arXiv subjects

Niraj Kumar

Publications and source records attributed to Niraj Kumar.

At least 55 records · Page 3Linked to original sources

arXiv2021

Experimental demonstration of quantum advantage for NP verification with limited information

In recent years, many computational tasks have been proposed as candidates for showing a quantum computational advantage, that is an advantage in the time needed to perform the task using a quantum instead of a classical machine. Nevertheless, practical demonstrations of such an advantage remain particularly challenging because of the difficulty in bringing together all necessary theoretical and experimental ingredients. Here, we show an experimental demonstration of a quantum computational advantage in a prover-verifier interactive setting, where the computational task consists in the verification of an NP-complete problem by a verifier who only gets limited information about the proof sent by an untrusted prover in the form of a series of unentangled quantum states. We provide a simple linear optical implementation that can perform this verification task efficiently (within a few seconds), while we also provide strong evidence that, fixing the size of the proof, a classical computer would take much longer time (assuming only that it takes exponential time to solve an NP-complete problem). While our computational advantage concerns a specific task in a scenario of mostly theoretical interest, it brings us a step closer to potential useful applications, such as server-client quantum computing.

quant-ph↗

arXiv2021

Efficient Construction of Quantum Physical Unclonable Functions with Unitary t-designs

Quantum physical unclonable functions, or QPUFs, are rapidly emerging as theoretical hardware solutions to provide secure cryptographic functionalities such as key-exchange, message authentication, entity identification among others. Recent works have shown that in order to provide provable security of these solutions against any quantum polynomial time adversary, QPUFs are required to be a unitary sampled uniformly randomly from the Haar measure. This however is known to require an exponential amount of resources. In this work, we propose an efficient construction of these devices using unitary t-designs, called QPUF_t. Along the way, we modify the existing security definitions of QPUFs to include efficient constructions and showcase that QPUF_t still retains the provable security guarantees against a bounded quantum polynomial adversary with t-query access to the device. This also provides the first use case of unitary t-design construction for arbitrary t, as opposed to previous applications of t-designs where usually a few (relatively low) values of t are known to be useful for performing some task. We study the noise-resilience of QPUF_t against specific types of noise, unitary noise, and show that some resilience can be achieved particularly when the error rates affecting individual qubits become smaller as the system size increases. To make the noise-resilience more realistic and meaningful, we conclude that some notion of error mitigation or correction should be introduced.

quant-ph↗

arXiv2020

Variational Quantum Cloning: Improving Practicality for Quantum Cryptanalysis

Cryptanalysis on standard quantum cryptographic systems generally involves finding optimal adversarial attack strategies on the underlying protocols. The core principle of modelling quantum attacks in many cases reduces to the adversary's ability to clone unknown quantum states which facilitates the extraction of some meaningful secret information. Explicit optimal attack strategies typically require high computational resources due to large circuit depths or, in many cases, are unknown. In this work, we propose variational quantum cloning (VQC), a quantum machine learning based cryptanalysis algorithm which allows an adversary to obtain optimal (approximate) cloning strategies with short depth quantum circuits, trained using hybrid classical-quantum techniques. The algorithm contains operationally meaningful cost functions with theoretical guarantees, quantum circuit structure learning and gradient descent based optimisation. Our approach enables the end-to-end discovery of hardware efficient quantum circuits to clone specific families of quantum states, which in turn leads to an improvement in cloning fidelites when implemented on quantum hardware: the Rigetti Aspen chip. Finally, we connect these results to quantum cryptographic primitives, in particular quantum coin flipping. We derive attacks on two protocols as examples, based on quantum cloning and facilitated by VQC. As a result, our algorithm can improve near term attacks on these protocols, using approximate quantum cloning as a resource.

quant-ph↗

arXiv2020

Optimal quantum-programmable projective measurements with coherent states

We consider a device which can be programmed using coherent states of light to approximate a given projective measurement on an input coherent state. We provide and discuss three practical implementations of this programmable projective measurement device with linear optics, involving only balanced beam splitters and single photon threshold detectors. The three schemes optimally approximate any projective measurement onto a program coherent state in a non-destructive fashion. We further extend these to the case where there are no assumptions on the input state. In this setting, we show that our scheme enables an efficient verification of an unbounded untrusted source with only local coherent states, balanced beam splitters, and threshold detectors. Exploiting the link between programmable measurements and generalised swap test, we show as a direct application that our schemes provide an asymptotically quadratic improvement in existing quantum fingerprinting protocol to approximate the Euclidean distance between two unit vectors.

