arXiv subjects

Alberto M. Marino

Publications and source records attributed to Alberto M. Marino.

At least 19 recordsLinked to original sources

arXiv2026

Real-time heralded non-Gaussian teleportation resource-state generator

Quantum teleportation is a fundamental quantum communications primitive that requires an entangled resource state. In the continuous-variable regime, non-Gaussian entangled resources have been shown theoretically to improve teleportation fidelity compared to Gaussian squeezed vacuum. We experimentally demonstrate a heralded two-mode resource state for non-Gaussian teleportation capable of real-time use. We characterize this state with two-mode homodyne tomography showing it has fidelity $F=0.973\pm 0.005$ with the expected resource state. Real-time use is enabled by a photon-subtraction orchestrator system performing live coincidence detection and outputting low-jitter and low-latency heralding signals. Live collection of real-time quadrature measurements of photon-subtracted states is enabled by the development of a synchronized homodyne detection server, where the orchestrator system queries the server to collect the real-time quadrature samples corresponding to the heralded state. These results demonstrate significant advancement in enabling the use of heralded non-Gaussian states in quantum networking protocols, especially in the context of quantum repeaters, non-Gaussian quantum sensing, and measurement-based quantum computing.

quant-ph↗

arXiv2025

Mechanical Sensors for Ultraheavy Dark Matter Searches via Long-range Forces

Dark matter candidates with masses around the Planck-scale are theoretically well-motivated, and it has been suggested that it might be possible to search for dark matter solely via gravitational interactions in this mass range. In this work, we explore the pathway towards searching for dark matter candidates with masses around the Planck-scale using mechanical sensors while considering realistic experimental constraints, and develop analysis techniques needed to conduct such searches. These dark matter particles are expected to leave tracks as their signature in mechanical sensor arrays, and we show that we can effectively search for such tracks using statistical approaches to track-finding. We analyze a range of possible experimental setups and compute sensitivity projections for searches for ultraheavy dark matter coupling to the Standard Model via long-range forces. We find that while a search for Planck-scale dark matter purely via gravitational couplings would be exceedingly difficult, requiring $\sim 80\,\mathrm{dB}$ of quantum noise reduction with a $100^3$ array of devices, there is a wide range of currently unexplored dark matter candidates which can be searched for with already existing or near-term experimental platforms.

hep-ph↗

arXiv2025

Light Storage and Retrieval in an Atomic Tripod System

Highly-efficient quantum memories are essential for advancing quantum information processing technologies, including scalable quantum computing and quantum networks. We experimentally demonstrate a light storage and retrieval protocol in a tripod system using an ensemble of laser-cooled $^{87}$Rb atoms. The tripod system, which consists of three ground states and an excited state, offers rich dynamics: its use to coherently store and retrieve a weak probe pulse in the $^{87}$Rb $F=1$ ground state manifold leads to the interference of two spin-wave excitations during storage time that translate to an interference in the peak intensity of the retrieved probe pulse. Our work shows that these interferences, which manifest when varying the pulse sequence or energy level structure, can be controlled experimentally by varying the storage time, optical phase, and magnetic field strength. Theoretical simulations exhibit excellent agreement with the experimental results. This work demonstrates the rich dynamics and versatile capabilities of atomic tripod systems for light storage and retrieval, with key advantages over conventional $Λ$-systems, highlighting the potential of atomic tripod systems for applications in quantum information processing, quantum synchronization, and atomic memory protocols.

quant-ph↗

arXiv2025

Compact Fiber-Coupled Narrowband Two-Mode Squeezed Light Source

Quantum correlated states of light, such as squeezed states, are a fundamental resource for the development of quantum technologies, as they are needed for applications in quantum metrology, quantum computation, and quantum communications. It is thus critical to develop compact, efficient, and robust sources to generate such states. Here we report on a compact, narrowband, fiber-coupled source of two-mode squeezed states of light at 795 nm based on four wave mixing (FWM) in a $^{85}$Rb atomic vapor. The source is designed in a small modular form factor, with two input fiber-coupled beams, the seed and pump beams required for the FWM, and two output fibers, one for each of the modes of the squeezed state. The system is optimized for low pump power (135 mW) to achieve a maximum intensity-difference squeezing of 4.4 dB after the output fibers at an analysis frequency of 1 MHz. The narrowband nature of the source makes it ideal for atomic-based quantum sensing and quantum networking configurations that rely on atomic quantum memories. Such a source paves the way for a versatile and portable platform for applications in quantum information science.

