arXiv subjects

P. A. Ameen Yasir

Publications and source records attributed to P. A. Ameen Yasir.

7 recordsLinked to original sources

arXiv2026

Compactifying linear optical unitaries using multiport beamsplitters

We show that any $N$-dimensional unitary matrix can be realized using a finite sequence of concatenated identical fixed multiport beamsplitters (MBSs) and phase shifters (PSs). Our construction is based on a Lie group theorem applied to existing decompositions. Using the Bell-Walmsley-Clements framework, we prove that any $N$-dimensional unitary requires $N+2$ phase masks, $N-1$ fixed MBSs, and $N-1$ BSs. Our scheme requires only $\mathcal{O}(N)$ fixed, identical components (MBSs and BSs) compared to the $\mathcal{O}(N^2)$ fixed BSs required by conventional schemes (e.g., Clements), all while keeping the same number of PSs. Experimentally, these MBS can be realized as a monolithic element via femtosecond laser writing, offering superior performance through reduced insertion losses. As an application, we present a reconfigurable linear optical circuit that implements a three-dimensional unitary emerging in the unambiguous discrimination of two nonorthogonal qubit states.

quant-ph↗

arXiv2025

Tripartite multiphoton Jaynes-Cummings model: Analytical solution and Wigner nonclassicalities

We investigate a generic tripartite quantum system featuring a single qubit interacting concurrently with two quantized harmonic oscillators via nonlinear multiphoton Jaynes-Cummings (MPJC) interactions. Assuming the qubit is initially prepared in a superposition state and the two oscillators are in arbitrary Fock states, we analytically trace the temporal evolution of this tripartite pure initial state. We identify four broad cases, each further divided into two subcases, and derive exact analytical solutions for most cases. Notably, we obtain perfect transfer of excitations between the oscillators by carefully selecting system parameters. In addition, we extensively examine the manner in which the nonclassicalities of various initial oscillator Fock states, quantified by the volume of negative regions in the associated Wigner functions, evolve under the MPJC Hamiltonian, considering diverse system parameters including environmental effects. Besides producing substantial enhancements in the initial value for higher photon number states, our analysis reveals that driven solely by the initial qubit energy, with both oscillators initialized in the vacuum state, the nonlinear MPJC interaction yields a significant amount of nontrivial Wigner negativity in the oscillators. The additional nonlinearity introduced by the multiphoton process plays a pivotal role in surpassing the initial nonclassicalities of the photon number states.

quant-ph↗

arXiv2024

Genuine non-Gaussian entanglement of light and quantum coherence for an atom from noisy multiphoton spin-boson interactions

Harnessing entanglement and quantum coherence plays a central role in advancing quantum technologies. In quantum optical light-atom platforms, these two fundamental resources are often associated with a Jaynes-Cummings model description describing the coherent exchange of a photon between an optical resonator mode and a two-level spin. In a generic nonlinear spin-boson system, more photons and more modes will take part in the interactions. Here we consider such a generalization -- the two-mode multiphoton Jaynes-Cummings (MPJC) model. We demonstrate how entanglement and quantum coherence can be optimally generated and subsequently manipulated in experimentally accessible parameter regimes. A detailed comparative analysis of this model reveals that nonlinearities within the MPJC interactions produce genuinely non-Gaussian entanglement, devoid of Gaussian contributions, from noisy resources. More specifically, strong coherent sources may be replaced by weaker, incoherent ones, significantly reducing the resource overhead, though at the expense of reduced efficiency. At the same time, increasing the multiphoton order of the MPJC interactions expedites the entanglement generation process, thus rendering the whole generation scheme again more efficient and robust. We further explore the use of additional dispersive spin-boson interactions and Kerr nonlinearities in order to create spin coherence solely from incoherent sources and to enhance the quantum correlations, respectively. As for the latter, somewhat unexpectedly, there is not necessarily an increase in quantum correlations due to the augmented nonlinearity. Towards possible applications of the MPJC model, we show how, with appropriately chosen experimental parameters, we can engineer arbitrary NOON states as well as the tripartite W state.

quant-ph↗

arXiv2023

Quantum direct communication protocol using recurrence in k-cycle quantum walk

The ability of quantum walks to evolve in a superposition of distinct quantum states has been used as a resource in quantum communication protocols. Under certain settings, the $k$-cycle discrete-time quantum walks\,(DTQW) are known to recur to its initial state after every $t_r$ steps. We first present a scheme to optically realize any $k$-cycle DTQW using $J$-plate, orbital angular momentum\,(OAM) sorters, optical switch, and optical delay line. This entangles the polarization and OAM degrees of freedom\,(DoF) of a single photon. Making use of this recurrence phenomena of $k$-cycle DTQW and the entanglement generated during the evolution, we present a new quantum direct communication protocol. The recurrence and entanglement in $k$-cycle walk are effectively used to retrieve and secure the information, respectively, in the proposed protocol. We investigate the security of the protocol against intercept and resend attack. We also quantify the effect of amplitude damping and depolarizing noises on recurrence and mutual information between polarization and OAM DoF of a single photon.

quant-ph↗

arXiv2023

Optical realization of one-dimensional generalized split-step quantum walks

Quantum walks are more than tools for building quantum algorithms. They have been used effectively to model and simulate quantum dynamics in many complex physical processes. Particularly, a variant of discrete-time quantum walk known as split-step quantum walk is closely related to Dirac cellular automata and topological insulators whose realizations rely on position-dependent control of evolution operators. Owing to the ease of manipulating multiple degrees of freedom of photons, we provide an optical setup of split-step operators which in combination with position-dependent coin (PDC) operation can accomplish a table-top setup of generalized split-step walks. Also, we propose an optical implementation for PDC operation that allows, for instance, to realize electric quantum walks, control localization dynamics, and emulate space-time curvature effects. In addition, we propose a setup to realize {\it any} $t$-step split-step quantum walk involving 2 $J$-plates, 2 variable waveplates, a half-waveplate, an optical switch, and an optical delay line.

quant-ph↗

arXiv2022

Generation of hyperentangled states and two-dimensional quantum walks using $J$- ($q$)- plates and polarization beamsplitters

A single photon can be made to entangle simultaneously in its different internal degrees of freedom (DoF) -- polarization, orbital angular momentum (OAM), and frequency -- as well as in its external DoF -- path. Such entanglement in multiple DoF is known as hyperentanglement and provide additional advantage for quantum information processing. We propose a passive optical setup using $q$-plates and polarization beamsplitters to hyperentangle an incoming single photon in polarization, OAM, and path DoF. By mapping polarization DoF to a two-dimensional coin state, and path and OAM DoF to two spatial dimensions, $x$ and $y$, we present a scheme for realization of two-dimensional discrete-time quantum walk using only polarization beamsplitters and $q$-plates ensuing the generation of hyperentangled states. The amount of hyperentanglement generated is quantified by measuring the entanglement negativity between any two DoF. We further show the hyperentanglement generation can be controlled by using an additional coin operation or by replacing the $q$-plate with a $J$-plate.

quant-ph↗

arXiv2020

Polarization selective Dove prism

We propose a passive all optical device capable of transforming the orbital angular momentum (OAM) state of light conditioned over the polarization states. The efficiency of this device is ensured due to its linear optical nature. As applications of this device, we show CNOT and SWAP operations between polarization and OAM qubits, non-interferometric OAM mode sorter and generalized Pauli X operation on a four-dimensional subspace of OAM.

quant-ph↗