arXiv subjects

Mehmet Emre Tasgin

Publications and source records attributed to Mehmet Emre Tasgin.

At least 19 recordsLinked to original sources

arXiv2026

Electrically-programmable frequency comb for compact quantum photonic circuits

Recent efforts have demonstrated the first prototypes for compact and programmable photonic quantum computers (PQCs). Utilization of time-bin encoding in loop-like architectures enabled programmable generation of quantum states and execution of different (programmable) logic gates on a single circuit. Actually, there is still space for better compactness and complexity of available quantum states and gate operations: a photonic circuit (PC) can operate at multiple frequencies. Here, we propose an electrically-programmable frequency comb that generates continuously tunable entanglement among different frequencies. The device is not directly integrated into fragile quantum processing components but is to be used as a fast (picoseconds) tunable auxiliary source provided into state-of-the-art measurement-induced loop-based photonic quantum computers employing programmable (50 MHz) beam-splitters (BSs) and phase-shifters. Multimode entanglement generation is controlled via Fano resonance in the nonlinear response. The generated entanglement can be tuned continuously via an applied voltage which can be delivered to the device via nm-thick wires. The proposed device is integrable, CMOS-compatible, and operates below ps but is limited with transistor clock speeds 5-100 GHz.

quant-ph↗

arXiv2026

All-optical switching of continuous-variable entanglement in an absorption-suppressed plasmonic nanodimer

A subwavelength quantum-photonic circuit element should simultaneously generate nonclassical light, suppress plasmonic loss, and remain dynamically tunable. We show that an orthogonal plasmonic nanorod dimer can satisfy all three requirements. A phase-locked control polarization induces plasmonic refractive-index enhancement, driving the probe response toward a near-zero-extinction regime while simultaneously tuning the local second-harmonic parametric interaction. The resulting nonlinear plasmonic source operates in an absorption-suppressed regime and enables all-optical control of quantum correlations. We demonstrate switchable logarithmic negativity and single-mode nonclassicality, establishing a route toward actively tunable quantum-plasmonic circuit elements operating well below the diffraction limit.

quant-ph↗

arXiv2026

Encoding classical data into the squeezing of noisy-states for plasmonic communication

Surface plasmon polaritons (SPPs) are known to preserve quantum optical properties --such as squeezing-- over distances far exceeding those of classical field amplitudes. However, the surviving squeezing typically becomes so weak that its detection requires prohibitively large numbers of measurements. Here we introduce a fundamentally new paradigm for plasmonic communication in which nonclassicality itself carries the information. We (i) encode classical data (bits or dits) directly into the {\it degree of nonclassicality} (e.g., squeezing) of SPPs, thereby enabling information transfer over distances where classical amplitude encoding fails. We further (ii) show that this information can be retrieved from long-lived correlations generated at the readout stage via a beam splitter. Crucially, we demonstrate that (iii) encoding on initially noisy states leads to a counterintuitive enhancement: the encoded information remains accessible after long propagation distances using only a few measurements, outperforming both squeezed vacuum and amplitude-based schemes by orders of magnitude. Finally, (iv) in the THz regime --relevant for graphene and carbon-nanotube platforms at room temperature-- we \textit{exploit}, rather than suppress, the intrinsic thermal background, enabling robust, high-bandwidth nanoscale communication.

quant-ph↗

arXiv2026

Anatomy of entanglement and nonclassicality criteria

We examine the internal structure of two-mode entanglement criteria for quadrature- and number-phase-squeezed states. For criteria obtained from the partial transpose of the Schrödinger--Robertson inequality, we show that the additional covariance term effectively performs an optimization over the intra-mode rotations entering the criterion. We demonstrate this both for quadrature variables and for number-phase-squeezed states. We further show that Simon's criterion carries out this optimization automatically, which motivates a Simon-like criterion for number-phase-squeezed states that performs the optimization directly in the number-phase plane. We also analyze entanglement in terms of the product of the noises of the two modes, which we call the noise area. Analytically and numerically, we explore whether widely used entanglement criteria can be interpreted as searches for a noise area below unity. In particular, for the product form of the Duan--Giedke--Cirac--Zoller criterion, we show numerically that the minimum noise area obtained after optimization over intra-mode rotations equals the input nonclassicality that a beam splitter needs to generate the same amount of entanglement as the state under consideration. Finally, for Gaussian states we introduce an alternative entanglement measure that can also be extended to multimode settings, and we outline several open questions, including a simpler definition of entanglement depth for number-phase-squeezed states.

