arXiv subjects

Jelena Vučković

Publications and source records attributed to Jelena Vučković.

At least 19 recordsLinked to original sources

arXiv2026

Observation of quadrature-dependent unidirectional flow of light

Unidirectional transport of light is a central capability in photonics, enabling critical functionalities such as isolation and routing. Ordinarily, this directionality depends on the mode of light, but not its phase. In this work, we experimentally demonstrate phase-dependent unidirectional transport of light for the first time. Specifically, we realize a system where conjugate quadratures of an optical field decouple and propagate in opposite directions. Our all-optical approach uses multiple pump frequencies in a high-$Q$ nanophotonic micro-resonator to achieve Hamiltonian programming through Kerr nonlinearity. Even though we rely on optical nonlinearity, our approach is not limited to any minimal power requirement on the signal. We demonstrate the ultimate limit of this by measuring the effect of quadrature-dependent transport on vacuum fluctuations. Our approach unlocks a fundamental new capability for controlling light, and can enable previously inaccessible regimes of phase-sensitive directional amplification, sensing, and routing.

physics.optics↗

arXiv2026

Integrated Dual-Resonator Architecture for Telecom Photon-Memory Entanglement

Scalable quantum networks require the efficient generation and storage of entanglement between photonic qubits and quantum memories. Quantum repeaters based on absorptive rare-earth-ion photonic memories offer a promising route toward highly multiplexed quantum networking, but unifying spectrally matched photon sources and quantum memories within a common architecture remains a major challenge. Here we demonstrate an integrated photonic architecture for telecom photon-memory entanglement generation based on dual self-similar silicon carbide microring resonators. Connected by a fiber link, one resonator operates as an entangled photon-pair source, while the other functions as a cavity-enhanced atomic-frequency-comb quantum memory. The memory resonator reaches an ensemble cooperativity of 1.9 after hyperfine initialization and is spectrally matched to the source, enabling storage of entangled telecom photons without spectral modification. We generate and characterize photon-memory entanglement from a quantum interference visibility preserved before and after storage. Harnessing the strong source correlations and the high multimode capacity of the memory, we access high-dimensional entanglement spanning 63 temporal modes, reaching a maximum photon information efficiency of 5.1 Ebits per detected photon and a peak on-chip photon-memory entanglement rate of 5.6 kEbits per second. These results establish a route toward chip-scale quantum networking hardware operating over telecommunications infrastructure.

quant-ph↗

arXiv2026

Quantum sensing with a spin ensemble in a two-dimensional material

Quantum sensing with solid-state spin defects has transformed nanoscale metrology, offering sub-wavelength spatial resolution with exceptional sensitivity to multiple signal types. Maximizing these advantages requires minimizing both the sensor-target separation and the detectable signal threshold. However, leading platforms such as nitrogen-vacancy (NV) centers in diamond suffer from performance degradation near surfaces or in nanoscale volumes, motivating the search for optically addressable spin sensors in atomically thin, two-dimensional (2D) van der Waals materials. Here, we present a comprehensive experimental framework to probe a 2D spin ensemble, including its Hamiltonian, coherent sensing dynamics, and noise environment. Using a central spin system in a hexagonal boron nitride (hBN) crystal, we fully map the hyperfine interactions with proximal nuclear spins, demonstrate switchable magnetic and electric noise sensing, and introduce a method to accurately reconstruct the environmental noise spectrum while explicitly accounting for quantum control imperfections. We achieve a record coherence time of $80~μ\mathrm{s}$ under dynamical decoupling, enabling sub-microtesla AC magnetic sensitivity at a $10~\mathrm{nm}$ target distance. Leveraging the broad opportunities for defect engineering in atomically thin hosts, these results lay the foundation for next-generation quantum sensors with ultrahigh sensitivity, tunable noise selectivity, and versatile functionalities.

