynamics

Here we study the impact of non-Markovian evolution on prominent characteristics of quantum thermodynamics, such as ergotropy and power. These are benchmarked by the behavior of the quantum speed limit time. We make use of both geometric-based, particularly quantum Fisher and Wigner-Yanase information metric, and physical properties based-measures, particularly relative purity measure and relative entropy of coherence measure, to compute the quantum speed limit time. A simple non-Markovian model of a qubit in a bosonic bath exhibiting non-Markovian amplitude damping evolution is considered, which, from the quantum thermodynamic perspective with finite initial ergotropy, can be envisaged as a quantum battery. To this end, we explore the connections between the physical properties-based measures of quantum speed limit time and the coherent component of ergotropy. The non-Markovian evolution is shown to impact the recharging process of the quantum battery. Further, a connection between the discharging-charging cycle of the quantum battery and the geometric measures of quantum speed limit time is observed.

quant-ph↗

arXiv2023

Harnessing quantumness of states using discrete Wigner functions under (non)-Markovian quantum channels

The negativity of the discrete Wigner functions (DWFs) is a measure of non-classicality and is often used to quantify the degree of quantum coherence in a system. The study of Wigner negativity and its evolution under different quantum channels can provide insight into the stability and robustness of quantum states under their interaction with the environment, which is essential for developing practical quantum computing systems. We investigate the variation of DWF negativity of qubit, qutrit, and two-qubit systems under the action of (non)-Markovian random telegraph noise (RTN) and amplitude damping (AD) quantum channels. We construct different negative quantum states which can be used as a resource for quantum computation and quantum teleportation. The success of quantum computation and teleportation is estimated for these states under (non)-Markovian evolutions.

quant-ph↗

arXiv2023

A study of the quasi-probability distributions of the Tavis-Cummings model under different quantum channels

We study the dynamics of the spin and cavity field of the Tavis-Cummings model using quasi-probability distribution functions and second order coherence function, respectively. The effects of (non)-Markovian noise are considered. The relationship between the evolution of the cavity photon number, spin excitation, and atomic inversion under different quantum channels is observed. The equal-time second-order coherence function is used to study the sub-Poissonian behavior of light, and is compared with the two-time second-order coherence function in order to highlight the (anti)-bunching properties of the cavity radiation.

quant-ph↗

arXiv2023

Quantum correlations and speed limit of central spin system

In this article, we consider single, and two-qubit central spin systems interacting with spin baths and discuss their dynamical properties. We consider the cases of interacting and non-interacting spin baths and investigate the quantum speed limit (QSL) time of evolution. The impact of the size of the spin bath on the quantum speed limit for a single qubit central spin model is analyzed. We estimate the quantum correlations for (non-)interacting two central spin qubits and compare their dynamical behaviour with that of QSL time under various conditions. We show how QSL time could be availed to analyze the dynamics of quantum correlations.

quant-ph↗

arXiv2022

Quantum speed limit time: role of coherence

The minimum evolution time between multi-qubit quantum states is estimated for non-Markovian quantum channels. We consider the maximally coherent pure and mixed states as well as multi-qubit $X$ states as initial states and discuss the impact of initial coherence and the behaviour of coherence on their speed of evolution for both dephasing and dissipative processes. The role of the non-zero value of initial coherence under information backflow conditions for the non-unital dissipative process is revealed by the flow of quantum speed limit time ($τ_{QSL}$). The trade-off between mixedness and coherence on the speed limit time reveals the nature of the quantum process the states undergo. The complementarity effect between mixedness and coherence is more prominent in the quantum non-unital dissipation process. The parametric trajectory of speed limit time vividly depicts the difference in the evolution of pure and mixed initial states, and this could be used to distinguish between the unital and non-unital channels studied in this work. Our investigation of quantum speed limit time on multi-qubit entangled $X$ states reveals that $τ_{QSL}$ can be identified as a potential dynamical witness to distinguish multi-qubit states in the course of evolution.

quant-ph↗

arXiv2022

Characterization of Quantumness of non-Gaussian states under the influence of Gaussian channel

The impact of a noisy Gaussian channel on a wide range of non-Gaussian input states is studied in this work. The nonclassical nature of the states, both input and output, is developed by studying the corresponding photon statistics and quasi-probability distributions. It is found that photon addition has more robust quantum mechanical properties as compared to the photon subtraction case. The threshold value of the noise parameter corresponding to the transition from partial negative (W and P ) and zero (Q) to completely positive definite, at the center of phase space, depends not only on the average number of thermal photons in the state, but also on the squeezing parameter. In addition it is observed that the nonclassicality of the kth-number filtrated thermal state could be further enhanced by adding photon(s).