quant-ph↗

arXiv2026

Detecting nonclassicality in randomly-displaced copies of a squeezed state

We address a fundamental question: Can one determine whether a received signal is squeezed when each copy arrives with a different displacement/amplitude? We introduce an interaction Hamiltonian that converts quadrature squeezing into number squeezing. Using this conversion, we test whether the copies satisfy $g^{(2)}(0)<1$. The Hamiltonian itself does not create nonclassicality; it only transfers it from quadrature squeezing to number squeezing. This allows us to identify squeezing even when individual copies have random displacements.

quant-ph↗

arXiv2026

Quantum illumination with nonzero-mean signal-idler states via noise-enhanced heterodyne work extraction

Room temperature microwave and low-THz links exhibit large thermal occupations, making phase sensitive signal-idler correlations difficult to recover after loss. We introduce a work-extraction-based quantum-illumination receiver in which the returned mode $\hat{a}_R$ is measured via heterodyne detection and the outcome is fed forward to a locally stored, possibly displaced idler. For a noisy two-mode-squeezed resource, the receiver is characterized by the heterodyne correlation parameter $x_{\rm h}=ηc^2/[a(b+ν_{\rm h})]$. The calibrated displaced-idler work score has Chernoff exponent $ξ_{\rm h}=x_{\rm h}/4+O(x_{\rm h}^2)$, which becomes linear in the target transmissivity $η$ in the weak-return, background-dominated regime, matching the leading-order performance of an ideal OPA receiver, but achieved here via a linear and directly measurable correlation mechanism. Unlike OPA-based schemes, the present protocol does not require zero first moments and does not rely on weak-probability nonlinear detection. In our scheme, extracted work converts hard-to-measure second order moment correlation information into an accessible first moment signal. Moreover, preparation noise $\bar{n}_p$, naturally present at room temperature in the microwave and THz regimes, can be directly harnessed when correlated prior to transmission, whereas a classical coherent signal cannot utilize such incoherent thermal photons without first converting them into usable signal energy.

quant-ph↗

arXiv2025

Off resonant Fano enhanced single molecule resolution imaging with a CW source

Apertureless scanning near-field optical microscopy (a-SNOM) is typically limited to ~10 nm resolution by the tip apex size. We demonstrate that ~1-nm resolution can be achieved under continuous-wave (CW) illumination by exploiting Fano path interference. A defect center that naturally forms at the apex of a metal-coated AFM tip acts as a quantum object and induces Fano interference, forcing a stronger but normally off-resonant plasmonic mode (597 nm) to operate effectively on resonance at the driving wavelength (520 nm). Because this interference occurs only beneath the defect, a ~1-nm-wide, strongly enhanced near-field hotspot is created. Using this off-resonant Fano-enhanced field, we achieve single-molecule-resolution imaging based on exact three-dimensional Maxwell simulations.

physics.optics↗

arXiv2025

Electrical-control of third-order nonlinearity via Fano interference

Programmable photonic computers necessitate the integration of electrically-tunable compact components into the photonic devices. In the state-of-the-art photonic quantum computers~(PQCs), phase-shift and displacement gates can be implemented in an electrically-programmable way. An efficient PQC, however, necessitates also the tuning of third or higher order nonlinearity for implementing continuous-variable~(CV) gates at a shorter sequence. Here, we demonstrate that such an optical component can be designed using Fano interference and Stark effect in a nonlinear nano-plasmonic system. We study the coupling of a broadband bright plasmon mode to a narrow linewidth quantum object(s), QO(s). We show that by shifting the level-spacing of the QO via Stark effect, one can continuously tune the third-order nonlinearity gate within a picosecond response time. We also present finite-difference time domain~(FDTD) simulations that take the retardation effects into account. In addition, we also show that enhancement due to Fano interference degrades if the QOs are positioned randomly as each QO introduces different phases. This reveals the importance of the spatial extent of the QO-ensemble to be employed in the experiments.

physics.optics↗

arXiv2025

Active tuning of ENZ resonances in meta-antenna through phase modulation of optical pulse

Plasmonic nanoantennas offer new avenues to manipulate the propagation of light in materials due to their near field enhancement and ultrafast response time. Here we investigate the epsilon-near-zero (ENZ) response in an L-shaped nanoantenna structure under the phenomenon of plasmonic analog of enhancement in the index of refraction. Using a quantum mechanical approach, we analyze the modulation in the response of probe field and emergence of ENZ frequency region both in the linear and nonlinear plasmonic system. We also demonstrate the active tuning of ENZ frequency region in a nanoantenna structure by modulating the phase of control pulse. The analytical and 3D FDTD simulation results show a significant spectral shift in the ENZ modes. Our proposed method offers the possibility to design and control optical tunable ENZ response in plasmonic metasurfaces without the use of ENZ material. Such metasurfaces can be used in on-chip photonic integrated circuits, further localization of incident fields, slow light operations and various quantum technologies.

