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Conference 12993
Quantum Technologies 2024
8 - 10 April 2024 | Londres 1/Salon 8, Niveau/Level 0
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Hot Topics I
8 April 2024 • 09:00 - 11:00 CEST | Auditorium Schweitzer, Niveau/Level 0
Session Moderators:
Paul Montgomery, Univ. of Strasbourg (France)
2024 Symposium Chair
9:10 hrs: City of Strasbourg Welcome
9:15 hrs: Speaker Introduction
Paul Montgomery, Univ. of Strasbourg (France)
2024 Symposium Chair
9:00 hrs: Welcome and Opening Remarks
9:10 hrs: City of Strasbourg Welcome
9:15 hrs: Speaker Introduction
12993-500
Photonic quantum technologies: from unravelling quantum foundations to advancing quantum integration and developing applications in quantum networks and computing
(Plenary Presentation)
8 April 2024 • 09:20 - 10:05 CEST | Auditorium Schweitzer, Niveau/Level 0
Show Abstract +
I will explore various facets of photonic quantum systems and their application in photonic quantum technologies. Firstly, I will focus into quantum foundations and by discuss quantum interference, a key element in photonic quantum technologies. I will highlight how the distinguishability and mixedness of quantum states influence the interference of multiple single photons – and demonstrate novel schemes for generating multipartite entangled quantum states. I will then address photonic quantum computing, specifically focusing on the building blocks of photonic quantum computers. This includes the generation of resource states essential for photonic quantum computing. I will then shift to photonic quantum networks, covering both their hardware aspects and showcasing quantum-network applications that extend beyond bi-partite quantum communication. Lastly, I will outline how photonic integration facilitates the scalability of these systems and discuss the associated challenges.
13013-501
Organic photonics for biomedical research and next generation displays
(Plenary Presentation)
8 April 2024 • 10:10 - 10:55 CEST | Auditorium Schweitzer, Niveau/Level 0
Show Abstract +
Joining the rich photophysics of organic light-emitting materials with the exquisite sensitivity of optical resonances to geometry and refractive index enables a plethora of devices with unusual and exciting properties. Examples from my team include biointegrated microlasers for real time sensing of cellular activity and long-term cell tracking, as well as the development of photonic implants with extreme form factors and wireless power supply that support thousands of individually addressable organic LEDs and thus allow optogenetic targeting of neurons deep in the brain with unprecedented spatial control. Very recently, by driving the interaction between excited states in organic materials and resonances in thin optical cavities into the strong coupling regime, we unlocked new tuning parameters which may play a crucial role in the next generation of TVs and computer displays to achieve even more saturated colour while retaining angle-independent emission characteristics.
Break
Coffee Break 11:00 - 11:30
Session 1:
Novel Platforms I
8 April 2024 • 11:30 - 12:40 CEST | Londres 1/Salon 8, Niveau/Level 0
Session Chair:
Tom Bienaimé, Univ. de Strasbourg (France)
12993-1
Cold Rydberg atom excitation mediated via an optical nanofiber
(Invited Paper)
8 April 2024 • 11:30 - 12:00 CEST | Londres 1/Salon 8, Niveau/Level 0
Show Abstract +
Complete control of light-matter interactions at a single quantum level is critical for quantum science applications such as precision measurements and information processing. Nanophotonic devices, developed with recent advancements in nanofabrication techniques, can be used to tailor the interactions between single photons and atoms. One example of such a device is the optical nanofibre, which provides an excellent platform due to the strongly confined transverse light fields, long interaction length, low loss, and diverse optical modes. This facilitates a strong interaction between atoms and guided light, revealing chiral atom-light processes and the prospect of waveguide quantum electrodynamics. This work highlights recent advances on optical nanofiber mediated excitation of cold rubidium Rydberg atoms for the creation of a 1D Rydberg array.
12993-2
8 April 2024 • 12:00 - 12:20 CEST | Londres 1/Salon 8, Niveau/Level 0
Show Abstract +
Scalable graph states play a crucial role in measurement-based quantum computation and various applications in quantum technologies that rely on entanglement. Generating these multipartite entangled states necessitates a quantum device that is both controllable and efficient, requiring a carefully designed generation protocol. In this study, we propose a method to prepare high-fidelity and scalable graph states in one and two dimensions. These states can be crafted within an atom-nanophotonic cavity using a state carving technique. Our systematic protocol involves carving out unwanted state components, facilitating the generation of scalable graph states through the adiabatic transport of a specific number of atoms confined in optical tweezers. We present an analysis of state fidelity and demonstrate that the probability of state preparation can be optimized by employing multiqubit state carvings and sequential single-photon probes. The results underscore the capability of an atom-nanophotonic interface to create graph states, paving the way for novel applications tailored to specific problems using scalable high-dimensional graph states with stationary qubits.
12993-3
8 April 2024 • 12:20 - 12:40 CEST | Londres 1/Salon 8, Niveau/Level 0
Show Abstract +
Silicon color centers have emerged as promising candidates for quantum information technologies, yet their interaction with electric fields is not well understood. We will discuss electrical manipulation of G-centers in silicon -- quantum emitters that photoluminesce in the telecom O-band. We fabricated lateral electrical diodes with an integrated ensemble of G centers in a commercial silicon on insulator wafer. Under application of a reverse-biased DC electric field, the ensemble of G-centers redshifts by approximately 1.4 GHz/V above a threshold “turn-on voltage.” The fluorescence intensity is modulated by increasing electric field, ultimately achieving 100% extinction. Finally, we use G center fluorescence to directly image the electric field distribution within the devices, obtaining insight into the spatial and voltage-dependent variation of the junction depletion region and the associated mediating effects on the ensemble. The emitter-field coupling is correlated to the photocurrent generated in the device. Our device architecture uniquely enables simultaneous optical and electrical manipulation of quantum emitters, and it is readily extensible to other quantum emitters.
Break
Lunch Break 12:40 - 14:00
Session 2:
Quantum Sensing and Metrology
8 April 2024 • 14:00 - 15:30 CEST | Londres 1/Salon 8, Niveau/Level 0
Session Chair:
Florent Baboux, Lab. Matériaux et Phénomènes Quantiques (France)
12993-4
Quantitative phase imaging enhanced by quantum correlation in a non-interferometric scheme
(Invited Paper)
8 April 2024 • 14:00 - 14:30 CEST | Londres 1/Salon 8, Niveau/Level 0
Show Abstract +
In this work we exploit entangled twin-beam to enhance quantitative phase retrieval of an object in a non-interferometric setting, only measuring the propagated intensity pattern after interaction with the object. The scheme achieves full field phase reconstruction with quasi-single-shot acquisition, not requiring time consuming raster-scanning of the sample. In our experiment a 40% improved precision has been achieved with respect to the corresponding classical scheme.