quant-ph↗

arXiv2025

Combining quantum noise reduction resources: a practical approach

Optomechanical sensors are capable of transducing external perturbations to resolvable optical signals. A particular regime of interest is that of high-bandwidth force detection, where an impulse is delivered to the system over a short period of time. Exceedingly sensitive impulse detection has been proposed to observe very weak signals like those due to long range interactions with dark matter that require much higher sensitivities than current sensors can provide. Quantum resources to go beyond the traditional standard quantum limit of these sensors include squeezing of the light used to transduce the signal, backaction evasion by measuring the optimal quadrature, and quantum non-demolition (QND) measurements that reduce backaction directly. These methods have been developed in the context of gravitational wave detection for target frequencies in the audio band range. Here, we provide the theoretical limits to quantum noise reduction for higher and broader frequency targets, such as those from dark matter signals, while combining quantum enhanced readout techniques based on squeezed light and QND measurements with optomechanical sensors. We demonstrate that backaction evasion through QND techniques dramatically reduces the technical challenges presented when using squeezed light for broadband force detection, paving the way for combining multiple quantum noise reduction techniques for enhanced sensitivity in the context of impulse metrology.

quant-ph↗

arXiv2025

Variational optical phase learning on a continuous-variable quantum compiler

Quantum process learning is a fundamental primitive that draws inspiration from machine learning with the goal of better studying the dynamics of quantum systems. One approach to quantum process learning is quantum compilation, whereby an analog quantum operation is digitized by compiling it into a series of basic gates. While there has been significant focus on quantum compiling for discrete-variable systems, the continuous-variable (CV) framework has received comparatively less attention. We present an experimental implementation of a CV quantum compiler that uses two mode-squeezed light to learn a Gaussian unitary operation. We demonstrate the compiler by learning a parameterized linear phase unitary through the use of target and control phase unitaries to demonstrate a factor of 5.4 increase in the precision of the phase estimation and a 3.6-fold acceleration in the time-to-solution metric when leveraging quantum resources. Our results are enabled by the tunable control of our cost landscape via variable squeezing, thus providing a critical framework to simultaneously increase precision and reduce time-to-solution.

quant-ph↗

arXiv2025

Robust Mølmer-Sørensen gate for neutral atoms using rapid adiabatic Rydberg dressing

The Rydberg blockade mechanism is now routinely considered for entangling qubits encoded in clock states of neutral atoms. Challenges towards implementing entangling gates with high fidelity include errors due to thermal motion of atoms, laser amplitude inhomogeneities, and imperfect Rydberg blockade. We show that adiabatic rapid passage by Rydberg dressing provides a mechanism for implementing two-qubit entangling gates by accumulating phases that are robust to these imperfections. We find that the typical error in implementing a two-qubit gate, such as the controlled phase gate, is dominated by errors in the single atom light shift, and that this can be easily corrected using adiabatic dressing interleaved with a simple spin echo sequence. This results in a two-qubit Mølmer-Sørenson gate. A gate fidelity $\sim 0.995$ is achieveable with modest experimental parameters and a path to higher fidelities is possible for Rydberg states in atoms with a stronger blockade, longer lifetimes, and larger Rabi frequencies.

quant-ph↗

arXiv2024

Generation of Scalable Genuine Multipartite Gaussian Entanglement with a Parametric Amplifier Network

Genuine multipartite entanglement is a valuable resource in quantum information science, as it exhibits stronger non-locality compared to bipartite entanglement. This non-locality can be exploited in various quantum information protocols, such as teleportation, dense coding, and quantum interferometry. Here, we propose a scheme to generate scalable genuine multipartite continuous-variable entangled states of light using a parametric amplifier network. We verify the presence of genuine quadripartite, hexapartite, and octapartite entanglement through a violation of the positive partial transpose (PPT) criteria. Additionally, we use $α$-entanglement of formation to demonstrate the scalability of our approach to an arbitrary number of $2N$ genuinely entangled parties by taking advantage of the symmetries present in our scheme.