quant-ph↗

arXiv2020

Quantum versus Classical Generative Modelling in Finance

Finding a concrete use case for quantum computers in the near term is still an open question, with machine learning typically touted as one of the first fields which will be impacted by quantum technologies. In this work, we investigate and compare the capabilities of quantum versus classical models for the task of generative modelling in machine learning. We use a real world financial dataset consisting of correlated currency pairs and compare two models in their ability to learn the resulting distribution - a restricted Boltzmann machine, and a quantum circuit Born machine. We provide extensive numerical results indicating that the simulated Born machine always at least matches the performance of the Boltzmann machine in this task, and demonstrates superior performance as the model scales. We perform experiments on both simulated and physical quantum chips using the Rigetti forest platform, and also are able to partially train the largest instance to date of a quantum circuit Born machine on quantum hardware. Finally, by studying the entanglement capacity of the training Born machines, we find that entanglement typically plays a role in the problem instances which demonstrate an advantage over the Boltzmann machine.

quant-ph↗

arXiv2020

A Unified System for Aggression Identification in English Code-Mixed and Uni-Lingual Texts

Wide usage of social media platforms has increased the risk of aggression, which results in mental stress and affects the lives of people negatively like psychological agony, fighting behavior, and disrespect to others. Majority of such conversations contains code-mixed languages[28]. Additionally, the way used to express thought or communication style also changes from one social media plat-form to another platform (e.g., communication styles are different in twitter and Facebook). These all have increased the complexity of the problem. To solve these problems, we have introduced a unified and robust multi-modal deep learning architecture which works for English code-mixed dataset and uni-lingual English dataset both.The devised system, uses psycho-linguistic features and very ba-sic linguistic features. Our multi-modal deep learning architecture contains, Deep Pyramid CNN, Pooled BiLSTM, and Disconnected RNN(with Glove and FastText embedding, both). Finally, the system takes the decision based on model averaging. We evaluated our system on English Code-Mixed TRAC 2018 dataset and uni-lingual English dataset obtained from Kaggle. Experimental results show that our proposed system outperforms all the previous approaches on English code-mixed dataset and uni-lingual English dataset.

cs.CL↗

arXiv2019

Practically feasible robust quantum money with classical verification

We introduce a private quantum money scheme with the note verification procedure based on Sampling Matching, a problem in the one-way communication complexity model introduced by Kumar et al.[Nature Communications 10, Article number: 4152]. Our scheme involves a Bank that produces and distributes quantum notes, noteholders who are untrusted and trusted local verifiers of the Bank to whom the holders send their notes in order to carry out transactions. The key aspects of our money scheme include: note verification procedure requiring a single round classical interaction between the local verifier and Bank; fixed verification circuit that uses only passive linear optical components; re-usability of each note in our scheme which grows linearly with the size of note, and an unconditional security against any adversary trying to forge the banknote while tolerating the noise of up to 21.4%. We further describe a practical implementation technique of our money scheme using weak coherent states of light and the verification circuit involving a single 50/50beam splitter and 2 single-photon threshold detectors. Previous best-known matching based money scheme proposal [AA17] involves a verification circuit where the number of optical components increase proportionally to the increase in desired noise tolerance (robustness). In contrast, we achieve any desired noise tolerance (up to a maximal threshold value) with only a fixed number of optical components. This considerable reduction of components in our scheme enables us to reach the robustness values that are not feasible for any existing money scheme with the current technology.

quant-ph↗

arXiv2019

Stochastic modeling of phenotypic switching and chemoresistance in cancer cell populations

Phenotypic heterogeneity in cancer cells is widely observed and is often linked to drug resistance. In several cases, such heterogeneity in drug sensitivity of tumors is driven by stochastic and reversible acquisition of a drug tolerant phenotype by individual cells even in an isogenic population. Accumulating evidence further suggests that cell-fate transitions such as the epithelial to mesenchymal transition (EMT) are associated with drug resistance. In this study, we analyze stochastic models of phenotypic switching to provide a framework for analyzing cell-fate transitions such as EMT as a source of phenotypic variability in drug sensitivity. Motivated by our cell-culture based experimental observations connecting phenotypic switching in EMT and drug resistance, we analyze a coarse-grained model of phenotypic switching between two states in the presence of cytotoxic stress from chemotherapy. We derive analytical results for time-dependent probability distributions that provide insights into the rates of phenotypic switching and characterize initial phenotypic heterogeneity of cancer cells. The results obtained can also shed light on fundamental questions relating to adaptation and selection scenarios in tumor response to cytotoxic therapy.

q-bio.MN↗

arXiv2018

Experimental demonstration of quantum advantage for one-way communication complexity