quant-ph↗

arXiv2026

Quantum Nanophotonic Interface for Tin-Vacancy Centers in Thin-Film Diamond

The negatively charged tin-vacancy center in diamond (SnV$^-$) is an excellent solid state qubit with optically-addressable transitions and a long electron spin coherence time at elevated ($\sim1.7$ K). However, implementing scalable quantum nodes with high-fidelity optical readout of the electron spin state requires efficient photon emission and collection from the system. In this manuscript, we report a quantum photonic interface for SnV$^-$ centers based on one-dimensional photonic crystal cavities fabricated in diamond thin films. Furthermore, we provide a rigorous description of the spontaneous emission dynamics of our system, taking into account individual contributions from both the C and D transitions of the emitter. This allows for determination of Purcell factors per transition and, by extension, the C/D branching ratio SnV$^{-}$ zero phonon line. We observe quality factors up to $\sim$6000 across this sample, and measure up to a 12-fold lifetime reduction, which translates into a Purcell factor of $F_C=26.2\pm1.5$ for a targeted C transition. By considering the cavity mode polarization alignment with the C and D transition dipole moments, we validate the C/D branching ratio to be $η_{\text{BR}}=0.75\pm0.01$, in line with previous theoretical and experimental findings.

quant-ph↗

arXiv2026

High-Performance Wavelength Division Multiplexers Enabled by Co-Optimized Inverse Design

Wavelength division multiplexers are fundamental to the functioning and performance of integrated photonic circuits, with applications ranging from optical interconnects to sensing and quantum technologies. Current solutions are limited by trade-offs between channel spacing, crosstalk, insertion loss, and device footprint. Here, we develop a novel design approach that co-optimizes inverse-designed wavelength division multiplexers and distributed Bragg gratings to achieve ultra-low crosstalk without compromising insertion loss. We experimentally demonstrate less than -40 dB crosstalk for wavelength channel spacing of 15 nm in foundry-compatible silicon and silicon nitride devices across the telecommunications C- and L-bands. Our design process is highly adaptable, allowing for seamless scaling to a greater number of output channels, different spectral windows, and easy translation across various material platforms.

physics.optics↗

arXiv2026

Inverse design for scalable photonic systems

Over the past two decades, photonic inverse design has emerged as a powerful approach to implement photonic devices with improved performance, or realize new functionalities. While the efforts over the first decade focused on proof of concept devices designed and fabricated in university labs, the focus over the past 5-10 years has shifted towards implementation of scalable photonic systems. This article reviews this recent progress, challenges and new directions in photonics inverse design, thus providing a complementary and updated review of the field. We focus on large scale three dimensional photonic inverse design, including metasurfaces, translation of inverse design to commercial foundries and practical silicon photonics, application of photonic inverse design to different materials systems, wavelengths, and optical effects, and finally new directions such as inverse design of quantum systems.

physics.optics↗

arXiv2026

A general framework for interactions between electron beams and quantum optical systems

We provide a theoretical framework to describe the dynamics of a free-electron beam interacting with quantized bound systems in arbitrary electromagnetic environments. This expands the quantum optics toolbox to incorporate free-electron beams for applications in highly tunable quantum control, imaging, and spectroscopy at the nanoscale. The framework recovers previously studied results and shows that electromagnetic environments can amplify the intrinsically weak coupling between a free-electron and a bound electron to reach previously inaccessible interaction regimes. We leverage this enhanced coupling for experimentally feasible protocols in coherent qubit control and towards the nondestructive readout and projective control of the electron beam's quantum-number statistics. Our framework is broadly applicable to microwave-frequency qubits, optical nanophotonics, cavity quantum electrodynamics, and emerging platforms at the interface of electron microscopy and quantum information.

