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Aeysha Khalique

Publications and source records attributed to Aeysha Khalique.

14 recordsLinked to original sources

Scaling Network Topologies for Multi-User Entanglement Distribution

Future quantum internet relies on large-scale entanglement distribution. Quantum decoherence is a significant obstacle in large-scale networks, which otherwise perform better with multiple paths between the source and destination. We propose a new topology, connected tree, with a significant amount of redundant edges to support multi-path routing of entangled pairs. We qualitatively analyse the scalability of quantum networks to maximum user capacity in decoherence for different topologies. Our analysis shows that thin-connected tree networks can accommodate a larger number of user pairs than more evenly distributed lattice topology. We extend our analysis to quantum key distribution and show that the quantum network of a thin tree topology is more robust against decoherence and leads to better key distribution among multiple communicating parties.

quant-ph

IQNN-CS: Interpretable Quantum Neural Network for Credit Scoring

Credit scoring is a high-stakes task in financial services, where model decisions directly impact individuals' access to credit and are subject to strict regulatory scrutiny. While Quantum Machine Learning (QML) offers new computational capabilities, its black-box nature poses challenges for adoption in domains that demand transparency and trust. In this work, we present IQNN-CS, an interpretable quantum neural network framework designed for multiclass credit risk classification. The architecture combines a variational QNN with a suite of post-hoc explanation techniques tailored for structured data. To address the lack of structured interpretability in QML, we introduce Inter-Class Attribution Alignment (ICAA), a novel metric that quantifies attribution divergence across predicted classes, revealing how the model distinguishes between credit risk categories. Evaluated on two real-world credit datasets, IQNN-CS demonstrates stable training dynamics, competitive predictive performance, and enhanced interpretability. Our results highlight a practical path toward transparent and accountable QML models for financial decision-making.

cs.LG

Enabling CV-MDI-QKD for low squeezed states using non-Gaussian operations

We show the utility of photon added-then-subtracted (PAS) state and two photon replaced (2PR) state when used in continuous variables measurement device independent quantum key distribution (CV-MDI-QKD) protocol. We report that single and two mode PAS state as well as two mode PR state outperform pure state protocol in the low squeezing and high noise regime. Single mode PAS state and two mode PAS state showed significant resilience to excess noise and offered a longer transmission distance when compared to pure and PR state CV-MDI protocol. Additionally we show that states with higher logarithmic negativity are not necessarily the best choice when used in CV-MDI-QKD.

quant-ph

Optimal Control of Traffic Signals using Quantum Annealing

Quadratic unconstrained binary optimization (QUBO) is the mathematical formalism for phrasing and solving a class of optimization problems that are combinatorial in nature. Due to their natural equivalence with the two dimensional Ising model for ferromagnetism in statistical mechanics, problems from the QUBO class can be solved on quantum annealing hardware. In this paper, we report a QUBO formatting of the problem of optimal control of time-dependent traffic signals on an artificial grid-structured road network so as to ease the flow of traffic, and the use of D-Wave Systems' quantum annealer to solve it. Since current-generation D-Wave annealers have a limited number of qubits and limited inter-qubit connectivity, we adopt a hybrid (classical/quantum) approach to this problem. As traffic flow is a continuous and evolving phenomenon, we address this time-dependent problem by adopting a workflow to generate and solve multiple problem instances periodically.

quant-ph

Interferometrically estimating a quadratic form for any immanant of a matrix and its permutations

We devise a multiphoton interferometry scheme for sampling a quadratic function of a specific immanant for any submatrix of a unitary matrix and its row permutations. The full unitary matrix describes a passive, linear interferometer, and its submatrix is used when photons enter in and are detected at subsets of possible input and output channels. Immanants are mathematical constructs that interpolate between the permanent and determinant; contrary to determinants and permanents, which have meaningful physical applications, immanants are devoid of physical meaning classically but here are shown to be meaningful in a quantum setting. Our quadratic form of immanants is sampled by injecting vacuum and single photons into interferometer input ports such that the photon arrival times are entangled, in contrast to previous methods that control arrival times without entangling. Our method works for any number of photons, and we solve explicitly the quadratic form for the two-, three- and four-photon cases.

quant-ph

Long-distance quantum key distribution using concatenated entanglement swapping with practical resources

We present our approach for sharing photons and assessing resultant four-photon visibility between two distant parties using concatenated entanglement swapping. In addition we determine the corresponding key generation rate and the quantum bit-error rate. Our model is based on practical limitations of resources, including multipair parametric down-conversion sources, inefficient detectors with dark counts and lossy channels. Through this approach, we have found that a trade-off is needed between experimental run-time, pair-production rate and detector efficiency. Concatenated entanglement swapping enables huge distances for quantum key-distribution but at the expense of low key generation rate.

quant-ph

Practical long-distance quantum key distribution through concatenated entanglement swapping with parametric down-conversion sources

