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« C'est avec la logique que nous prouvons et avec l'intuition que nous trouvons. » – Henri Poincaré
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80
Doctorats
3356
Citations
74
Publications
8
Équipes de recherche
Efficient training of photonic quantum generative models
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We present an efficient training method for photonic quantum generative models based on maximum mean discrepancy (MMD). The approach enables gradient-based optimization on classical hardware while preserving quantum photonic deployment through boson sampling. Our results show that large photon-native models can be trained efficiently in practice, supporting scalable photonic quantum machine learning.
MerLin: A Discovery Engine for Photonic and Hybrid Quantum Machine Learning
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Identifying where quantum models may offer practical benefits in near-term QML requires systematic, reproducible benchmarking across models, datasets, and hardware constraints. MerLin is an open-source discovery engine for photonic and hybrid quantum machine learning, integrating optimized strong simulation of linear-optical circuits into PyTorch and scikit-learn workflows for end-to-end differentiable training. To establish a shared empirical baseline, MerLin ships 18 reproduced state-of-the-art photonic and hybrid QML studies as modular, reusable experiments, and includes hardware-aware features for testing on available photonic quantum processors—positioning it as a future-proof co-design tool linking algorithms, benchmarks, and hardware.
Exponential improvement in benchmarking multiphoton interference
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Several photonic quantum technologies rely on the ability to generate multiple indistinguishable photons. Benchmarking the level of indistinguishability of these photons is essential for scalability. The Hong-Ou-Mandel dip provides a benchmark for the indistinguishability between two photons, and extending this test to the multi-photon setting has so far resulted in a protocol that computes the genuine n-photon indistinguishability (GI). However, this protocol has a sample complexity that increases exponentially with the number of input photons for an estimation of GI up to a given additive error. To address this problem, we introduce new theorems that strengthen our understanding of the relationship between distinguishability and the suppression laws of the quantum Fourier transform interferometer (QFT). Building on this, we propose a protocol using the QFT for benchmarking GI that achieves constant sample complexity for the estimation of GI up to a given additive error for prime photon numbers, and sub-polynomial scaling otherwise, representing an exponential improvement over the state of the art. We prove the optimality of our protocol in many relevant scenarios and validate our approach experimentally on Quandela’s reconfigurable photonic quantum processor, where we observe a clear advantage in runtime and precision over the state of the art. We therefore establish the first scalable method for computing multi-photon indistinguishability, which applies naturally to current and near-term photonic quantum hardware.
Quantum Energetic Advantage before Computational Advantage in Boson Sampling
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We analyze the energy efficiency of photonic quantum computers for Boson Sampling using a realistic architecture and the Metric-Noise-Resource methodology. By connecting control parameters, noise, and energetic resources, we identify operating regimes that minimize energy cost per sample. Our results demonstrate a quantum energetic advantage over classical implementations, achievable even before computational speedup. We propose a feasible architecture with a complete noise and loss budget to enable near-term experimental observation of this advantage.
Towards practical secure delegated quantum computing with semi-classical light
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We present a secure delegated quantum computing protocol that replaces demanding client-side quantum hardware with semi-classical light. The client only uses attenuated laser pulses, while the server uses interacting quantum emitters to convert those pulses into photonic qubits and generate entanglement. The protocol preserves information-theoretic composable security and brings secure delegated quantum computing closer to practical photonic implementation.
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Establishing Baselines for Photonic Quantum Machine Learning: Insights from an Open, Collaborative Initiative
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The Perceval Challenge is an open, reproducible benchmark designed to assess the potential of photonic quantum computing for machine learning. Focusing on a reduced and hardware-feasible version of the MNIST digit classification task or near-term photonic processors, it offers a concrete framework to evaluate how photonic quantum circuits learn and generalize from limited data. Conducted over more than three months, the challenge attracted 64 teams worldwide in its first phase. After an initial selection, 11 finalist teams were granted access to GPU resources for large-scale simulation and photonic hardware execution through cloud service. The results establish the first unified baseline of photonic machine-learning performance, revealing complementary strengths between variational, hardware-native, and hybrid approaches. This challenge also underscores the importance of open, reproducible experimentation and interdisciplinary collaboration, highlighting how shared benchmarks can accelerate progress in quantum-enhanced learning. All implementations are publicly available in a single shared repository (this https URL), supporting transparent benchmarking and cumulative research. Beyond this specific task, the Perceval Challenge illustrates how systematic, collaborative experimentation can map the current landscape of photonic quantum machine learning and pave the way toward hybrid, quantum-augmented AI workflows.
