arXiv subjects

Prasanta K. Panigrahi

Publications and source records attributed to Prasanta K. Panigrahi.

At least 37 records · Page 2Linked to original sources

arXiv2025

Effect of polarisation on two-photon resonance in a large Zeeman manifold

In this study, we present numerical investigations on a large Zeeman manifold in an electromagnetically induced transparency (EIT) medium, focusing on the D1 and D2 lines of 87 Rb as our model system. We examine two distinct models comprising 13 and 16 energy levels, respectively, using pump-probe spectroscopy with varying polarization of the light fields. A longitudinal magnetic field is used, and the ellipticity of both light fields is varied with the constraint that both lights have orthogonal polarization. We discover that in the presence of a longitudinal magnetic field, the change in ellipticity of light polarization induces optical anisotropy. This anisotropy results from the uneven distribution of population among the ground Zeeman levels, leading to the absorption of weak probe light. For a large number of states interacting with different field components, the existence of a steady state depends upon the multi-photon resonance and phase matching conditions. A comment is made on why such conditions are not required in our model, and the assumptions and limitations of the model are also discussed. To validate our numerical findings, we perform experimental measurements at two different magnetic field strengths in the D2 line of 87 Rb. The experimental results align well with our numerical simulations. Specifically, we conclude that the probe transmission spectra at lower magnetic field values (up to 20 G) exhibit similarity for both the D1 and D2 lines of 87 Rb, effectively described by the 13-level model. However, at higher magnetic field values, a more complicated 16-level (or higher) system is necessary to accurately capture the response of the probe in D2 line.

physics.optics↗

arXiv2025

Coherent States in Classical Field Theory

We illustrate the emergence of classical analogue of coherent state and its generalisation in a purely classical field theoretical setting. Our algebraic approach makes use of the Poisson bracket and symmetries of the underlying field theory, in a complete parallel to the quantum construction. The classical phase space picture is found to play a key role in this construction.

hep-th↗

arXiv2025

Evolution of Entanglement Witness of Dicke State under Noise and Error Mitigation

The experimental verification of multipartite entangled states is essential for advancing quantum information processing. Entanglement witnesses (EWs) provide a widely used and experimentally accessible approach for detecting genuinely multipartite entangled states. In this work, we theoretically derive the entanglement witness for the four-qubit Dicke state and experimentally evaluate it on two distinct IBM 127-qubit Quantum Processing Units (QPUs), namely ibm\_sherbrook and ibm\_brisbane. A negative expectation value of the witness operator serves as a sufficient condition for confirming genuine multipartite entanglement. We report the maximum (negative) values of the witness achieved on these QPUs as $-0.178 \pm 0.009$ and $-0.169 \pm 0.002$, corresponding to two different state preparation protocols. Additionally, we theoretically investigate the effect of various noise channels on the genuine entanglement of a four-qubit Dicke state using the Qiskit Aer simulator. We show the behavior of the EW constructed under the assumption of Markovian and non-Markovian amplitude damping and depolarizing noises, bit-phase flip noise, and readout errors. We also investigate the effect of varying thermal relaxation time on the EW, depicting a bound on the $T_1$ time required for successful generation of a Dicke State on a superconducting QPU.

quant-ph↗

arXiv2025

Enhanced Rapid Detection of High-impedance Arc Faults in Medium Voltage Electrical Distribution Networks

High-impedance arc faults in AC power systems have the potential to lead to catastrophic accidents. However, significant challenges exist in identifying these faults because of the much weaker characteristics and variety when grounded with different surfaces. Previous research has concentrated predominantly on arc fault detection in low-voltage systems, leaving a significant gap in medium-voltage applications. In this work, a novel approach has been developed that enables rapid arc fault detection for medium-voltage distribution lines. In contrast to existing black-box feature-based approaches, the Hankel alternative view of the Koopman (HAVOK) analysis developed from nonlinear dynamics has been applied, which not only offers interpretable features but also opens up new application options in the area of arc fault detection. The method achieves a much faster detection speed in 0.45 ms, 99.36\% enhanced compared to harmonic randomness and waveform distortion method, thus making it suitable for real-time applications. It demonstrates the ability to detect arc faults across various scenarios, including different grounding surfaces and levels of system noise, boosting its practical importance for stakeholders in safety-critical industries.

eess.SY↗

arXiv2025

The Journey from Planck Distribution to Bose Statistics From Classical to Quantum Mechanics and Beyond