12993-5
8 April 2024 • 14:30 - 14:50 CEST | Londres 1/Salon 8, Niveau/Level 0
Show Abstract +
We present a novel quantum interferometer that contains two nondegenerated PDC crystals positioned in parallel and injection seeded by a narrow-linewidth coherent field at each idler modes. We show also that PDC crystals act as two quantum light sources that emit an entangled superposition state of a single signal photon associated with its conjugate idler which-source detectors. we use the same QI to evaluate the nonclassicality of signal photons inside our QI with the fidelity of the conjugated idler quantum states, i.e., single-photon added coherent states. We find that in fact the nonclassical measure $N$ is equal to the fidelity $F$ of the which-source detector states (idler quantum states), and the fringe visibility is given by the simple relation of $V = V_0 N$. Our QI operates, in principle, with a single-photon state well below the nonclassical regime of $ 0 \le N < 1$, where indistinguishability of which-source information where the single-photon comes from the PDC crystal results in the induced single-photon quantum coherence. Our finding may resolve the long-standing debate about the induced coherence without induced emission in the Zou-Wang-Mandel interferometer.
12993-6
8 April 2024 • 14:50 - 15:10 CEST | Londres 1/Salon 8, Niveau/Level 0
Show Abstract +
In quantum mechanics, the precision achieved in parameter estimation using a quantum state as a probe is determined by the measurement strategy employed. The quantum precision limit, a fundamental boundary, is defined by the intrinsic characteristics of the state and its dynamics. Theoretical results have revealed that in interference measurements with two possible outcomes, like the Hong Ou-Mandel interference, this limit can be reached under ideal conditions of perfect visibility and zero losses. However, in practice, this cannot be achieved, so precision never reaches the quantum limit. But how do experimental setups approach precision limits under realistic circumstances?
In this work, we provide a general model for precision limits in two-photon Hong-Ou-Mandel interferometry for non-perfect visibility and validate it experimentally using different quantum states. A remarkable ratio of 0.97 between the experimental precision and the quantum limit is observed, establishing a new benchmark in the field.
12993-7
8 April 2024 • 15:10 - 15:30 CEST | Londres 1/Salon 8, Niveau/Level 0
Show Abstract +
General relativity and quantum mechanics are the two frameworks through which we understand Nature. To date, they have remained valid to great extent in their respective domains. Regardless of the myriad of attempts to find a unified theory that can describe all of observable phenomena, the quest for unification continues.
One avenue for investigating the overlap of general relativity and quantum mechanics that is less ambitious but can still provide potentially observable and measurable predictions is that of quantum field theory in curved spacetime viewed through the lens of quantum information. In recent years, a great deal of attention has been given to this approach, which has provided novel and intriguing insights into phenomena that can be tested in the laboratory.
We present an investigation in the quantum nature of the gravitational redshift, seeking to understand which are the expected quantum dynamics that lead to the effective classical observable effect. We discuss the classical regime and show that more intriguing aspects are expected. We conclude discussing potential for detection in space-based experiments.
Break
Coffee Break 15:30 - 16:00
Session 3:
Integrated Devices
8 April 2024 • 16:00 - 17:30 CEST | Londres 1/Salon 8, Niveau/Level 0
Session Chair:
Martin Bowen, Institut de Physique et de Chimie des Matériaux de Strasbourg (France)
12993-8
8 April 2024 • 16:00 - 16:30 CEST | Londres 1/Salon 8, Niveau/Level 0
Show Abstract +
This research explores the integration of graphene as an on-chip shunt resistor in superconducting detectors, specifically superconducting nanowire single-photon detectors (SNSPDs). While SNSPDs offer advantages over traditional photodetectors, they face limitations related to latching and reset dead time. The study involves the development of hybrid detectors using NbTiN and graphene, marking the first application of a 2D material in this role. The fabrication employs lithography and chemical vapor deposition (CVD) processes. Experimental results show improved critical temperature, a broader superconducting transition, and reduced electrical hysteresis in the hybrid system. Under pulsed laser illumination, the non-latching behavior of NbTiN meanders with graphene demonstrates the efficacy of graphene as a shunt resistor, enhancing detector speed and detection efficiency. The study contributes valuable insights into the interaction between 2D materials and superconducting detectors, laying the groundwork for future advancements in this field.
12993-9
8 April 2024 • 16:30 - 16:50 CEST | Londres 1/Salon 8, Niveau/Level 0
Show Abstract +
Data protection and confidentiality have become a serious concern in today’s world. Their security is guaran-
teed by cryptographic protocols, which heavily rely on random numbers as a measure against predictability.
Classically, randomness is generated via complex but deterministic algorithms, which are vulnerable to attacks.
Quantum random number generators (QRNGs) have emerged as a promising solution, as they provide true
random numbers based on the intrinsic non-deterministic nature of quantum mechanics. However, critical chal-
lenges for QRNGs are the certification and quantification of their genuine randomness, especially in the presence
of untrusted devices, and their compactness for systematic deployment. In this feasibility study, to face these
challenges, we propose to use a silicon-photonic platform, leveraging on the concept of quantum contextuality
for a semi-device independent generator. In particular, we use Klyachko-Can-Binicioglu-Shumovsky (KCBS) in-
equality to assess a fundamental property of quantum measurements: that their outcomes depend on the specific
measurement context
12993-10
8 April 2024 • 16:50 - 17:10 CEST | Londres 1/Salon 8, Niveau/Level 0
Show Abstract +
Hybrid photonic devices, harnessing the advantages of multiple materials while mitigating their respective weaknesses, represent a promising solution to the effective on-chip integration of generation and manipulation of non-classical states of light encoding quantum information. We demonstrate a hybrid III-V/Silicon quantum photonic device combining the strong second-order nonlinearity and compliance with electrical pumping of the III-V semiconductor platform with the high maturity and CMOS compatibility of the silicon photonic platform. Our device embeds the spontaneous parametric down-conversion (SPDC) of photon pairs into an AlGaAs source and their subsequent routing to a silicon-on-insulator circuitry. This enables the on-chip generation of broadband telecom photon pairs by type 0 and type 2 SPDC from the hybrid device, at room temperature and with strong rejection of the pump beam. Two-photon interference with 92% visibility proves the high energy-time entanglement quality characterizing the produced quantum state, thereby enabling a wide range of quantum information applications.
12993-11
8 April 2024 • 17:10 - 17:30 CEST | Londres 1/Salon 8, Niveau/Level 0
Show Abstract +
Entangled photon-pairs are crucial for applications like quantum key distribution, sensing and imaging. For prospective use in real world devices, the challenge for entangled photon-pair sources (EPS) is to simultaneously meet high requirements regarding state fidelity, tunability etc. while maintaining a small foot print and high robustness. In this work, we develop an EPS that meets these demands. Using a sub-micron thick transition metal dichalcogenide (TMD) crystal, we show tunable generation of polarization entangled Bell states via spontaneous parametric down-conversion (SPDC). To the best of our knowledge, this is the first realization of SPDC in a TMD. In particular, we employ the TMD 3R-phase molybdenum disulfide (3R-MoS2), which due to its crystal symmetry intrinsically creates entanglement without needing external optical components. We experimentally demonstrate tuning between different maximally entangled states with constant generation efficiency and show pathways towards highly efficient and tunable TMD-based EPS using quasi-phasematching or cavity integration.