quant-ph↗

arXiv2022

Phase covariant channel: Quantum speed limit of evolution

The quantum speed of evolution for the phase covariant map is investigated. This involves absorption, emission and dephasing processes. We consider the maps under various combinations of the above processes to investigate the effect of phase covariant maps on quantum speed limit time. For absorption-free phase covariant maps, combinations of dissipative and CP-(in)divisible (non)-Markovian dephasing noises are considered. The role of coherence-mixedness balance on the speed limit time is checked in the presence of both vacuum and finite temperature effects. We also investigate the rate at which Holevo's information changes and the action quantum speed of evolution for specific cases of the phase covariant map.

quant-ph↗

arXiv2022

The effect of quantum memory on quantum speed limit time for CP-(in)divisible channels

Quantum speed limit time defines the limit on the minimum time required for a quantum system to evolve between two states. Investigation of bounds on speed limit time of quantum system under non-unitary evolution is of fundamental interest, as it reveals interesting connections to quantum (non-)Markovianity. Here, we discuss the characteristics of quantum speed limit time as a function of quantum memory, quantified as the deviation from temporal self-similarity of quantum dynamical maps for CP-divisible as well as indivisible maps, and show that the presence of quantum memory can speed up quantum evolution. This demonstrates the enhancement of the speed of quantum evolution in the presence of quantum memory for a wider class of channels than indicated by the CP-indivisibility criterion.

quant-ph↗

arXiv2022

Dynamics of two central spins immersed in spin baths

In this article we derive the exact dynamics of a two qubit (spin 1/2) system interacting centrally with separate fermionic baths composed of qubits in thermal state. Further, each spin of a bath is coupled to every other spin of the same bath. The corresponding dynamical map is constructed. It is used to analyse the non-Markovian nature of the two qubit central spin dynamics. We further observe the evolution of quantum correlations like entanglement and discord under the influence of the environmental interaction. Moreover, we demonstrate the comparison between this exact two qubit dynamics and the locally acting fermionic central spin model. This work is a stepping stone towards the realization of non-Markovian heat engines and other quantum thermal devices.

quant-ph↗

arXiv2022

Thermodynamics of one and two-qubit nonequilibrium heat engines running between squeezed thermal reservoirs

Quantum heat engines form an active field of research due to their potential applications. There are several phenomena that are unique to the quantum regime, some of which are known to give these engines an edge over their classical counterparts. In this work, we focus on the study of one and two-qubit finite-time Otto engines interacting with squeezed thermal baths, and discuss their important distinctions as well as the advantage of using the two-qubit engine. In particular, the two-qubit engine offers an interesting study of the interplay between the degree of squeezing and that of the coherence between the two qubits. We find that the two-qubit engine generally yields higher power than its one-qubit counterpart. The effective temperature of the squeezed baths can be calculated both for the one and two-qubit engines, and they tend to show an exponential growth with increase in squeezing parameters $r_h$ and $r_c$. It is also observed that by tuning the squeezing parameters, the machine can be made to work either in the engine or in the refrigerator mode. Additional effects due to the change in the inter-qubit separation have been studied.

cond-mat.stat-mech↗

arXiv2022

Non-uniform magnetic field as a booster for quantum speed limit: faster quantum information processing

We probe the quantum speed limit (QSL) of an electron when it is trapped in a non-uniform magnetic field. We show that the QSL increases to a large value, but within the regime of causality, by choosing a proper variation in magnetic fields. We also probe the dependence of QSL on spin of electron and find that it is higher for spin-down electron in the relativistic regime. This can be useful in achieving a faster speed of transmission of quantum information. Further, we use the Bremermann--Bekenstein bound to find a critical magnetic field that bridges the gap between non-relativistic and relativistic treatments and relates to the stability of matter. An analytical framework is developed. We also provide a plausible experimental design to supplement our theory.

quant-ph↗

arXiv2022

Indirect detection of Cosmological Constant from interacting open quantum system

We study the indirect detection of Cosmological Constant from an open quantum system of interacting spins, weakly interacting with a thermal bath, a massless scalar field minimally coupled with the static de Sitter background, by computing the spectroscopic shifts. By assuming pairwise interaction between spins, we construct states using a generalisation of the superposition principle. The corresponding spectroscopic shifts, caused by the effective Hamiltonian of the system due to Casimir Polder interaction, are seen to play a crucial role in predicting a very tiny value of the Cosmological Constant, in the static patch of de Sitter space, which is consistent with the observed value from the Planck measurements of the cosmic microwave background (CMB) anisotropies.