In 1924, Satyendra Nath Bose's pioneering work laid the foundation for Bose-Einstein statistics, which describes particles with integral spins. His derivation of Planck's law for blackbody radiation bypassed classical assumptions, relying instead on the statistical mechanics of light quanta. Bose's methodology addressed limitations in existing theories, such as Einstein's dependence on classical concepts like Wien's displacement law and Bohr's correspondence principle. Further, his work underscored the incompatibility between classical electrodynamics and quantum theory, proposing innovative statistical approaches to thermodynamic equilibrium. The insights from Bose's work extend beyond theoretical physics. As was immediately noticed by Einstein, for temperatures below a critical threshold, Bose-Einstein statistics predicts the formation of a Bose-Einstein condensate (BEC), where particles condense en-masse into the ground state. This quantum phenomenon on a macroscopic scale opened avenues to explore new technologies in recent times, apart from throwing light on new phases of matter. This article revisits Bose's groundbreaking contributions, highlighting their enduring impact on quantum mechanics, statistical physics, and field theory.

physics.hist-ph↗

arXiv2025

Experimental demonstration of the Bell-type inequalities for four qubit Dicke state using IBM Quantum Processing Units

Violation of the Bell-type inequalities is necessary to confirm the existence of nonlocality in nonclassical (entangled) states. We have designed a customized operator which is made of the sum of the Pauli matrices ($σ_x$, $σ_y$, and $σ_z$). We theoretically and experimentally investigate the violation of Bell-type inequalities using two- and four-qubit Dicke states on IBM Quantum Processing Units (QPUs). We compare two different state preparation methods for the four-qubit Dicke state -- gate-based and statevector-based -- and evaluate their performance on two IBM QPUs, \texttt{ibm\_kyiv} and \texttt{ibm\_sherbrook}. For the two-qubit case, we demonstrate clear violations of the CHSH inequality, with the highest observed Bell parameter reaching $2.821 \pm 0.0019$ using M3 error mitigation, which is within $0.7σ$ of the theoretical maximum $2\sqrt{2}$. In the four-qubit case, we employ a Bell-type inequality tailored for Dicke states and achieve a maximum violation of $2.607 \pm 0.029$ without the need for additional mitigation when using the statevector-based method. Our results reveal that advanced error mitigation techniques significantly enhance the observed violations in the gate-based method, while the statevector-based approach inherently yields more robust states with lower noise. This study highlights the critical role of state preparation and mitigation techniques in probing fundamental quantum correlations on near-term quantum hardware.

quant-ph↗

arXiv2025

Machine Learning assisted noise classification with Quantum Key Distribution protocols

We propose a hybrid protocol to classify quantum noises using supervised classical machine learning models and simple quantum key distribution protocols. We consider the quantum bit error rates (QBERs) generated in QKD schemes under consideration of different noises, and identify the noise channels with high accuracy for both training and test data. Our protocol classifies quantum noises with high accuracy under the assumption of two different scenarios; in one case we assume two remotely located parties share keys through noisy quantum channels, whereas, in the second case, we simulate the QKD protocols on a gate-based quantum computer, where the gates are afflicted with noise. Alongside efficient classification, our work also throws light on the difference in distribution characteristics of QBERs generated in these two scenarios. Finally, our method is based on classical post processing of data generated from very simplistic quantum protocols, making it readily implementable in the current era of noisy quantum computing with low number of qubits.

quant-ph↗

arXiv2025

Optimal sensing of photon addition and subtraction on nonclassical light

We demonstrate that the Wasserstein distance $W_{1}$ corresponding to optical tomograms of nonclassical states faithfully captures changes that arise due to photon addition to, or subtraction from, these states. $W_{1}$ is a true measure of distance in the quantum state space, and is sensitive to the underlying interference structures that arise in the tomogram after changes in the photon number. Our procedure is universally applicable to the cat and squeezed states, the former displaying the characteristic negativity in its Wigner function, while the latter does not do so. We explicate this in the case of the squeezed vacuum and even coherent states and show that photon addition (or subtraction) is mirrored in the shift in the intensity of specific regions in the tomogram. Further, we examine the dependence of $W_{1}$ on the squeezing parameter, and its sensitivity to different quadratures.

quant-ph↗

arXiv2025

A maximum concurrence criterion to investigate absolutely maximally entangled states