Session 4:
Quantum Communication
9 April 2024 • 09:00 - 10:30 CEST | Londres 1/Salon 8, Niveau/Level 0
Session Chair:
Síle Nic Chormaic, Okinawa Institute of Science and Technology Graduate Univ. (Japan)
12993-12
Enhancing free space DI QKD via employing NPA hierarchy method
(Invited Paper)
9 April 2024 • 09:00 - 09:30 CEST | Londres 1/Salon 8, Niveau/Level 0
Show Abstract +
Recently, there has been a growing focus on quantum communication due to its inherent security advantages. However, there are still many challenges that need to be addressed, such as the distribution of entangled states over long distances, closing the Bell test loopholes, and increasing the key rate. In this work, we present an innovative device-independent quantum key distribution (DI-QKD) protocol based on the distribution of near-maximally entangled multiphoton states across long distances. Our proposed strategy employs the resources available within the current landscape of integrated quantum photonic technology, including the utilization of squeezed vacuum states and photon-number-resolving detectors. Besides, this protocol enables entanglement sharing and quantum communication in free space.
12993-13
9 April 2024 • 09:30 - 09:50 CEST | Londres 1/Salon 8, Niveau/Level 0
Show Abstract +
In this work, we implement a proof-of-concept underwater free-space quantum key distribution (QKD) system and analyze its performance in a controlled laboratory test environment.
We implement a BB84 protocol with time-bin encoding operating at 520 nm. The quantum channel was composed of a five-meter-long tank equipped with the possibility of actively controlling the water turbulence.
Finally, we measure the quantum bit error rate (QBER) in the various scenarios and we report the results together with those relating to the parameters of the considered channel.
12993-14
9 April 2024 • 09:50 - 10:10 CEST | Londres 1/Salon 8, Niveau/Level 0
Show Abstract +
Quantum key distribution (QKD) is a technology that allows sharing secret cryptographic keys between two distant users (Alice and Bob), whose intrinsic security is guaranteed by fundamental principles of quantum mechanics.
QKD is a mature technology even if one of the main remaining challenges is the integration of different solutions in already deployed telecommunication fiber networks, in particular in long-haul segments. An approach able to cover long distances is the Twin-field QKD (TF-QKD) protocol; TF-QKD exploits interference of optical pulses in a central untrusted node (Charlie), allowing to double the communication distance with respect to the conventional prepare-and-measure solutions.
Here we present a solution to one of the main issues of Twin-Field QKD, the phase stabilization within the optical path, demonstrating a strong advantage in performances of real word TF- QKD and testing our solution in a segment of the Italian Quantum Backbone. Furthermore, we analyze in detail the expected gain in terms of key rate exploiting our stabilization technique in the main TF-QKD-based protocols, even when they are declared insensitive to the phase noise.
12993-15
9 April 2024 • 10:10 - 10:30 CEST | Londres 1/Salon 8, Niveau/Level 0
Show Abstract +
Photon loss is the fundamental issue toward the development of quantum networks. To circumvent loss quantum repeaters were proposed, which need high-performance quantum memories. We presented a new proposal that showed that co-moving satellite chains can enable untrusted quantum communication between any two points on Earth, using only reflection as an optical relay. In this process, diffraction loss is eliminated by using the curved satellite telescope mirrors to converge light. The satellite as a whole will effectively behave like a lens and contain beam divergence. The satellite chain is co-moving and hence tracking error is also eliminated within the chain. Effectively the chain of satellites would behave like a set of lenses in an optical table containing beam divergence and hence photon loss indefinitely. No high-performance new quantum hardware (like quantum memory or QND detectors) needs to be invented which was the principal bottleneck of the existing approaches based on quantum repeaters.
Break
Coffee Break 10:30 - 11:00
Session 5:
Novel Platforms II
9 April 2024 • 11:00 - 12:10 CEST | Londres 1/Salon 8, Niveau/Level 0
Session Chair:
Virginia D'Auria, Institut de Physique de Nice (France)
12993-16
Spintronics across individual atoms: an emerging quantum technology platform to encode information and harvest thermal energy
(Invited Paper)
9 April 2024 • 11:00 - 11:30 CEST | Londres 1/Salon 8, Niveau/Level 0
Show Abstract +
Despite its low-power and industrialization advantages, spintronics has so far not been featured among the many quantum technological platforms because embedding a quantum object with discrete electronic states within this class of solid-state device is challenging. I will present recent research into a quantum flavor of inorganic and molecular spintronics that utilizes the spin states of individual magnetic atoms to encode quantum information and autonomously harvest thermal energy within solid-state vertical pillar devices.
12993-17
9 April 2024 • 11:30 - 11:50 CEST | Londres 1/Salon 8, Niveau/Level 0
Show Abstract +
Single photon emission from quantum defects is characterized by performing the Hanbury-Brown Twiss (HBT) experiment to quantify the second-order autocorrelation (g(2)(t)) function. Photonic structures embedding quantum defects can have tunable emission parameters such as intensity, polarization, wavelength, etc. Here, we study single photon emission from a diamond nanopillar array containing nitrogen-vacancy (NV) centers. We observe the apparent dependence of antibunching on the angle of excitation and detection in such photonic structures. Our results highlight the role of structural factors in the g(2)(t) function and radiative lifetime of quantum defects in photonic structures.
12993-18
9 April 2024 • 11:50 - 12:10 CEST | Londres 1/Salon 8, Niveau/Level 0
Show Abstract +
Quantum emitters in two-dimensional layered hexagonal boron nitride are quickly emerging as a highly promising platform for next-generation quantum technologies. However, precise identification and control of defects are key parameters to achieve the next step in their development. We conducted a comprehensive study by analyzing over 10,000 photoluminescence emission lines, revealing 11 distinct defect families within the 1.6 to 2.2 eV energy range, challenging the hypotheses of a random energy distribution. These findings provide valuable insights to decipher the microscopic origin of emitters in hBN. The spectral spacing between defect families could serve as a key parameter for theoretical investigations We also explored the influence of hBN host morphology on defect family formation, demonstrating its crucial impact. By tuning flake size and arrangement we achieve selective control of defect types while maintaining high spatial density. This offers a scalable approach to defect emission control, diverging from costly engineering methods.
Break
Lunch/Exhibition Break 12:10 - 14:00
Session 6:
Quantum Imaging
9 April 2024 • 14:00 - 15:30 CEST | Londres 1/Salon 8, Niveau/Level 0
Session Chair:
Ivano Ruo Berchera, Istituto Nazionale di Ricerca Metrologica (Italy)
12993-19
taking photos of quantum entanglement
(Invited Paper)
9 April 2024 • 14:00 - 14:30 CEST | Londres 1/Salon 8, Niveau/Level 0
Show Abstract +
Entanglement is a central resource in quantum technologies. In this respect, high-dimensional entangled states are very promising for developing robust quantum communication schemes and enhanced imaging protocols. Being able to quantify high-dimensional entanglement quickly and accurately is therefore essential. However, to date, all experimental methods use assumptions about the detected state or imperfect measurement techniques, such as single-outcomes and accidental subtractions. Entanglement certification processes are therefore not only slow, but they also contain loopholes, which is not acceptable in adversarial scenarios such
as quantum key distribution (QKD). In our work, we demonstrate the certification of high-dimensional entanglement using an event-based single-photon sensitive camera by performing measurements in two mutually unbiased bases. Our work provides an experimental method allowing for the efficient characterization of high-dimensional quantum states, paving the way for the development of high-dimensional QKD protocols and practical photon-pairs-based quantum imaging approaches.