The goal of demonstrating a quantum advantage with currently available experimental systems is of utmost importance in quantum information science. While this remains elusive for quantum computation, the field of communication complexity offers the possibility to already explore and showcase this advantage for useful tasks. Here, we define such a task, the Sampling Matching problem, which is inspired by the Hidden Matching problem and features an exponential gap between quantum and classical protocols in the one-way communication model. Our problem allows by its conception a photonic implementation based on encoding in the phase of coherent states of light, the use of a fixed size linear optic circuit, and single-photon detection. This enables us to demonstrate experimentally an advantage in the transmitted information resource beyond a threshold input size, which would have been impossible to reach for the original Hidden Matching problem. Our demonstration has implications in various communication and cryptographic settings, for example for quantum retrieval games and quantum money.

quant-ph↗

arXiv2018

Facile size-controllable synthesis of single crystalline \b{eta}-MnO2 nanorods under varying acidic strengths

A simple one-pot hydrothermal synthesis of single crystalline beta-MnO2 nanorods with diameters in the range of 10-40nm is reported. During the synthesis process, the acid molarities were varied from 1.1M down to 0.2M in steps of 0.3M while keeping the other reaction parameters constant, resulting in gradual transformation of the size of beta-MnO2 from micro to the nanoscale dimension. The as-synthesized nanorods exhibit soft ferromagnetic behavior and possess a high catalytic activity with an onset potential of -0.17V in facilitating the oxygen reduction reaction (ORR).

cond-mat.mes-hall↗

arXiv2018

Enhanced pseudocapacitance from finely ordered pristine alpha-MnO2 nanorods at favourably high current density using redox additive

A flexible technique is developed using hydrochloric acid to modify the redox reaction between potassium permanganate and sodium nitrite in order to grow ultrafine alpha-MnO2 nanorods, hydrothermally. The nanorods grown were 10-40 nm diameters in range. Not any crack, fissure, imperfection or dislocation is observed in the nanorods suggesting it to be finely ordered. Structure, phase and purity of as developed nanorods were determined using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Energy-dispersive X-ray spectroscopy. Peseudocapacitance of alpha-MnO2 nanorods was tested using a three electrode system. Considerably very high pseudocapacitance value of 643.5 F/g at 15 A/g current density was calculated from the galvanostatic discharge current measurement. Also excellent cyclability is observed with high retention of 90.5% after 4000 cycles. Highly uniform and confined morphology of the nanorods helps smooth the electron dynamics between electrode/electrolyte interfaces resulting in superior performance. Most importantly, the use of potassium ferricyanide as redox additive to KOH electrolyte was proved to be quite effective as it provides extra redox couple [Fe(CN)6]3n/[Fe(CN)6]4n which helps in further smoothening of electron transition thereby resulting in considerably superior pseudocapacitive performance.

cond-mat.mtrl-sci↗

arXiv2018

Morphological analysis of ultra fine α-MnO2 nanowires under different reaction conditions

A simple hydrothermal method was developed for the synthesis of ultra fine single-crystal α-MnO2 nanowires by only using potassium permanganate and sodium nitrite in acidic solution, without any seed or template. Detailed analysis of the obtained nanowires was done using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and high resolution transmission electron microscopy (HRTEM) measurements. The as-prepared α-MnO2 nanowires have the average diameter of 10-40nm and a length up to 0.1 to 2μm. Moreover, the effects of reaction temperature, time and reactant molar ratios on the morphology of the final product were studied in detail using field emission scanning electron microscopy (FESEM) measurements.

physics.app-ph↗

arXiv2018

Facile synthesis of 2D graphene oxide sheet enveloping ultrafine 1D LiMn2O4 as interconnected framework to enhance cathodic property for Li-ion battery

Cubic spinel lithium manganese oxide (LiMn2O4) has been able to attract a great deal of attention over the years as a promising cathode material for large scale lithium ion batteries. Here a facile hydrothermal route followed by solid state reaction is developed using as grown ultrafine alpha-MnO2 nanorods to prepare one dimensional LiMn2O4 with 10-50nm diameters. To enhance the cathodic property of these nanorods, a unique synthesis technique of heat treatment is developed to grow 2D graphene oxide sheet enveloping 1D LiMn2O4 as interconnected framework. This nanocomposite 3D porous cathode exhibits a high specific charge capacity of 130mAh/g at 0.05C rate and Coulombic efficiency of about 98% after 100 cycles in the potential window of 3.5 to 4.3V versus Li/Li+ with promising initial charge capacity retention of about 87%, and outstanding structural stability even after 100 cycles. Enhancement in the lithiation and delithiation processes leading to improved performance is likely to have its origin in the 2D conducting graphene oxide sheets. It allows for decreasing the Mn dissolution, improve the electron conductivity and reduce the Li-ion path diffusion inside the favourable morphology and crystallinity of the ultrafine 1D LiMn2O4 nanorods, giving rise to a promising cathode nanocomposite.