physics.app-ph↗

arXiv2025

Observable criterion for collective entanglement in Boson-lattice system

An optical lattice with cold trapped atoms represents a quantum system of fundamental importance as it enables the study of quantum many-body system in a controllable way. It is thus necessary to develop theoretical and experimental tools to explore quantum correlation in such systems to advance our understanding of many-body physics. While previous works have identified some profound aspects of quantum entanglement using e.g. entanglement entropy, there exists a critical demand to have an experimentally accessible tool to investigate many-body quantum entanglement in a broad context. We present an entanglement criterion characterizing collective entanglement in Boson lattice systems and enabling experimental observation readily. On applying our approach to the extended Bose-Hubbard model, we show that our criterion witnesses phase transitions such as Mott insulator--superfluid and Mott insulator--charge density wave transitions. Remarkably, it also makes it possible to detect multipartite entanglement among boson lattice sites in a rigorous sense. Our criterion can be experimentally tested via Raman scattering or time-of-flight methods, which are within the reach of current technology.

quant-ph↗

arXiv2025

Optically tunable linear and nonlinear enhancement of index of refraction

Control of optical properties of materials by tuning their refractive index can revolutionize the current state-of-the-art technology to manipulate light propagation in the high loss media. Here we demonstrate active optical tuning of the plasmonic analog of \textit{enhancement of index of refraction} (EIR) in both linear and nonlinear regimes using a quantum mechanical approach. By employing a pump-probe scheme, we investigate the tuning of refractive index of the probe field by varying amplitude and phase of the pump source. In contrast to classical approach used in \cite{Panahpour2019}, we formulate both first- and second-order quantization to analyze nonlinear enhancement in the refractive index by modulating the response function of probe field. This approach enables indirect tuning of nonlinear modes and coherent control of the probe pulse under the coupling of linear plasmonic modes supported by two L-shaped nano-ellipsoids. Varying the pump amplitude not only shows a significant enhancement in the EIR in both regimes but also effectively suppresses optical losses with zero dispersion at the system's resonance frequency. Additionally, tuning pump phase induces a spectral shift in the frequency of the probe field which open new ways for active tuning of epsilon-near-zero (ENZ) materials. Our approach offers all-optical tuning of nonlinear refractive index which is essential for quantum technological applications. It also provides coherent control of optical properties of plasmonic nanostructures with applications in loss-compensated propagation and zero-index to high-refractive-index plasmonic metamaterials, as well as photonic switches.

physics.optics↗

arXiv2025

Surface plasmon polaritons with extended lifetime

The propagation distance of surface plasmon polaritons (SPPs) on metal nanowires is severely limited by their short lifetime, primarily due to strong metallic losses. In this work, we show that the lifetime-and thus the propagation distance-of SPPs can be significantly extended through the use of Fano resonances. Our FDTD simulations demonstrate that the SPP intensity at a fixed propagation distance can be enhanced by approximately 30 times. Furthermore, this enhancement factor is multiplicative with improvements achieved through other methods. We emphasize that this result represents only a starting point, as no optimization was performed due to limited computational resources.

physics.optics↗

arXiv2025

Voltage-tunable, femtometer-precision plasmo-mechanical displacement at fixed gap size

We propose an elegant method for continuous electrical-tuning of plasmo-mechanical displacement and squeezing without changing plasmonic gap size. Recent experiments bend the mechanical oscillator (cantilever) in units of nm via electrostatic actuators. We do not bend the cantilever but merely electrically-tune the gap intensity, so plasmo-mechanical coupling, via Fano resonance. This allows continuous displacement tuning in units of mechanical oscillator length that is about 30 fm in the experiments. This way, coupling strength can be tuned by 2 orders-of-magnitude via only a 1 V potential difference. Response time is picoseconds. Moreover, quadrature-squeezing (entanglement) of the oscillator can also be tuned continuously.

quant-ph↗

arXiv2024

Voltage-controlled extraordinary optical transmission in the visible regime

Control of components in integrated photonic circuits is crucial in achieving programmable devices. Operation bandwidth of a plasmonic device cannot be generally tuned once it is manufactured, especially in the visible regime. Here, we demonstrate the electrical control of such a device for extraordinary optical transmission~(EOT) in the visible regime. (i) Operation frequency of the EOT device can be tuned via a bias voltage applied through nanowires. (ii) Or, at a given frequency, the EOT signal (normalized to the incident field) can be tuned continuously, e.g., between $10^{-4}$ and $0.4$. This corresponds to a 3-orders of magnitude modulation depth. We utilize Fano resonances induced by a quantum emitter~(QE) that is embedded into the nanoholes. The external bias-voltage tunes QE's resonance. We also discuss the lifetime extensions of surface plasmon polaritons as a response to an ultra-short optical pulse. Our proposed method provides the active electronic control of EOT signal which makes it a feasible and compact element in integrated photonic circuits, for bio-sensing, high resolution imaging, and molecular spectroscopy applications.