12993-20
9 April 2024 • 14:30 - 14:50 CEST | Londres 1/Salon 8, Niveau/Level 0
Show Abstract +
Quantum illumination uses correlations between pairs of modes (signal and idler) to improve confidence in object detection in the presence of a much brighter background photon noise . A common practical approach is to use threshold detectors to measure the idler mode, as is done in quantum lidar schemes. We investigate optimising such schemes to improve target detection confidence and find the surprising results that making signal detection efficiency worse is sometimes better, that we should use weaker pulses that are more closely spaced and that we should not postselect on the idler detector firing.
12993-21
9 April 2024 • 14:50 - 15:10 CEST | Londres 1/Salon 8, Niveau/Level 0
Show Abstract +
This study falls within the field of quantum imaging. Photon-pair correlations in spontaneous parametric down conversion processes are ubiquitous in quantum photonics and its applications. In this work, researchers structure these correlations in the form of images of arbitrarily chosen objects. They show that their approach works with both amplitude and phase objects, even when the beam intensity is also spatially shaped. Furthermore, they demonstrate that - in certain cases - the transmission of quantum correlations-encoded images through scattering media is more efficient than using classical light. Their approach enables the transmission of complex, high-dimensional information using in quantum correlations of photons, which can be useful for developing quantum communication and imaging protocols.
12993-22
9 April 2024 • 15:10 - 15:30 CEST | Londres 1/Salon 8, Niveau/Level 0
Show Abstract +
We study the feasibility of polarization-entangled photon pairs to be applied for probing the density of living microorganisms in a microfluidic chamber. We investigate the polarization response of scattering samples via quantum state change and relate this to different density levels of microorganisms on example of yeast cells in water solution.
Break
Coffee Break 15:30 - 16:30
Hot Topics II
9 April 2024 • 16:30 - 18:05 CEST | Auditorium Schweitzer, Niveau/Level 0
Session Moderator:
Anna Mignani, Istituto di Fisica Applicata "Nello Carrara" (Italy)
2024 Symposium Chair
Welcome and Opening Remarks
Speaker Introduction
Anna Mignani, Istituto di Fisica Applicata "Nello Carrara" (Italy)
2024 Symposium Chair
16:30 hrs
Welcome and Opening Remarks
Speaker Introduction
13004-500
Nonlinearities, timescales and optical cavities: a toolbox for photonic reservoir computing
(Plenary Presentation)
9 April 2024 • 16:35 - 17:20 CEST | Auditorium Schweitzer, Niveau/Level 0
Show Abstract +
Optical cavities with nonlinear elements and delayed self-coupling are widely explored candidates for photonic reservoir computing (RC). For time series prediction applications that appear in many real-world problems, energy efficiency, robustness and performance are key indicators. With this contribution I want to clarify the role of internal dynamic coupling and timescales on the performance of a photonic RC system and discuss routes for optimization.
By numerically comparing various delay-based RC systems e.g., quantum-dot lasers, spin-VCSEL (vertically emitting semiconductor lasers), and semiconductor amplifiers regarding their performance on different time series prediction tasks, to messages are emphasized: First, a concise understanding of the nonlinear dynamic response (bifurcation structure) of the chosen dynamical system is necessary in order to use its full potential for RC and prevent operation with unsuitable parameters. Second, the input scheme (optical injection, current modulation etc.) crucially changes the outcome as it changes the direction of the perturbation and therewith the nonlinearity. The input can be further utilized to externally add a memory timescale that is needed for the chosen task and thus offers an easy tunability of RC systems.
13012-500
General-purpose programmable integrated photonics processors: what things can you do with them?
(Plenary Presentation)
9 April 2024 • 17:20 - 18:05 CEST | Auditorium Schweitzer, Niveau/Level 0
Show Abstract +
Programmable photonic circuits manipulate the flow of light on a chip by electrically controlling a set of tunable analog gates connected by optical waveguides. Light is distributed and spatially rerouted to implement various linear functions by interfering signals along different paths. A general-purpose photonic processor can be built by integrating this flexible hardware in a technology stack comprising an electronic monitoring and controlling layer and a software layer for resource control and programming. This processor can leverage the unique properties of photonics in terms of ultra-high bandwidth, high-speed operation, and low power consumption while operating in a complementary and synergistic way with electronic processors. This talk will review the recent advances in the field and it will also delve into the potential application fields for this technology including, communications, 6G systems, interconnections, switching for data centers and computing.
Posters-Tuesday
9 April 2024 • 18:10 - 20:00 CEST | Galerie Schweitezer, Niveau/Level 0
Conference attendees are invited to attend the Photonics Europe poster session on Tuesday evening. Come view the posters, enjoy light refreshments, ask questions, and network with colleagues in your field. Authors of poster papers will be present to answer questions concerning their papers. Attendees are required to wear their conference registration badges to the poster sessions.
Poster Setup: Tuesday 10:00 - 17:30 hrs
Poster authors, view poster presentation guidelines and set-up instructions at http://spie.org/EPE/poster-presentation-guidelines.
Poster Setup: Tuesday 10:00 - 17:30 hrs
Poster authors, view poster presentation guidelines and set-up instructions at http://spie.org/EPE/poster-presentation-guidelines.
12993-31
On demand | Presented live 9 April 2024
Show Abstract +
This study provides insights into the current limitations of quantum machine learning compared to classical machine learning and identifies areas for future research. We present a novel approach that utilizes real IBM quantum computers to classify celestial objects within the extensive Sloan Digital Sky Survey Data Release 18 (SDSS-V DR18) dataset. Despite persistent challenges in both hardware and software, quantum computers are being explored as tools for enhancing machine learning performance in comparison to classical methods due to potential upside. This investigation delves into the untapped potential of quantum machine learning and quantum neural networks in tackling the complexities of processing vast telescope data. By leveraging quantum technologies, we aim to expedite the analysis of large complex data, unveiling hidden patterns, and propelling specialized fields such as astronomical research into the quantum era.
12993-32
9 April 2024 • 18:10 - 20:00 CEST | Galerie Schweitezer, Niveau/Level 0
Show Abstract +
We discuss the observed delayed-choice quantum erasers using a laser for both single photon and continuous wave versions. Due to the self-interference of a single photon in an interferometer, the same results observed in a cw regime are not weird but rather straightforward. These seemingly contradictory observations of the quantum eraser in a classical version are explained by selective measurements of the original detection events using a rotated polarizer. For this, pure coherence analysis is applied to the experimental quantum-eraser scheme, where the violation of the cause-effect relation is not for individual single photons but for an ensemble of them in terms of information. Thus, the weird quantum feature of the quantum erasers is now clearly understood in a deterministic way via a modified measurement scheme of coherence photons.