cond-mat.mtrl-sci↗

arXiv2018

Precise control on morphology of ultrafine LiMn2O4 nanorods as supercapacitor electrode via two-step hydrothermal method

We report three different synthesis routes while maintaining similar reaction conditions to choose an effective way to precisely control the growth of ultrafine one dimensional LiMn2O4 in the form of nanorods. We developed a novel method of mixing the precursors through hydrothermal, yielding low dimensional precursors for effective solid state reaction to synthesize the nanorods. However, to achieve these, highly uniform beta-MnO2 nanorods were initially grown as one of the main precursors. The uniformity observed in as grown beta-MnO2 nanorods using hydrothermal technique help to attract minute LiOH particles upon mixing over its highly confined nanoregime surface. This facilitated the solid state reaction between MnO2 and LiOH to develop one of the finest LiMn2O4 nanorods with diameters of 10 - 80 nm possessing high surface area of 88.294 m2/g. We find superior charge storage behaviour for these finely ordered 1D nanostructures as supercapacitor electrodes in KOH with K3Fe(CN)6 as electrolyte in contrast to Li2SO4. A high pseudo - capacitance of 653.5 F/g at 15 A/g is observed using galvanostatic discharge time with high retention capacity of 93% after 4000 cycles. The enhanced charge storage property may arise from the redox couple [Fe(CN)6]3n/[Fe(CN)6]4n and K+ ions of the electrolyte. To the best of our knowledge, we demonstrate for the first time the effectiveness of a two step hydrothermal method in tuning the supercapacitive behaviour of 1D LiMn2O4 in redox additive electrolyte.

physics.app-ph↗

arXiv2016

Efficient quantum communications with multiplexed coherent state fingerprints

We provide the first example of a communication model and a distributed task, for which there exists a realistic quantum protocol which is asymptotically more efficient than any classical protocol, both in the communication and the information resources. For this, we extend a recently proposed coherent state mapping for quantum communication protocols, introduce the notion of multiplexed coherent state fingerprints and show how to use them to design an efficient quantum protocol for estimating the Euclidean distance of two real vectors within a constant factor.

quant-ph↗

arXiv2016

OntoCat: Automatically categorizing knowledge in API Documentation

Most application development happens in the context of complex APIs; reference documentation for APIs has grown tremendously in variety, complexity, and volume, and can be difficult to navigate. There is a growing need to develop well-organized ways to access the knowledge latent in the documentation; several research efforts deal with the organization (ontology) of API-related knowledge. Extensive knowledge-engineering work, supported by a rigorous qualitative analysis, by Maalej & Robillard [3] has identified a useful taxonomy of API knowledge. Based on this taxonomy, we introduce a domain independent technique to extract the knowledge types from the given API reference documentation. Our system, OntoCat, introduces total nine different features and their semantic and statistical combinations to classify the different knowledge types. We tested OntoCat on python API reference documentation. Our experimental results show the effectiveness of the system and opens the scope of probably related research areas (i.e., user behavior, documentation quality, etc.).

cs.SE↗

arXiv2015

Nonlocality and conflicting interest games

Nonlocality enables two parties to win specific games with probabilities strictly higher than allowed by any classical theory. Nevertheless, all known such examples consider games where the two parties have a common interest, since they jointly win or lose the game. The main question we ask here is whether the nonlocal feature of quantum mechanics can offer an advantage in a scenario where the two parties have conflicting interests. We answer this in the affirmative by presenting a simple conflicting interest game, where quantum strategies outperform classical ones. Moreover, we show that our game has a fair quantum equilibrium with higher payoffs for both players than in any fair classical equilibrium. Finally, we play the game using a commercial entangled photon source and demonstrate experimentally the quantum advantage.

quant-ph↗

arXiv2014

Transcriptional bursting in gene expression: analytical results for general stochastic models

Gene expression in individual cells is highly variable and sporadic, often resulting in the synthesis of mRNAs and proteins in bursts. Bursting in gene expression is known to impact cell-fate in diverse systems ranging from latency in HIV-1 viral infections to cellular differentiation. It is generally assumed that bursts are geometrically distributed and that they arrive according to a Poisson process. On the other hand, recent single-cell experiments provide evidence for complex burst arrival processes, highlighting the need for more general stochastic models. To address this issue, we invoke a mapping between general models of gene expression and systems studied in queueing theory to derive exact analytical expressions for the moments associated with mRNA/protein steady-state distributions. These moments are then used to derive explicit conditions, based entirely on experimentally measurable quantities, that determine if the burst distributions deviate from the geometric distribution or if burst arrival deviates from a Poisson process. For non-Poisson arrivals, we develop approaches for accurate estimation of burst parameters.

q-bio.MN↗