We develop a theory for long-distance quantum key distribution based on concatenated entanglement swapping using parametric down-conversion sources and show numerical results of our model. The model incorporates practical resources including multi-pair sources, inefficient detectors with dark counts and lossy channels. We calculate the maximum secret key-generation ratefor up to three entanglement swapping stations by optimizing over resource parameters, and our numerical simulation shows that the range of quantum key distribution can in principle be markedly increased but at the expense of an atrociously unfeasible secret key-generation rate; however, the upper bound of our key rates closely approach the Takeoka-Guha-Wilde upper bound. Our analysis demonstrates the need for new technology such as quantum memory to synchronize photons and our methods should serve as a valuable component for accurately modelling quantum-memory-based long-distance quantum key distribution.

quant-ph

Practical Quantum Teleportation of an Unknown Quantum State

We develop a theory to teleport an unknown quantum state using entanglement between two distant parties. Our theory takes into account experimental limitations due to contribution of multi-photon pair production of parametric down conversion source, inefficiency and dark counts of detectors and channel losses. We use a linear optics setup for quantum teleportation of an unknown quantum state by performing Bell state measurement by the sender. Our theory successfully provides a model for experimentalists to optimize the fidelity by adjusting the experimental parameters. We apply our model to a recent experiment on quantum teleportation and the results obtained by our model are in good agreement with the experiment results.

quant-ph

Long Distance Cavity Entanglement by Entanglement Swapping Using Atomic Momenta

We propose a simple technique to generate entanglement between distant cavities by using entanglement swapping involving atomic momenta. For the proposed scheme, we have two identical atoms, both initially in their ground state, each incident on far apart cavities with particular initial momenta. The two cavities are prepared initially in superposition of zero and one photon state. First, we interact each atom with a cavity in dispersive way. The interaction results into atom-field entangled state. Then we perform EPR state measurement on both atomic momenta state which is an analog of Bell measurement. The EPR state measurement is designed by passing the atoms through cavity beam splitters which transfers the atomic momentum state into superposition state. Finally, these atoms are detected by the detector. After the detection of the atoms, we can distinguish that cavities in one of the Bell states. This process leads to two distant cavity fields entanglement.

quant-ph

Long-distance quantum communication through any number of entanglement swapping operations

We develop a theory and accompanying mathematical model for quantum communication via any number of intermediate entanglement swapping operations and solve numerically for up to three intermediate entanglement swapping operations. Our model yields two-photon interference visibilities post-selected on photon counts at the intermediate entanglement-swapping stations. Realistic experimental conditions are accommodated through parametric down-conversion rate, photon-counter efficiencies and dark-count rates, and instrument and transmission losses. We calculate achievable quantum communication distances such that two-photon interference visibility exceeds the Bell-inequality threshold.

quant-ph

Practical long-distance quantum communication using concatenated entanglement swapping

We construct a theory for long-distance quantum communication based on sharing entanglement through a linear chain of $N$ elementary swapping segments of length~$L=Nl$ where $l$ is the length of each elementary swap setup. Entanglement swapping is achieved by linear optics, photon counting and post-selection, and we include effects due to multi-photon sources, transmission loss and detector inefficiencies and dark counts. Specifically we calculate the resultant four-mode state shared by the two parties at the two ends of the chain, and we derive the two-photon coincidence rate expected for this state and thereby the visibility of this long-range entangled state. The expression is a nested sum with each sum extending from zero to infinite photons, and we solve the case $N=2$ exactly for the ideal case (zero dark counts, unit-efficiency detectors and no transmission loss) and numerically for $N=2$ in the non-ideal case with truncation at $n_\text{max}=3$ photons in each mode. For the general case, we show that the computational complexity for the numerical solution is $n_\text{max}^{12N}$.

quant-ph

Postponement of dark-count effects in practical quantum key-distribution by two-way post-processing

The influence of imperfections on achievable secret-key generation rates of quantum key distribution protocols is investigated. As examples of relevant imperfections, we consider tagging of Alice's qubits and dark counts at Bob's detectors, while we focus on a powerful eavesdropping strategy which takes full advantage of tagged signals. It is demonstrated that error correction and privacy amplification based on a combination of a two-way classical communication protocol and asymmetric Calderbank-Shor-Steane codes may significantly postpone the disastrous influence of dark counts. As a result, the distances are increased considerably over which a secret key can be distributed in optical fibres reliably. Results are presented for the four-state, the six-state, and the decoy-state protocols.

quant-ph

Quantum Nondemolition State Measurement via Atomic Scattering in Bragg Regime

We suggest a quantum nondemolition scheme to measure a quantized cavity field state using scattering of atoms in general Bragg regime. Our work extends the QND measurement of a cavity field from Fock state, based on first order Bragg deflection [9], to any quantum state based on Bragg deflection of arbitrary order. In addition a set of experimental parameters is provided to perform the experiment within the frame work of the presently available technology.

quant-ph

Entanglement between external degrees of freedom of atoms via Bragg deflection

We suggest that atoms undergoing Bragg deflection from a cavity field introduce entanglement between their external degrees of freedom. The atoms interact with an electromagnetic cavity field which is far detuned from atomic transition frequency and is in superposition state. We provide a set of experimental parameters in order to perform the suggested experiment within the frame work of the presently available technology.

quant-ph