We propose a straightforward method to determine the maximal entanglement of pure states using the criterion of maximal I-concurrence, a measure of entanglement. The square of concurrence for a bipartition $X|X^\prime$ of a pure state is defined as $E^2_{X| X ^\prime}=2[1-tr({ρ_X}^2)]$. From this, we can infer that the concurrence $E_{X| X ^\prime}$ reaches its maximum when $tr({ρ_X}^2)$ is minimized. Using this approach, we identify numerous Absolutely Maximally Entangled (AME) pure states that exhibit maximal entanglement across all possible bipartitions. Conditions are derived for pure states to achieve maximal mixedness in all bipartitions, revealing that any pure state with an odd number of subsystem coefficients does not meet the AME criterion. Furthermore, we obtain equal maximal multipartite entangled pure states across all bipartitions using our maximal concurrence criterion.

quant-ph↗

arXiv2025

Lower bound of the expressibility of ansatzes for Variational Quantum Algorithms

The expressibility of an ansatz used in a variational quantum algorithm is defined as the uniformity with which it can explore the space of unitary matrices, i.e., its covering number. The expressibility of a particular ansatz has a well-defined upper bound [1]. In this work, we show that the expressibility also has a well-defined lower bound in the hypothesis space. We provide an analytical expression for the lower bound of the covering number, which is directly related to expressibility. Further, we provide numerical analysis to support our claim. By calculating the bond length of hydrogen molecule ($H_2$) using different ansatzes in a variational quantum eigensolver (VQE) setting, we study the variation of equilibrium energy error with circuit depths. We show that in each ansatz template, a plateau exists for a range of circuit depths, which we call the set of acceptable points, and the corresponding expressibility as the best expressive region. We report that the width of this best expressive region in the hypothesis space is inversely proportional to the average error. Our analysis reveals that alongside trainability, the lower bound of expressibility also plays a crucial role in selecting variational quantum ansatzes

quant-ph↗

arXiv2024

Quantum droplets and Schrödinger's cat states in atomic-molecular Bose-Einstein condensates

Explicit realization of quantum droplets, even and odd Schrödinger cat states is demonstrated in an atom-molecular Bose-Einstein condensate in the presence of interconversion and Kerr non-linear interactions. The crucial roles of both the $χ^2$-type nonlinearity and chemical potential in the formation of these macroscopic quantum states are shown, where the atomic condensate is in the cat state, with the corresponding molecular wave packet being a quantum droplet. The physical mechanism for their creation and common origin is established to be the non-linearity-induced self-trapping potentials, governed by photoassociation or Feshbach resonance, with the Kerr-type nonlinearities playing subdominant roles. The coexisting and controllable atom and molecular droplets are shown to realize the atom-molecular squeezed state with profiles ranging from Gaussian to flat-top super-Gaussian form. The Wigner functions are exhibited revealing the cat states' phase space interference and squeezing of droplets.

quant-ph↗

arXiv2024

Imprints of LGI violation in Mesons

Quantum mechanics has always proven emphatically as one of the main cornerstones in all of science since its inception. Initially, it has also faced many skeptics from many scientific proponents of its complete description of reality. However, John Bell once devised a theorem on quantitative grounds to show how local realism is expressed in quantum mechanics. As Bell's inequality claims the non-existence of local hidden variable theories, on the same footing, we have Leggett-Garg's Inequality (LGI), which sets a quantum-classical limit for temporally correlated quantum systems. In the context of particle physics, specially in the field of neutrino and meson oscillations, one can conveniently implement LGI to test the quantum foundations at the probability level. Here, we discuss the significant LGI violation characteristics in B- and K- meson oscillations, taking into account their decoherence, CP violation, and decay parameters. We have emphasized the fact that \textit{Tsirelson} bounds can be achieved under certain conditions. Our focal point is to show the signature of these bounds that appears only to specific alterations of decay and decoherence effects. Also, we discuss and comment on the behavior or effect of decoherence and decay widths playing out from the perspective of LGI by taking their available values from various experiments. This may help us to understand the underlying principles and techniques of neutral meson open quantum systems.

hep-ph↗

arXiv2024

Quantum Information Scrambling and Entanglement: An Elegant Mathematical Connection

Studying the behavior of quantum information scrambling in various quantum systems is an active area of research. Recently, Sharma et al. [K.K. Sharma, V.P Gerdt, Quantum Inf. Process 20, 195 (2021)] have shown the mathematical connection between quantum information scrambling (QIS) and bipartite entanglement in non-thermal states. In the present work, we elegantly generalize this mathematical connection and study such connections in X-states, non-maximally entangled Bell states, and Werner states