physics.optics↗

arXiv2023

Environmental-induced work extraction

A local measurement extracts work as a backaction, e.g., in a system of two entangled cavities: first cavity, $a$, comprises a piston and the measurement is carried out on the second cavity, $b$. When no one makes a measurement on the cavity $b$, i.e., it is simply placed in vacuum; environmental monitoring results in the coherent states as the einselected pointer states (the measurement basis) [PRL 70, 1187 (1993)]. This makes the measurement, that nature itself performs, a Gaussian one with a fixed strength $λ=1$. We show that this makes nature assign a \textit{fixed} amount of work to a particular entanglement degree $0\leq ξ(r) \leq 1$, i.e., $W=ξ(r)\times(\bar{n}\hbarω_a)$, nothing that the term in parenthesis is the entire thermal energy. Afterwards, we show that this phenomenon applies quite generally, i.e, not restricted to a two-cavities system. We also touch on the influence of inherited symmterization entanglement in this context. We can arrive an additional phenomenon by considering that work is simply the process of converting randomly moving microscopic ingredients~(vanishing mean-velocity) into a directional one, i.e, with a nonzero mean-velocity. We show that such a change in the character of the motion introduces curvature in spacetime according to general relativity. This phenomenon is the first demonstration of a quantitative relation between entanglement and curvature using solely the quantum optics arguments.

quant-ph↗

arXiv2023

Energy of the symmetrization entanglement

When a measurement is carried out on one of the entangled parties, the second party can extract work owing to the reduction in its entropy. Here we inquire the amount of work/energy corresponding to the symmetrization entanglement of identical particles (bosons) in a condensate. One measures the quantum state of a particular boson which can be performed only under some certain conditions. We learn that the extracted work comes out to be the \textit{complete} thermodynamical energy present in the condensate. %We learn that the work extracted by the remaining part of the condensate is equal to the excitation energy of the measured boson times the thermodynamical probability of being in the excited state, i.e., $\hbar ω_{eg} \times \exp(-\hbar ω_{eg}/k_BT)$. We study the phenomenon in an interacting Bose-Einstein condensate. Then, we discuss that the results may also have fundamental implications on the pair creation in QED vacuum.

quant-ph↗

arXiv2023

All-Optical Control of Ultrafast Plasmon Resonances in the Pulse-Driven Extraordinary Optical Transmission

Understanding the ultrafast processes at their natural-time scale is crucial for controlling and manipulating nanoscale optoelectronic devices under light-matter interaction. Here, we demonstrate that ultrafast plasmon resonances, attributed to the phenomenon of Extraordinary Optical Transmission (EOT), can be significantly modified by tuning the spectral and temporal properties of the ultrashort light pulse. In this scheme, all-optical active tuning governs spatial and temporal enhancement of plasmon oscillations in the EOT system without device customization. We analyze the spectral and temporal evolution of the system through two approaches. First, we develop a theoretical framework based on the coupled harmonic oscillator model, which analytically describes the dynamics of plasmon modes in the coupled and uncoupled state. Later, we compare the evolution of the system under continuous wave and pulsed illumination. Further, we discuss time-resolved spectral and spatial dynamics of plasmon modes through 3D-FDTD simulation method and wavelet transform. Our results show that optical tuning of oscillation time, intensity, and spectral properties of propagating and localized plasmon modes yields a 3-fold enhancement in the EOT signal. The active tuning of the EOT sensor through ultrashort light pulses pave the way for the development of on-chip photonic devices employing high-resolution imaging and sensing of abundant atomic and molecular systems.

physics.optics↗

arXiv2023

Environmental-induced work extraction

A measurement can extract work from an entangled, e.g., two-mode system. Here, we inquire the extracted work when no intellectual creature, like an ancilla/daemon, is present. When the monitoring is carried out by the environmental modes, that is when no measurement-apparatus is present, the measurement-basis becomes the coherent state. This implies a Gaussian measurement with a fixed strength $λ=1$. For two-mode Gaussian states, extracted work is already independent from the measurement outcome. After the strength is also fixed, this makes nature assign a particular amount of work to a given entanglement degree. Extracted work becomes the entanglement-degree times the entire thermal energy at low temperatures -- e.g., room temperature for optical modes. Environment, nature itself, converts entanglement to an ordered, macroscopic, directional~(kinetic) energy from a disordered, microscopic, randomized thermal energy. And the converted amount is solely determined by the entanglement.

quant-ph↗