quant-ph↗

arXiv2026

Single-Chip 1.024 Tb/s Optical Receiver for High-Speed Optical links

Integrated optical transceivers, utilizing wavelength-division-multiplexing, offer a path forward for implementation of compact, high-bandwidth and energy-efficient interconnects for future data centers. Here we report the demonstration of a monolithically integrated optical receiver in 45nm CMOS, where efficient multi-layer optical demultiplexing with capacitive tuning, energy efficient electronics and wideband inverse designed grating couplers enable implementation of a 32-channel receiver chip based on wavelength-division multiplexing. The chip operates at an aggregate data-rate of 1.024 Tb/s with all channels operating simultaneously at a data-rate of 32 Gb/s/channel achieving a record energy efficiency of 71 fJ/b, including the power consumption of both the electronic circuitry and the tuning and control of photonic devices, and a record bandwidth density of 4 Tb/s/mm2. The receiver achieves a bit-error-rate below 1E-12 without requiring equalization, error correction or digital processing. Inverse-designed broadband grating couplers provide efficient, low-loss optical coupling into the chip. An on-chip demultiplexer, composed of Mach-Zehnder interferometers (MZIs) and ring resonators, offers a large channel-to-channel isolation sufficient for error-free operation. Capacitive phase shifters embedded within the ring resonators of the demultiplexer are used for wavelength alignment at a zero static power consumption. MZIs and ring-resonators are periodically selected and autonomously locked to the wavelength of the corresponding optical carrier. The implemented monolithic receiver offers a scalable, energy-efficient and reliable solution for the beyond Tb/s optical interconnects.

physics.optics↗

arXiv2025

Many-Body Entanglement in Solid-State Emitters

The preparation and control of quantum states lie at the heart of quantum information science (QIS). Recent advances in solid-state quantum emitters (QEs) and nanophotonics have transformed the landscape of quantum photonic technologies, enabling scalable generation of quantum states of light and matter. A new frontier in solid-state quantum photonics is the engineering of many-body interactions between QEs and photons to achieve robust coherence and controllable many-body entanglement. These entangled states, including photonic graph and cluster states, superradiant emission, and emergent quantum phases, are promising for quantum computation, sensing, and simulation. However, intrinsic inhomogeneities and decoherence in solid-state platforms pose significant challenges to realize such complex entangled states. This review provides an overview of the fundamental many-body interactions and dynamics at the light-matter interfaces of solid-state QEs, and discusses recent advances in mitigating decoherence and harnessing robust many-body coherence.

quant-ph↗

arXiv2025

Single chip 1 Tb/s optical transmitter with inverse designed input and output couplers

Optical interconnects are essential for data centers and AI systems. Given the limited energy production, ultra-low energy and dense optical interconnects are required to support the exponential growth of AI systems. Here we report the demonstration of a monolithically integrated optical transmitter where use of power efficient architecture and devices such as capacitive tuning of optical structures at zero static power consumption and efficient and wideband inverse designed grating couplers enable implementation of a 32-channel transmitter chip based on wavelength-division multiplexing achieving a record modulation energy efficiency of 32 fJ/b at 5 Gb/s/channel and 106 fJ/b at 32 Gb/s/channel, which includes the tuning of optical devices. Furthermore, a bit-error-rate of 1E-12 was achieved, while all channels are simultaneously operating with an aggregate data-rate of 1.024 Tb/s. The system utilizes 16 carrier wavelengths in the optical C band. The pseudo-random-bit-streams are electrically generated on-chip and used to drive individually wavelength-stabilized 2-section p-n-capacitive micro-ring modulators using integrated energy-efficient high-swing electrical drivers. The low-loss inverse designed grating couplers have -1-dB bandwidth of 25 nm. The chip concurrently achieves the highest aggregate data-rate, the highest energy efficiency and the highest bandwidth density for a multi-channel high date-rate optical transmitter chip reported to date.

physics.optics↗

arXiv2025

Variational processing of multimode squeezed light

Integrated multimode quantum optics is a promising platform for scalable continuous-variable quantum technologies leveraging multimode squeezing in both the spatial and spectral domains. However, on-chip measurement, routing and processing the relevant ``supermodes'' over which the squeezing resource is distributed still scales quadratically with the number of modes $N$, causing rapid increase in photonic circuit size and number of required measurements. Here, we introduce a variational scheme, relying on self-configuring photonic networks (SCN) that learns and extracts the most-squeezed supermodes sequentially, reducing both the circuit size and the experimental overhead. Using homodyne measurement as a cost function, a sparse SCN discovers the $l\ll N$ most significant supermodes using $O(lN)$ physical elements and optimization steps. We analyze and numerically simulate these architectures for both real-space and frequency-domain implementations, showing a fidelity close to unity between the learned circuit and the supermode decomposition, even in the presence of optical losses and detection noise. In the frequency domain, we show that circuit size can be further reduced by using inverse-designed surrogate networks, which emulate the layers learned thus far. Using two different frequency encoding schemes -- uniformly- and non-uniformly-spaced frequency bins -- we reduce an entire network (learning all $N$ supermodes) to $O(N)$ and even $O(1)$ modulated cavities. Our results point toward chip-scale, resource-efficient quantum processing units and demultiplexers for continuous variable processing in multimode quantum optics, with applications ranging from quantum communication, metrology, and computation.