hep-th↗

arXiv2022

Quantum speed limit for the creation and decay of quantum correlations

We derive Margolus-Levitin and Mandelstamm-Tamm type bound on the quantum speed limit time for the creation and decay of quantum correlations by an amount in a quantum system evolving under the influence of its ambient environment. The minimum distance of a non-classical state from an appropriate set of classical states is a legitimate measure of the quantumness of the state. We consider entanglement and quantum discord measures of quantum correlations, quantified using the Bures distance-based measure. To demonstrate the impact of quantum noise on this speed limit time for quantum correlations, we estimate the quantum speed limit time for the creation and decay of quantum correlations for a two-qubit system under modified OUN dephasing and collective two-qubit decoherence channels.

quant-ph↗

arXiv2022

Estimation of von Neumann entropy of different light sources using array detectors

We employ a method involving an array detector to measure the transverse spatial variation of the von Neumann Entropy (VNE) associated with the polarization state of light for different light sources including the coherent light from a diode laser, the chaotic light from an LED, the fluorescent emission from a dye widely used as a contrast agent and also the downconverted output from the process of Spontaneous Parametric Down Conversion which has widespread applications in Quantum Optics as a source of entangled photon pairs. Additionally, we studied the variation of the Stokes parameters as well as von Neumann entropy with pixel binning in the array detector output.

physics.optics↗

arXiv2022

Hierarchy of quantum correlations under non-Markovian dynamics

We investigate the dynamics of quantum correlations (QC) under the effects of reservoir memory, as a resource for quantum information and computation tasks. Quantum correlations of two-qubit systems are used for implementing quantum teleportation successfully, and for investigating how teleportation fidelity, violation of Bell-CHSH inequality, quantum steering and entanglement are connected with each other under the influence of noisy environments. Both Markovian and non-Markovian channels are considered, and it is shown that the decay and revival of correlations follow the hierarchy of quantum correlations in the state space. Noise tolerance of quantum correlations are checked for different types of unital and non-unital quantum channels, with and without memory. The quantum speed limit time $(τ_{QSL})$ is investigated from the perspective of memory of quantum noise, and the corresponding dynamics is used to analyze the evolution of quantum correlations. We establish the connection between information backflow, quantum speed limit time and dynamics of quantum correlations for non-Markovian quantum channels.

quant-ph↗

arXiv2022

On the non-Markovianity of quantum semi-Markov processes

The non-Markovianity of the stochastic process called the quantum semi-Markov (QSM) process is studied using a recently proposed quantification of memory based on the deviation from semigroup evolution, that provides a unified description of divisible and indivisible channels. This is shown to bring out the property of QSM processes to exhibit memory effects even in the CP-divisible regime, in agreement with an earlier result. An operational meaning to the non-Markovian nature of semi-Markov processes is also provided.

quant-ph↗

arXiv2022

Thermal radiation in curved spacetime using influence functional formalism

Generalizing to relativistic exponential scaling and using the theory of noise from quantum fluctuations, it has been shown that one vacuum (Rindler, Hartle-Hawking, or Gibbons-Hawking for the cases of the uniformly accelerated detector, black hole, and de-Sitter universe, respectively) can be understood as resulting from the scaling of quantum noise in another vacuum. We explore this idea more generally to establish a flat spacetime and curved spacetime analogy. For this purpose, we start by examining noise kernels for free fields in some well-known curved spacetimes, e.g., the spacetime of a charged black hole, the spacetime of a Kerr black hole, Schwarzschild-de Sitter, Schwarzschild anti-de Sitter, and Reissner-Nordstrom de-Sitter spacetimes. Here, we consider a maximal analytical extension for all these spacetimes and different vacuum states. We show that the exponential scale transformation is responsible for the thermal nature of radiation.

gr-qc↗

arXiv2021

Local description of S-matrix in quantum field theory in curved spacetime using Riemann-normal coordinate

The success of the S-matrix in quantum field theory in Minkowski spacetime naturally demands the extension of the construction of the S-matrix in a general curved spacetime in a covariant manner. However, it is well-known that a global description of the S-matrix may not exist in an arbitrary curved spacetime. Here, we give a local construction of S-matrix in quantum field theory in curved spacetime using Riemann-normal coordinates which mimics the methods, generally used in Minkowski spacetime. Using this construction, the scattering amplitudes and cross-sections of some scattering processes are computed in a generic curved spacetime. Further, it is also shown that these observables can be used to probe features of curved spacetime as these local observables carry curvature-dependent corrections. Moreover, the compatibility of the local construction of the S-matrix with the spacetime symmetries is also discussed in detail.

hep-th↗