12993-33
On demand | Presented live 9 April 2024
Show Abstract +
Spontaneous-Parametric-Down-Conversion-produced photons, which are positively correlated in frequency, possess properties favourable in the context of Fourier-domain Quantum Optical Coherence Tomography (Q-OCT). These include the ease of generation and a high number of anti-diagonals needed for efficient artefact removal. On the other hand, a small diagonal width leads to a reduced axial resolution of the resultant images. The spectral characteristics of such light is analysed both theoretically and experimentally and its validity for Q-OCT imaging discussed.
12993-34
On demand | Presented live 9 April 2024
Show Abstract +
Continuous Variable Quantum Key Distribution (CV-QKD) uses quadrature amplitude modulation to encode bits of information on weak coherent states. We experimentally demonstrate discretely modulated CV-QKD across a 150 m long free-space optical (FSO) link over the two buildings with a four symbol constellation. QPSK symbols generated at 100 MHz from a Zynq Ultrascale+ Board were fed to an I/Q transmitter and thence onto a 1550nm laser. A 90 degree hybrid coherent receiver, with a 1 GHz bandwidth, was used to detect both quadratures. Post-processing with a k- means clustering allowed us to recover the bit values with a BER of approximately around 25 - 35%. Our experiments focus on understanding the change in BER in the presence of varying levels of attenuation over the FSO channel.
12993-35
On demand | Presented live 9 April 2024
Show Abstract +
In this work, we focus on optimizing waveguides based on lithium niobate on insulator (LNOI) for the generation of cross-polarized spectrally pure photons at telecommunication wavelength using type II spontaneous parametric down-conversion (SPDC) process. Our optimization process is based on avoiding lateral leakage losses for all the modes involved in considered SPDC process by choosing waveguide parameters appropriately. In addition, we also ensure single mode operation for all the interacting wavelengths. We further engineer the waveguide such that it satisfies group index matching for generating spectrally pure single photons with high purity (>95 %). Such single-mode and loss-free waveguides are poised to have broad applications in both classical and quantum optical fields.
12993-36
On demand | Presented live 9 April 2024
Show Abstract +
Optical quantum technologies, especially quantum communication, yield higher potential with a network of many
integrated quantum systems. Compatibility among each component is then essential. A single quantum system
that can be used for different building blocks is ideal, as it automatically ensures a highly efficient interface
between the different components. Fluorescent defects in two-dimensional hexagonal boron nitride (hBN) have
been demonstrated to be a promising candidate to fulfil this requirement. This work herein demonstrates the
potential of hBN defects for being both quantum emitter and quantum memory. The emission wavelengths
of a large number of defects have been characterized. Together with thorough photophysical properties, these
defects can be directly compared with experiments. The performance of hBN quantum memory has also been
evaluated and provided with an experimental condition to achieve 95% efficiency. For an efficient global quantum
network, the rigorous comparison of compatibility between hBN defects and other quantum components has
been investigated. This work, therefore, serves as a recipe for generating a universal solid-state quantum system.
12993-37
On demand | Presented live 9 April 2024
Show Abstract +
We present our first results concerning a compact dual cold atom accelerometer-gyroscope, which is incorporated within the framework of the development of a cold atom inertial measurement unit. The sensor is sensitive to rotations if the atoms enter the interferometer with an initial velocity. We therefore propose a scheme compatible with a compact multi-axis sensor in which the atoms are horizontally launched thanks to a magnetic gradient and interrogated with a single Raman laser. In this work, the quantum sensor has been hybridized with a conventional accelerometer and gyroscope, which has resulted in respectively 100-fold and 5-fold bias stability improvements compared to the conventional sensors alone. Dynamic rotation rate measurements have also been performed and demonstrated a 1% agreement between the two sensors. This work provides a pathway towards autonomous navigation using cold-atom sensors.
12993-38
On demand | Presented live 9 April 2024
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This study explores the versatile framework of time-frequency variables in the context of quantum information, with a specific focus on the use of single photons as a paradigmatic system. In our first analysis, we discern the contributions of intensity and spectral resources, unveiling their impacts on the precision of parameter estimation as the number of probes increases. Remarkably, we demonstrate the potential for quadratic scaling using quantum mode correlations and derive mathematical expressions for the optimal states.
In a second investigation, inspired by the state achieving the Heisenberg limit, we introduce a novel method for encoding GKP (Gottesman, Kitaev, and Preskill) states in our paradigmatic system. We analyze the scalability of error detection and correction with the total photon number. We demonstrate that these codes can effectively correct displacements in time-frequency phase space and photon losses. This research highlights the unifying potential of time-frequency variables as a platform for diverse quantum applications.
12993-39
9 April 2024 • 18:10 - 20:00 CEST | Galerie Schweitezer, Niveau/Level 0
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Intrinsic parasitic heating in silicon-based optomechanical devices remains a bottleneck which greatly limits the experimental efficiency and quantum correlations that can be achieved with such devices. Here, we design and fabricate quasi-2D optomechanical crystal cavities (OMCs) and characterize their properties, to minimize said heating effect. Our OMC design is optimized with respect to the anisotropy of the silicon stiffness tensor enabling long mechanical lifetimes exceeding milliseconds. We experimentally demonstrate reduced residual thermal population in the mechanical mode of interest as well as stronger quantum correlations between single phonon creation and readout compared to 1D nanobeam OMCs at the same optomechanical scattering probability. The improved thermal performance of such quasi-2D structures opens up possibilities for novel experiments in quantum optomechanics such as optomechanical state reconstruction or fast resetting of a mechanical quantum memory.
12993-40
On demand | Presented live 9 April 2024
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AlGaAs Bragg-reflection waveguides offer the potential for on-chip entangled photon sources which integrate the entangled photon source and the pump source in the same chip. We designed and experimentally realized an AlGaAs Bragg-reflection waveguide structure in which the effective refractive indices for TE and TM polarized photons are the same to improve the degree of entanglement without external compensation. This was realized by appropriate choice of the ridge width of 1.8 µm, which offers lateral optical confinement. The difference in effective refractive indices has been reduced by more than a factor of 10 compared to waveguides of several micron width. The influence of waveguide width and length on single and coincidence rates, coincidence accidence ratio and the degree of entanglement will be discussed.
12993-41
On demand | Presented live 9 April 2024
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Polarization-entangled photon sources (EPS) are an important enabling technology in the fields of quantum sensing, quantum communication, and quantum computing. Recently, a need has arisen for efficient sources of entangled photons with high brightness and phase stability, for use in free space and fiber-based quantum communication links. In this work, we present a prototype of EPS based on commercial bulk opto-mechanical components, generating photon pairs via type-0 parametric down-conversion (SPDC). The source is configured in a linear interferometer, where a dual beam displacement is performed by symmetrically disposed birefringent components. The pairs emission can be prepared as an N00N state for quantum sensing, or as a Bell state for entanglement-based quantum key distribution (QKD) protocols. We show a maximal Bell inequality violation, on >99% average visibility, proving the high quality of the generated entanglement. The unique geometry of this interferometer is intrinsically symmetric, thus completely removing any temporal walk-off and decoherence between the two components of the Bell state, and enhancing its suitability for various on-field quantum applications.