quant-ph↗

arXiv2025

Quantum sensing of electron beams using solid-state spins

Scattering experiments with energetic particles, such as free electrons, have been historically used to reveal the quantum structure of matter. However, realizing coherent interactions between free-electron beams and solid-state quantum systems has remained out of reach, owing to their intrinsically weak coupling. Realizing such coherent control would open up opportunities for hybrid quantum platforms combining free electrons and solid-state qubits for coincident quantum information processing and nanoscale sensing. Here, we present a framework that employs negatively charged nitrogen-vacancy centers (NV-) in diamond as quantum sensors of a bunched electron beam. We develop a Lindblad master equation description of the magnetic free-electron--qubit interactions and identify spin relaxometry as a sensitive probe of the interaction. Experimentally, we integrate a confocal fluorescence microscopy setup into a microwave-bunched electron beam line. We monitor charge-state dynamics and assess their impact on key sensing performance metrics (such as spin readout contrast), defining safe operating parameters for quantum sensing experiments. By performing $T_1$ relaxometry under controlled electron beam exposure, we establish an upper bound on the free-electron--spin coupling strength. Our results establish NV- centers as quantitative probes of free electrons, providing a metrological benchmark for free-electron--qubit coupling under realistic conditions, and chart a route toward solid-state quantum control with electron beams.

quant-ph↗

arXiv2025

Low-Dissipation Nanomechanical Devices from Monocrystalline Silicon Carbide

The applications of nanomechanical resonators range from biomolecule mass sensing to hybrid quantum interfaces. Their performance is often limited by internal material damping, which can be greatly reduced by using crystalline materials. Crystalline silicon carbide is appealing due to its exquisite mechanical, electrical and optical properties, but has suffered from high internal damping due to material defects. Here we resolve this by developing nanomechanical resonators fabricated from bulk monocrystalline 4H-silicon carbide. This allows us to achieve damping as low as 2.7 mHz, more than an order-of-magnitude lower than any previous crystalline silicon carbide resonator and corresponding to a quality factor as high as 20 million at room temperature. The volumetric dissipation of our devices reaches the material limit for silicon carbide for the first time. This provides a path to greatly increase the performance of silicon carbide nanomechanical resonators.

cond-mat.mes-hall↗

arXiv2025

Mesoscopic cavity quantum electrodynamics with phase-disordered emitters in a Kerr nonlinear resonator

The field of cavity quantum electrodynamics (QED) has seen a recent resurgence of interest in few- and many-body physics owing to the realization that the breaking of symmetries and the presence of disorder can give rise to entirely new phenomena. Here we demonstrate a few-emitter cavity QED system capable of realizing new Hamiltonians in quantum optics based on breaking of symmetries and the realization of an in situ Kerr nonlinearity. Our experiment relies on a high-finesse silicon carbide whispering gallery mode resonator hosting an ensemble of silicon vacancy color centers. The simultaneous presence of spectral and spatial disorder of the mesoscopic atom system gives rise to emergent chirality, and the optical nonlinearity of the silicon carbide host crystal enables the observation of atom-photon correlations induced by a four-photon nonlinear process. This work demonstrates the potential for solid state defect systems to realize emerging proposals and to study fundamental physics in quantum electrodynamics.