quant-ph↗

arXiv2024

Quantum enhanced distributed phase sensing with a truncated SU(1,1) interferometer

In recent years, distributed quantum sensing has gained interest for a range of applications requiring networks of sensors, from global-scale clock synchronization to high energy physics. In particular, a network of entangled sensors can improve not only the sensitivity beyond the shot noise limit, but also enable a Heisenberg scaling with the number of sensors. Here, using bright entangled twin beams, we theoretically and experimentally demonstrate the detection of a linear combination of two distributed phases beyond the shot noise limit with a truncated SU(1,1) interferometer. We experimentally demonstrate a quantum noise reduction of 1.7 dB and a classical 3 dB signal-to-noise ratio improvement over the separable sensing approach involving two truncated SU(1,1) interferometers. Additionally, we theoretically extend the use of a truncated SU(1,1) interferometer to a multi-phase-distributed sensing scheme that leverages entanglement as a resource to achieve a quantum improvement in the scaling with the number of sensors in the network. Our results pave the way for developing quantum enhanced sensor networks that can achieve an entanglement-enhanced sensitivity.

quant-ph↗

arXiv2023

Parallel Quantum-Enhanced Sensing

Quantum metrology takes advantage of quantum correlations to enhance the sensitivity of sensors and measurement techniques beyond their fundamental classical limit given by the shot noise limit. The use of both temporal and spatial correlations present in quantum states of light can extend quantum-enhanced sensing to a parallel configuration that can simultaneously probe an array of sensors or independently measure multiple parameters. To this end, we use multi-spatial mode twin beams of light, which are characterized by independent quantum-correlated spatial subregions in addition to quantum temporal correlations, to probe a four-sensor quadrant plasmonic array. We show that it is possible to independently and simultaneously measure local changes in refractive index for all four sensors with a quantum enhancement in sensitivity in the range of $22\%$ to $24\%$ over the corresponding classical configuration. These results provide a first step towards highly parallel spatially resolved quantum-enhanced sensing techniques and pave the way toward more complex quantum sensing and quantum imaging platforms.

quant-ph↗

arXiv2022

Information encoding in the spatial correlations of entangled twin beams

The ability to use the temporal and spatial degrees of freedom of quantum states of light to encode and transmit information is crucial for the implementation of a robust and efficient quantum network. In particular, the large dimensionality of the spatial degree of freedom promises to provide significant enhancements; however, such promise has largely been unfulfilled as the necessary level of control over the spatial degree of freedom to encode information remains elusive. Here, we show that information can be encoded in the distribution of the spatial correlations of highly multi-spatial mode entangled bright twin beams. We take advantage of the dependence of the spatial correlations on the angular spectrum of the pump required for four-wave mixing, as dictated by phase matching. The encoded information can be extracted by mapping the momenta distribution of the twin beams to a position distribution in the far field and measuring the spatial cross-correlation of images acquired with a high quantum efficiency electron multiplying charge coupled device. We further show that the encoded information cannot be accessed through individual beam measurements and that the temporal quantum correlations are not modified. We anticipate that the ability to engineer the distribution of the spatial correlations will serve as a novel degree of freedom to encode information and hence provide a pathway for high capacity quantum information channels and networks. In addition, a high degree of control over the spatial properties of quantum states of light will enable real-world quantum-enhanced spatially resolved sensing and imaging applications.

quant-ph↗

arXiv2022

Transmission Estimation at the Fundamental Quantum Cramér-Rao Bound with Macroscopic Quantum Light