12993-42
On demand | Presented live 9 April 2024
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“Schrödinger cat states” (SCS), which are coherent superpositions of two dephased coherent states, have been proven to be valuable resources for quantum computing, quantum communication, and quantum metrology. In this work, we present an experimental implementation of a SCS source using an iterative scheme. We use a heralded photon source based on parametric down conversion and a quantum memory cavity. The latter consists of a low losses cavity comprising a fast Pockels cell and a polarizing beam splitter (PBS), allowing us to store a first single photon, waiting for a second one to be generated. We then entangle the stored photon and the incoming photon using the PBS and the Pockels cell to perform polarization manipulation. A homodyne detection then performs a quadrature measurement on one part of the entangled state. This is conditioning measurement: if the result is “X=0”, then the other part of the state is projected on a SCS. A first version of the experiment allowed us to generate SCS at a rate of 100 Hz with a fidelity of 47% after a 184ns long storage.
12993-43
On demand | Presented live 9 April 2024
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This study falls within the emerging field of quantum optics in scattering media. By employing wavefront shaping, researchers successfully transmitted spatially entangled photon pairs through scattering media, mitigating optical disturbances by wavefront shaping. They maintained entanglement with a dimensionality of 17 after propagation, opening avenues for applications in quantum microscopy and quantum communication. Interestingly, this work also shows that in certain cases ,quantum entanglement can be transmitted through a complex medium, while classical light remains scattered
12993-44
On demand | Presented live 9 April 2024
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Bell tests serve as a fundamental tool in both quantum technologies and quantum foundations investigation. The traditional Bell test framework involves the use of projective measurements, which, because of the wavefunction collapse and the Heisenberg uncertainty principle, do not allow for the full estimation of the Bell parameter from each entangled pair.
In this work, we propose a novel weak-measurement-based scheme enabling the complete estimation of the entire Bell parameter from each entangled pair. Moreover, this approach prevents the collapse of the quantum state wavefunction, thereby preserving the entanglement within it. Our results, showing a 6 standard deviations violation of the Bell inequality tested, are obtained while leaving the entanglement within the photon pair almost unaltered after the weak measurement scheme (as demonstrated by our quantum tomographic reconstructions), allowing to exploit it for further foundational or practical purposes.
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The quantum technology unit of the Leonardo Labs has designed an imaging system that can be employed in Non-Line-Of-Sight scenarios where an obstacle is in between the target and the imager. In this scenario, laser pulses are used to scan surfaces that scatter and diffuse the light into the concealed areas, then the photons that interact with the target and are back-reflected to the imager are detected. The hidden area is finally retrieved with a sophisticated computational algorithm that tackles the inverse problem, unveiling real-time images of hidden targets. An Artificial Intelligence approach further optimizes target profile reconstruction using correlation from high-resolution acquisitions, potentially transforming defense and security applications. Leonardo's quantum imaging technology has the power to reveal and track previously imperceptible targets, as evidenced by real-time non-line-of-sight imaging experiments.
12993-46
On demand | Presented live 9 April 2024
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We experimentally realized a chip-based source-independent QRNG. The source-independent scheme provides a solution for the balance between the practical and device-independent QRNGs, which closes the security loopholes from the source, and can be easily realized with respect to the device-independent scheme based on loophole-free Bell test. For the measurement part, the imperfections of the detector are modeled and the practical loopholes in receiver side are thus closed. For the producibility, we use the silicon-on-illustrator (SOI) platform to integrate the optical path and detectors on chip. In this way, except for the local oscillator source, all the devices required by our QRNG scheme are integrated on a chip, which significantly promotes the miniaturization and scaling capabilities. The final generation rate is 15.6 Gbps, and the final random numbers well pass all the test items of NIST statistical tests, which demonstrates the practicability of a QRNG with source loophole-free, complete practical receiver modeling and chip-based devices.
12993-47
9 April 2024 • 18:10 - 20:00 CEST | Galerie Schweitezer, Niveau/Level 0
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We present a robust approach for minimally-destructive measurement of the number of atoms of an ultracold atomic ensemble. The measurement technique relies on the Faraday paramagnetic effect: when off-resonant light passes through a polarized atomic cloud, undergoes optical rotation in proportion to the number of atoms. Since it relies on circular bi-refingence rather than absorption, this measurement method preserves quantum coherences and has a negligible impact on atomic temperature. It incorporates a balanced polarimetry scheme using photodiodes and time-dependent magnetic fields to deliver a simple and robust to external perturbation system. Its applications include quantum-enhanced measurements, the preparation of atomic states with adjustable atom numbers, and finds application in areas such as atomic clocks, inertial sensors, quantum computing, quantum simulations, and fundamental physics experiments like gravitational detectors.
12993-48
9 April 2024 • 18:10 - 20:00 CEST | Galerie Schweitezer, Niveau/Level 0
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Recent years have shown significant advances in the field of chip-scale atomic-vapor based quantum sensors. Here, we present our recent explorations in remote quantum sensing utilizing mm-scale micromachined vapor cells tailored separately for two different types of sensing modalities: First, we performed remote magnetometry, measured an ambient magnetic field with a standoff distance of ~10 meters and a sensitivity of ~1 pT/√Hz in an unshielded environment. In the second study, we demonstrate remote Rydberg electrometry and detect the Autler-Townes splitting in Rydberg levels whilst subject to a RF fields of ~ 15 GHz.Our mm-scale cell dimension allows us to access the subwavelength regime (λ/10) of this RF-field. Owing to the wafer-scale fabrication process of micromachined-vapor cells, our presented sensors are highly scalable, and allow seamless integration of other flat-photonic-elements to facilitate efficient density control, and light-collection. As such, pave the way to a myriad of novel and diverse applications in atmospheric studies, ordnance detection, and microscopy.
12993-49
CANCELED: Single mode coupled emission of resonant cw excited GaAs quantum dots
9 April 2024 • 18:10 - 20:00 CEST | Galerie Schweitezer, Niveau/Level 0
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In order to provide quantum light of isolated systems properly usable for quantum applications, an efficient excitation and extensive collection is required. Single molecules and cavity confined quantum dots are convenient sources. The coupling to the excited state is maximized on resonance, but challenges the usability of the emitter due to the effort for separation of the optical excitation mode from the mode of emission. A temporal, spacial, spectral, or combined method for separation is typically used.
Here we present a realization of a single photon emitter under resonant excitation in a confocal setup coupled into a single mode fiber with the emission mode filtered by polarization.