quant-ph↗

arXiv2025

Quantum critical electro-optic and piezo-electric nonlinearities

Electro-optics, the tuning of optical properties of materials with electric fields, is key to a multitude of quantum and classical photonics applications. However, a major obstacle preventing many emerging use cases is inefficient modulation in cryogenic environments, as traditional tuning mechanisms degrade at low temperatures. Guided by the connection between phase transitions and nonlinearity, we identify the quantum paraelectric perovskite SrTiO$_3$ (STO) as the strongest cryogenic electro-optic photonic material. As a result of the unique quantum paraelectric phase of STO, we demonstrate a dynamically tunable linear Pockels coefficient ($r_{33}$) exceeding 500 pm/V at $T=5$ K, and study its full temperature and bias dependence. We also measure an enhanced piezo-electric coefficient ($d_{33}$) above 90 pC/N. Both of these coefficients exceed all previously reported values for cryogenic materials, including lithium niobate ($r_{33}\approx24$ pm/V) and barium titanate ($r_{42}\approx170$ pm/V). Furthermore, by tuning STO towards \textit{quantum criticality} with oxygen isotope substitution we more than double the optical and piezo-electric nonlinearities, demonstrating a linear Pockels coefficient above 1100 pm/V. Our results probe the link between quantum phase transitions, dielectric susceptibility, and optical nonlinearities, unlocking opportunities in cryogenic optical and mechanical systems, and provide a framework for discovering new nonlinear materials.

cond-mat.mtrl-sci↗

arXiv2024

Cavity Quantum Electrodynamics in Finite-Bandwidth Squeezed Reservoir

Light-matter interaction with squeezed vacuum has received much interest for the ability to enhance the native interaction strength between an atom and a photon with a reservoir assumed to have an infinite bandwidth. Here, we study a model of parametrically driven cavity quantum electrodynamics (cavity QED) for enhancing light-matter interaction while subjected to a finite-bandwidth squeezed vacuum drive. Our method is capable of unveiling the effect of relative bandwidth as well as squeezing required to observe the anticipated anti-crossing spectrum and enhanced cooperativity without the ideal squeezed bath assumption. Furthermore, we analyze the practicality of said models when including intrinsic photon loss due to resonators imperfection. With these results, we outline the requirements for experimentally implementing an effectively squeezed bath in solid-state platforms such as InAs quantum dot cavity QED such that \textit{in situ} control and enhancement of light-matter interaction could be realized.

quant-ph↗

arXiv2024

Quantum sensitivity of parametric oscillators

Many quantum systems exhibit high sensitivity to their initial conditions, where microscopic quantum fluctuations can significantly influence macroscopic observables. Understanding how quantum states may influence the behavior of nonlinear dynamic systems may open new avenues in controlling light-matter interactions. To explore this issue, we analyze the sensitivity of a fundamental quantum optical process - parametric oscillation - to quantum initializations. Focusing on optical parametric oscillators (OPOs), we demonstrate that the quantum statistics of arbitrary initial states are imprinted in the early-stage dynamics and can persist in the steady-state probabilities. We derive the "quantum sensitivity" of parametric oscillators, linking the initial quantum state to the system's steady-state outcomes, highlighting how losses and parametric gain govern the system's quantum sensitivity. Moreover, we show that these findings extend beyond OPOs to a broader class of nonlinear systems, including Josephson junction based superconducting circuits. Our work opens the way to a new class of experiments that can test the sensitivity of macroscopic systems to quantum initial conditions and offers a pathway for controlling systems with quantum degrees of freedom.

quant-ph↗

arXiv2024

Unified laser stabilization and isolation on a silicon chip

Rapid progress in photonics has led to an explosion of integrated devices that promise to deliver the same performance as table-top technology at the nanoscale; heralding the next generation of optical communications, sensing and metrology, and quantum technologies. However, the challenge of co-integrating the multiple components of high-performance laser systems has left application of these nanoscale devices thwarted by bulky laser sources that are orders of magnitude larger than the devices themselves. Here we show that the two main ingredients for high-performance lasers -- noise reduction and isolation -- currently requiring serial combination of incompatible technologies, can be sourced simultaneously from a single, passive, CMOS-compatible nanophotonic device. To do this, we take advantage of both the long photon lifetime and the nonreciprocal Kerr nonlinearity of a high quality factor silicon nitride ring resonator to self-injection lock a semiconductor laser chip while also providing isolation. Additionally, we identify a previously unappreciated power regime limitation of current on-chip laser architectures which our system overcomes. Using our device, which we term a unified laser stabilizer, we demonstrate an on-chip integrated laser system with built-in isolation and noise reduction that operates with turnkey reliability. This approach departs from efforts to directly miniaturize and integrate traditional laser system components and serves to bridge the gap to fully integrated optical technologies.

physics.optics↗