The field of quantum metrology seeks to apply quantum techniques and/or resources to classical sensing approaches with the goal of enhancing the precision in the estimation of a parameter beyond what can be achieved with classical resources. Theoretically, the fundamental minimum uncertainty in the estimation of a parameter for a given probing state is bounded by the quantum Cramér-Rao bound. From a practical perspective, it is necessary to find physical measurements that can saturate this fundamental limit and to show experimentally that it is possible to perform measurements with the required precision to do so. Here we perform experiments that saturate the quantum Cramér-Rao bound for transmission estimation over a wide range of transmissions when probing the system under study with a bright two-mode squeezed state. To properly take into account the imperfections in the generation of the quantum state, we extend our previous theoretical results to incorporate the measured properties of the generated quantum state. For our largest transmission level of 84%, we show a 62% reduction over the optimal classical protocol in the variance in transmission estimation when probing with a bright two-mode squeezed state with 8 dB of intensity-difference squeezing. Given that transmission estimation is an integral part of many sensing protocols, such as plasmonic sensing, spectroscopy, calibration of the quantum efficiency of detectors, etc., the results presented promise to have a significant impact on a number of applications in various fields of research.

quant-ph↗

arXiv2021

Fundamental Sensitivity Bounds for Quantum Enhanced Optical Resonance Sensors Based on Transmission and Phase Estimation

Quantum states of light can enable sensing configurations with sensitivities beyond the shot-noise limit (SNL). In order to better take advantage of available quantum resources and obtain the maximum possible sensitivity, it is necessary to determine fundamental sensitivity limits for different possible configurations for a given sensing system. Here, due to their wide applicability, we focus on optical resonance sensors, which detect a change in a parameter of interest through a resonance shift. We compare their fundamental sensitivity limits set by the quantum Cramér-Rao bound (QCRB) based on the estimation of changes in transmission or phase of a probing bright two-mode squeezed state (bTMSS) of light. We show that the fundamental sensitivity results from an interplay between the QCRB and the transfer function of the system. As a result, for a resonance sensor with a Lorentzian lineshape a phase-based scheme outperforms a transmission-based one for most of the parameter space; however, this is not the case for lineshapes with steeper slopes, such as higher order Butterworth lineshapes. Furthermore, such an interplay results in conditions under which the phase-based scheme provides a higher sensitivity than the transmission-based one but a smaller degree of quantum enhancement. We also study the effect of losses external to the sensor on the degree of quantum enhancement and show that for certain conditions probing with a classical state can provide a higher sensitivity than probing with a bTMSS. Finally, we discuss detection schemes, namely optimized intensity-difference and optimized homodyne detection, that can achieve the fundamental sensitivity limits even in the presence of external losses.

quant-ph↗

arXiv2021

Deterministic Generation of Genuine Tri-Partite Hybrid Atom-Photon Entanglement through Dissipation

The ability to deterministically generate genuine multi-partite entanglement is fundamental for the advancement of quantum information science. We show that the interaction between entangled twin beams of light and an atomic ensemble under conditions for electromagnetically induced transparency leads to the generation of genuine hybrid tri-partite entanglement between the two input fields and the atomic ensemble. In such a configuration, the system is driven through dissipation to a steady state given by the hybrid entangled state. To show the presence of the genuine hybrid entanglement, we introduce a new approach to treat the atomic operators that makes it possible to show a violation of a tri-partite entanglement criterion based on the properties of the two optical fields and collective properties of the atomic ensemble. Additionally, we show that while each of the input optical fields does not exhibit single beam quadrature squeezing, as the fields propagate through the atomic medium their individual quadratures can become squeezed and in some cases oscillate between the presence and absence of squeezing. Finally, we propose a technique to characterize the tri-partite entanglement through joint measurements of the fields leaving the atomic medium, making such an approach experimentally accessible.

quant-ph↗

arXiv2021

Effect of Closely-Spaced Excited States on Electromagnetically Induced Transparency