For resonant cw excitation of GaAs semiconductor quantum dots a SNR of polarization suppression up to 400 and count rates of 2 Mcps are archived by using a collecting lens with NA 0.68 only. Further investigations regarding the blinking behavior are possible as well as probing alternative emitters like single molecules.
12993-50
On demand | Presented live 9 April 2024
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Integrated photonics is rapidly advancing, poised to revolutionize quantum information processing by scaling from a few qubits to encompassing tens of thousands. Quantum Photonic Integrated Circuits are pivotal in this evolution, leveraging classical Photonic Integrated Circuit principles. This transition necessitates precise design and modeling adhering to quantum information rules. To aid this shift, a Mathematica-based tool using the Quantum extension package has been developed. This software simulates output states of quantum photonic circuits comprising beam splitters and phase shifters. Input configurations in Fock states simulate single photons or coherent inputs, producing output probabilities for detecting photons at each port. The tool accommodates variable beam splitter ratios and phase shifters, validating its functionality by analyzing known photonic circuits. Ultimately, this software aims to facilitate testing and validation of simple photonic circuits in the quantum regime.
12993-51
On demand | Presented live 9 April 2024
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Our research focuses on utilizing optical switches to enhance the key rate of Decoy State BB84 Quantum key distribution (QKD) systems. This study aims to enhance the secure key rate via optical-switch-based polarization multiplexing. We have conducted a proof-of-concept experiment using Python productivity for Zynq (PYNQ), a coupler, and some Variable Optical Attenuators (VOA) to demonstrate precise polarization state switching in this work. Our experimental results clearly distinguish between different decoy states and polarization states. Our proposed enhancement holds significant potential since optical switch designs have been demonstrated to achieve attosecond switching speeds in the literature.
12993-52
9 April 2024 • 18:10 - 20:00 CEST | Galerie Schweitezer, Niveau/Level 0
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Adaptive optics (AO) has revolutionized imaging in many applications by enabling the correction of optical aberrations. However, in label-microscopes, conventional AO are limited by the absence of a guidestar, and the need to choose an image-based optimisation metric. Here, we propose an entanglement-enabled approach that exploits photon-pair correlations to directly access and correct the point-spread function of the imaging system. This method is independent of sample and imaging modality, and is guidestar-free. We demonstrate the concept in a brightfield configuration by imaging samples in the presences of aberrations operating with a source of spatially-entangled photon pairs. We show that our approach performs better than conventional AO in correcting certain types of aberrations, particularly in cases involving significant defocus. Our work improves AO for label-free microscopy, and could play a major role in the development of quantum microscopes, in which optical aberrations can counteract the advantages of using entangled photons and undermine their practical use.
12993-53
On demand | Presented live 9 April 2024
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In the simplest definition, a quantum battery is defined as a quantum system that can store energy. Recently, quantum battery has attracted a lot of interest due to its better performance than the classical one in terms of charging speed and stored energy. This superior performance comes from the quantum effects, such as quantum entanglement and correlations. The main problem to tackle in quantum battery is to achieve a quantum battery that stores more energy with faster charging time. In this work, we consider a model of quantum battery with nonlinearity effect: Kerr nonlinearity and quadratic driving. We show by adding nonlinearity to the system, the performance of the quantum battery in terms of stored energy and charging time becomes better. The Kerr nonlinearity induces an-harmonicity in the energy levels of the battery, from which we show that the charging time of the Kerr battery is faster than the case of harmonic oscillator battery, while the stored energy is larger than the case of qubit battery. On the other hand, quadratic driving leads to a squeezed quantum battery, which generates plentiful useful energy near to critical points.
12993-54
On demand | Presented live 9 April 2024
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We discuss the nonclassicality of output fields from seeded nondegenerate optical parametric oscillator (OPO), i.e., two-mode stabilized squeezed coherent state (SSCS) of light with controllable nonclassicality. Our method involves seeding phase-coherent bichromatic fields into a nondegenerate OPO, where the global phase difference between the bichromatic seed and pump fields plays a central role. we show that the two-mode SSCS has its nonclassical measure at its minimum possible value with an effective displacement that compensates for single-photon losses with injected photons. As a result, the SSCS has a larger mean photon number and controllable nonclassicality compared to an OPO without seed fields. We also show that a near-perfect squeezing level can be obtained at that effective displacement without being subject to injection rates. We believe that the proposed quantum source of two-mode SSCS with controllable nonclassicality would be useful for continuous-variable photonic quantum information processing.
12993-55
On demand | Presented live 9 April 2024
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The rubidium two-photon optical atomic clock is a promising technology offering a remarkable balance of compactness, stability and reliability. Its long-term stability, however, is often limited by the AC Stark effect to a few 10-14 above 1000 seconds integration time. Through this effect, instabilities of the 778 nm probe laser intensity translate into clock frequency instabilities. To address this issue, we mitigate the AC Stark shift with a supplementary 1556 nm laser beam derived from the same oscillator as the probe. This laser induces a frequency shift which counteracts the one caused by the probe beam. By optimizing the intensity ratio between these beams, we achieve a significant reduction in sensitivity of frequency to overall laser power changes, surpassing 10 dB reduction. This important step towards the goal of fractional frequency instabilities below 10-15 with a vapor-cell based clock paves the way for enhanced performance in compact atomic timekeeping technologies.
12993-57
On demand | Presented live 9 April 2024
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Magneto-optical properties of a diverse range of materials has been of great interest due to their wide applications in science and industry. While the properties of these materials are well investigated at the visible wavelength range, their behaviour at (IR) wavelengths is less explored, because of technical challenges in IR spectroscopy. Herein, we demonstrate an easily implementable, yet inexpensive method, that is based on quantum interference of correlated and non-degenerate photon pairs, for performing metrology of magneto-optical properties at IR wavelengths. Our method allows us performing spectral metrology of Verdet constant at different IR wavelengths via the detection of visible light.
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We present the quantum game called QTris, which in a concise set of rules describes the quantum mechanics of nine qubits through the conceptual setup of preparations, operations, and measurement.
We show that the winning game strategies do imply an interpretation of the quantum state and the difference between classical mixtures and coherent superpositions. This interpretation is clear-cut, free of metaphors, and we speculate free of paradoxes.
We show how QTris can be used to develop new quantum algorithms in the framework of quantum game theory.
We show how the game can be used as a self-contained course in quantum mechanics for both high-school and first year university students.
12993-59
On demand | Presented live 9 April 2024
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We report a quantum diamond microscope for rapid, spatially resolved magnetic imaging across a wide-field of view. We use it to measure optically detected magnetic resonance spectra of randomly oriented single crystal nanodiamonds with dense NV- ensembles, serving as local sensors of magnetic fields. A novel planar microwave resonator, able to produce arbitrary in-plane polarizations is used for polarization-sensitive control of electron spins. The resonator exhibits more than 200 MHz bandwidth, extended homogeneous region, and magnetic field strength surpassing 29 A/m at 1 W input power. Circularly polarized microwaves are used to identify selected spin-transitions in order to retrieve the direction of magnetic field. The presented system holds potential for applications in diverse fields, including material science, biology, and space research..