quant-ph↗

arXiv2024

NISQ-friendly measurement-based quantum clustering algorithms

Two novel measurement-based, quantum clustering algorithms are proposed based on quantum parallelism and entanglement. The first algorithm follows a divisive approach. The second algorithm is based on unsharp measurements, where we construct an effect operator with a Gaussian probability distribution to cluster similar data points. A major advantage of both algorithms is that they are simplistic in nature, easy to implement, and well suited for noisy intermediate scale quantum computers. We have successfully applied the first algorithm on a concentric circle data set, where the classical clustering approach fails, as well as on the Churrtiz data set of $130$ cities, where we show that the algorithm succeeds with very low quantum resources. We applied the second algorithm on the labeled Wisconsin breast cancer dataset, and found that it is able to classify the dataset with high accuracy using only $O(log(D))$ qubits and polynomial measurements, where $D$ is the maximal distance within any two points in the dataset. We also show that this algorithm works better with an assumed measurement error in the quantum system, making it extremely well-suited for NISQ devices.

quant-ph↗

arXiv2024

Fully Quantum Hash Function

We introduce a novel, \textit{fully} quantum hash (FQH) function within the quantum walk on a cycle framework. We incorporate deterministic quantum computation with a single qubit to replace classical post-processing, thus increasing the inherent security. Further, our proposed hash function exhibits zero collision rate and high reliability. We further show that it provides $ > 50\%$ avalanche on average, and is highly sensitive to the initial conditions. We show comparisons of several performance metrics for the proposed FQH with different settings as well as with existing protocols to prove its efficacy. FQH requires minimal quantum resources to produce a large hash value, providing security against the birthday attack. This innovative approach thus serves as an efficient hash function and lays the foundation for potential advancements in quantum cryptography by integrating the fully quantum hash generation protocol.

quant-ph↗

arXiv2024

Strain induced tunable band gap and optical properties of graphene on hexagonal boron nitride

In this study, we highlight the potential of strain engineering in graphene/hBN (hexagonal Boron nitride) 2D heterostructures, enabling their use as wide-range light absorbers with significant implications for optoelectronic applications. We systematically investigate the electronic and optical properties of graphene/hBN under the application of strain, considering various stacking geometries within the framework of density-functional theory. The semimetallic graphene layer upon aligning on the insulating hexagonal boron nitride sheet opens a few tens of meV band gap at the Dirac point due to the induced on-site energy differences on the two sublattices of graphene. Here, we demonstrate that by simultaneously tuning the interlayer distance and lattice constant, this band gap can be significantly increased to 1 eV. Interestingly, in both scenarios (small and large band gaps), the material undergoes a transition from a semiconductor to a semimetallic state. Importantly, the tunability of this band gap is strongly influenced by the specific stacking configuration. We further explored the optical properties across a broad spectrum, revealing that the presence of a strain-induced band gap fundamentally alters how light interacts with the system.

cond-mat.mes-hall↗

arXiv2024

Generation of intraparticle quantum correlations in amplitude damping channel and its robustness

Quantum correlations between two or more different degrees of freedom of the same particle is sometimes referred to as intraparticle entanglement. In this work, we study these intra-particle correlations between two different degrees of freedom under various decoherence channels viz. amplitude damping, depolarising and phase damping channels. We observe a unique feature of the amplitude damping channel, wherein entanglement is shown to arise starting from separable states. In case of non maximally entangled input states, in addition to entanglement sudden death, the creation of entanglement is also observed, having an asymptotic decay over a long time. These counter-intuitive behaviours arise due to the subtle interplay of channel and input state parameters, and are not seen for interparticle entanglement without consideration of non-Markovian noise. It is also not observed for maximally entangled input states. Furthermore, investigation of entanglement evolution in phase damping and depolarizing channels shows its robustness against decoherence as compared to interparticle entanglement.

quant-ph↗

arXiv2024

Neutral-atom qubits in atom-molecular BEC

Recently, neutral atoms have emerged as a promising platform for quantum computing, offering scalability. In this study, we showcase the realization of atomic qubits in atom-molecular Bose-Einstein condensate, belonging to three distinct classes. In the first case, the condensed molecules form a droplet platform with a flat-top configuration, facilitating effective isolation from both external environments and neighbouring molecules. The second atomic qubits have wavefunctions in the ``pulse" form, exhibiting power law behaviour, whereas the third one has ground and excited state wavefunctions in their respective composite forms, $\sech^2{βx}$ and $\sech{βx}\tanh{βx}$. The localization of the qubits depends on the chemical potential, which is governed by the photo association, providing effective control for qubit manipulation. The relevant parameters, such as energy level separation, healing length, and atom numbers, are found to be influenced by the non-linearity and strength of photo associations governing the behaviour of macroscopic qubits and molecular droplets.

quant-ph↗