Electromagnetically induced transparency (EIT) is a well-known phenomenon due in part to its applicability to quantum devices such as quantum memories and quantum gates. EIT is commonly modeled with a three-level lambda system due to the simplicity of the calculations. However, this simplified model does not capture all the physics of EIT experiments with real atoms. We present a theoretical study of the effect of two closely-spaced excited states on EIT and off-resonance Raman transitions. We find that the coherent interaction of the fields with two excited states whose separation is smaller than their Doppler broadened linewidth can enhance the EIT transmission and broaden the width of the EIT peak. However, a shift of the two-photon resonance frequency for systems with transitions of unequal dipole strengths leads to a reduction of the maximum transparency that can be achieved when Doppler broadening is taken into account even under ideal conditions of no decoherence. As a result, complete transparency cannot be achieved in a vapor cell. Only when the separation between the two excited states is of the order of the Doppler width or larger can complete transparency be recovered. In addition, we show that off-resonance Raman absorption is enhanced and its resonance frequency is shifted. Finally, we present experimental EIT measurements on the D1 line of $^{85}$Rb that agree with the theoretical predictions when the interaction of the fields with the four levels is taken into account.

quant-ph↗

arXiv2020

Transmission Estimation at the Cramér-Rao Bound for Squeezed States of Light in the Presence of Loss and Imperfect Detection

Enhancing the precision of a measurement requires maximizing the information that can be gained about the quantity of interest from probing a system. For optical based measurements, such an enhancement can be achieved through two approaches, increasing the number of photons used to interrogate the system and using quantum states of light to increase the amount of quantum Fisher information gained per photon. Here we consider the use of quantum states of light with a large number of photons, namely the bright single-mode and two-mode squeezed states, that take advantage of both of these approaches for the problem of transmission estimation. We show that, in the limit of large squeezing, these states approach the maximum possible quantum Fisher information per photon for transmission estimation that is achieved with the Fock state and the vacuum two-mode squeezed state. Since the bright states we consider can be generated at much higher powers than the quantum states that achieve the maximum quantum Fisher information per photon, they can achieve an much higher absolute precision as quantified by the quantum Cramér-Rao bound. We discuss the effects of losses external to the system on the precision of transmission estimation and identify simple measurements techniques that can saturate the quantum Cramér-Rao bound for the bright squeezed states even in the presence of such external losses.

quant-ph↗

arXiv2020

Einstein-Podolsky-Rosen Paradox with Position-Momentum Entangled Macroscopic Twin Beams

Spatial entanglement is at the heart of quantum enhanced imaging applications and high-dimensional quantum information protocols. In particular, for imaging and sensing applications, quantum states with a macroscopic number of photons are needed to provide a real advantage over the classical state-of-the-art. We demonstrate the Einstein-Podolsky-Rosen (EPR) paradox in its original position and momentum form with bright twin beams of light by showing the presence of EPR spatial (position-momentum) entanglement. An electron-multiplying charge-coupled-device camera is used to record images of the bright twin beams in the near and far field regimes to achieve an apparent violation of the uncertainty principle by more than an order of magnitude. We further show that the presence of quantum correlations in the spatial and temporal degrees of freedom leads to spatial squeezing between the spatial fluctuations of the bright twin beams in both the near and far fields. This provides another verification of the spatial entanglement and points to the presence of hyperentanglement in the bright twin beams.

quant-ph↗

arXiv2019

Spatial squeezing in bright twin beams generated with four-wave mixing: constraints on characterization with an EMCCD camera

The observation of spatial quantum noise reduction, or spatial squeezing, with a large number of photons can lead to a significant advantage in quantum imaging and quantum metrology due to the scaling of the signal-to-noise ratio with the number of photons. Here we present a systematic study of the limiting factors that play a role on the measurement of spatial squeezing with an electron-multiplying charge coupled device (EMCCD) camera in the limit of bright quantum states of light generated with a four-wave mixing process in an atomic vapor cell. We detect a total number of photons per beam of the order 10$^8$ in 1 $μ$s pulses, which corresponds to a photon flux per beam of the order of 10$^{14}$ photons per second. We then investigate the role of different parameters, such as cell temperature, pump power, laser detunings, scattered pump background noise, and timing sequences for the image acquisition with the EMCCD camera, on the level of spatial squeezing. We identify critical parameters to obtain an optimum squeezing level and demonstrate that for bright beams it is essential to acquire images at a rate fast enough to overcome the effect of classical technical noise.

quant-ph↗