12993-60
On demand | Presented live 9 April 2024
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We use Si vacancy centers in a commercial power electronics chip made of 4H silicon carbide, a material widely used for power-electronics chips, for on-chip magnetometry. We employ optically detected magnetic resonance to determine the magnetic field strength and orientation angle by means of the spin transitions of the Si vacancies. We then use a differential evolution algorithm to robustly retrieve the magnetic field parameters from the optically detected magnetic resonance spectra irrespective of the magnetic field strength. The approach presented here shows promise in robust retrieval of magnetic field parameters, and can be applied to on-chip power device magnetometry.
Session 7:
Quantum Information and Sensing
10 April 2024 • 09:00 - 10:30 CEST | Londres 1/Salon 8, Niveau/Level 0
Session Chair:
Hugo Defienne, Institut des nanosciences de Paris (France)
12993-23
Quantum information and sensing with structured light
(Invited Paper)
10 April 2024 • 09:00 - 09:30 CEST | Londres 1/Salon 8, Niveau/Level 0
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Vectorial modes of light, a type of structured light where the polarization varies across the beam profile, are a useful tool both in classical and quantum applications. In quantum communication, for instance, these modes enable rotational invariant protocols, therefore overcoming the requirement of a shared reference frame between users. Moreover, structured light can be a resource for enhanced sensing purposes as for instance in the “photonic gears” technique. This quantum inspired scheme enables a boost of sensitivity in mechanical displacements measurement thanks to a bidirectional mapping between the polarization state and a properly tailored vectorial mode of a paraxial light beam. Finally, we will discuss how quantum interference can be controlled and tailored for structured light modes, therefore providing a key ingredient for exploiting the full potential of complex light in the quantum domain.
12993-24
10 April 2024 • 09:30 - 09:50 CEST | Londres 1/Salon 8, Niveau/Level 0
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The continuous nature of the frequency degree of freedom in a single photon allows for a high-dimensional encoding scheme, reducing optical costs. Discretizing the frequency allows for defining qubits that are robust against temporal and spectral broadening. Errors can occur during single photon manipulation and optical fiber propagation. Cross-talk between classical and quantum signals within optical fibers also affects these encodings. To address temporal and frequency broadening issues in these encodings, two methods are explored. One relies on costly non-linear optics, while the second solely utilizes linear optics. The second method involves a teleportation-based error correction protocol, where a noisy frequency qubit carrying quantum information becomes entangled with a less noisy frequency-entangled state. This process involves Bell measurements and inherently incorporates error correction, as the remaining frequency single-photon state, following the protocol, becomes associated with a lower-noise entangled state in both time and frequency domains (Applied Sciences 13, 9462).
12993-25
10 April 2024 • 09:50 - 10:10 CEST | Londres 1/Salon 8, Niveau/Level 0
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Fundamental phenomena like Quantum Zeno effect (QZE) and anti-Zeno effect (AZE) have been recognized as relevant tools for quantum control.
Along this line, here we present two experiments in which we demonstrate the capability to extract information on noise events by exploiting QZE and AZE.
In the first experiment, we realize noise diagnostics by frequent measurement, showing how a single photon undergoing a noise process (e.g., random polarization fluctuations) can diagnose non-Markovian temporal correlations within such a noise.
In the second one, instead, we show how, by protecting via QZE a photonic qubit in a noisy quantum channel, it is possible to estimate the statistical distribution of the microscopic noise (decoherence) events by using the qubit itself as a probe.
These techniques can become indispensable under extremely faint illumination, when traditional interferometric methods are usually ineffective.
12993-26
10 April 2024 • 10:10 - 10:30 CEST | Londres 1/Salon 8, Niveau/Level 0
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Programmable optical circuits form a key part of quantum technologies today. As the size of such circuits is increased, maintaining precise control over every individual component becomes challenging. Here we show how embedding an optical circuit in the higher-dimensional space of a large mode-mixer allows us to forgo control over individual elements while retaining a high degree of programmability over the circuit. Using this approach, we implement high-dimensional linear optical circuits within a commercial multi-mode fiber placed between controllable phase planes. We employ these circuits to manipulate high-dimensional entanglement in up to 7 dimensions, demonstrating their application as fully programmable quantum gates. Furthermore, we show how these circuits turn the multi-mode fiber itself into a generalized multi-outcome measurement device, allowing us to both transport and certify entanglement. Finally, we show how high circuit fidelity can be achieved with a low circuit depth by harnessing the resource of a high-dimensional mode-mixer. Our work serves as an alternative yet powerful approach for realizing precise control over high-dimensional quantum states of light.
Break
Coffee Break 10:30 - 11:00
Session 8:
Single-photon Emitters
10 April 2024 • 11:00 - 12:00 CEST | Londres 1/Salon 8, Niveau/Level 0
Session Chair:
Vincenzo D’Ambrosio, Univ. degli Studi di Napoli Federico II (Italy)
12993-27
10 April 2024 • 11:00 - 11:20 CEST | Londres 1/Salon 8, Niveau/Level 0
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We present a promising solid-state system able to emit triggered single-photons in the blue-green range up to room temperature. The active element is a CdSe quantum dot (QD) embedded in a bottom-up core-shell ZnSe nanowire grown by molecular beam epitaxy. The nanowire shell acts as a waveguide and confines the fundamental optical mode HE11, channelling the photons emitted by the QD along the nanowire axis. The nanowire has a base radius of 70-90 nm and a length of 5-6 µm with a conical ending that allows to adiabatically expands the guided mode and reduces the divergence angle. Photo-correlation measurements show anti-bunching with g(2)(0) values down to 0.3 at room temperature. Charged excitons degrade the emission properties at room temperature and we found that a neutral nanowire-quantum dot would emit single-photons with a brightness of 0.17 photon per pulse.
12993-28
10 April 2024 • 11:20 - 11:40 CEST | Londres 1/Salon 8, Niveau/Level 0
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In this talk we will give a short insight on our work done on single photon emitters hosted in hexagonal Boron Nitride (hBN) and integrated photonics chips utilising those.
We have recently shown the deterministic creation of near-ideal single photon emitters at room temperature and have now worked more on the identification of their atomic origin comparing optical characteristics with density functional theory calculations.
For the practical usage of single photon emitters we have been working on integrated photonics chips based around laser written waveguides that can be used for various applications including tests on the fundamentals of quantum mechanics and quantum communication.
12993-29
10 April 2024 • 11:40 - 12:00 CEST | Londres 1/Salon 8, Niveau/Level 0
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We present a turn-key portable picosecond fiber laser for efficient quantum dot excitation to generate single photons. The laser combines a mode-hop-free tunability in the regions 770-980 nm and 1150-1500 nm with a high pulse-to-pulse coherence of 98%. A high single photon purity and indistinguishability were demonstrated. An excellent long-term power stability with a standard deviation of less than 0.3% and wavelength stability of better than 5 pm were achieved. The laser enables excitation of different semiconductor quantum dots and excitation schemes, essential for versatile easy-to-use single-photon sources based on quantum dots for research applications and commercial quantum computing.
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