Enhanced Fault-tolerance in Photonic Quantum Computing: Comparing the Honeycomb Floquet Code and the Surface Code in Tailored Architecture
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Cited by 16
Fault-tolerant quantum computing is crucial for realizing large-scale quantum computation, and the interplay between hardware architecture and quantum error-correcting codes is a key consideration. We present a comparative study of two quantum error-correcting codes – the surface code and the honeycomb Floquet code – implemented on the spin-optical quantum computing architecture, either with controlled-Z operations or with direct parity measurements. This allows for a direct comparison of the codes using consistent noise models. Notably, we achieve a loss threshold of 6.3% with the honeycomb Floquet code implemented on our tailored architecture, almost twice as high as the loss threshold obtained with the surface code on the previous architecture, all the while requiring less physical qubits. This finding is particularly significant given that photon loss is the primary source of errors in photon-mediated quantum computing. Moreover, we benchmark the general performances of the two codes in a multi-error setting by computing the volume of the fault-tolerant region, and show that the fault-tolerant region of the honeycomb code is over twice as large as that of the surface code.
Resource-efficient crosstalk mitigation for the high-fidelity operation of photonic integrated circuits with induced phase shifters
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Photonic integrated circuits (PICs) are key platforms for the compact and stable manipulation of classical and quantum light. Imperfections arising from fabrication constraints, tolerances, and operation wavelength limit the accuracy of intended operations on light and impede the practical utility of current PICs. In particular, crosstalk between reconfigurable phase shifters is challenging to characterize due to the large number of parameters to estimate and the difficulty in isolating individual parameters. Previous studies have attempted to model crosstalk solely as an interaction between controlled phase shifters, overlooking the broader scope of this issue. We introduce the concept of induced phase shifter, arising from crosstalk on bare waveguide sections as predicted by simulations, resulting in an exhaustive description and systematic analysis of crosstalk. We characterize induced phase shifters in physical devices using a machine learning-based method and propose a mitigation framework. This framework further allows to establish a criterion certifying that a given interferometer has a sufficient number of degrees of freedom adequately laid out to fully mitigate crosstalk. Our approach is experimentally validated on a 12-mode Clements interferometer. We demonstrate the efficacy of our extended crosstalk model to accurately recover physical crosstalk properties of the PIC and cancel induced phase shifters following our mitigation framework.
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Monitoring the generation of photonic linear cluster states with partial measurements
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Quantum states of light with many entangled photons are key resources for photonic quantum computing and quantum communication. In this work, we exploit a highly resource-efficient generation scheme based on a linear optical circuit embedding a fibered delay loop acting as a quantum memory. The single photons are generated with a bright single-photon source based on a semiconductor quantum dot, allowing to perform the entangling scheme up to 6 photons. We demonstrate , , and -photon entanglement generation at respective rates of kHz, Hz, Hz, and mHz, corresponding to an average scaling ratio of . We introduce a method for real-time control of entanglement generation based on partially post-selected measurements. The visibility of such measurements carries faithful information to monitor the entanglement process, an important feature for the practical implementation of photonic measurement-based quantum computation.
Photon-native quantum algorithms
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Photonic platforms occupy a central place in quantum technologies. They appear in quantum networks and communication, in near-term quantum advantage schemes, as well as in fault-tolerant quantum computing proposals. In this perspective article, we review the advances and challenges of this technology, and we focus on algorithms and protocols that we call photon-native, i.e. which closely follow the specificities of the hardware.
Indistinguishability of remote quantum dot-cavity single-photon sources
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Generating identical photons from remote emitter-based bright single-photon sources is an important step for scaling up optical quantum technologies. Here, we study the Hong-Ou-Mandel interference of photons emitted from remote sources based on semiconductor quantum dots. We make use of a deterministic fabrication technique to position the quantum dots in a spectrally resonant micropillar cavity and fine tune their operation wavelength electrically. Doing so, we can match four pairs of sources between five distinct sources, study them under various excitation schemes and measure their degree of indistinguishability. We demonstrate remote indistinguishabiltiy between 44±1% and 69±1% depending on the pair of sources and excitation conditions, record values for quantum dots in cavities. The relative contribution of pure dephasing and spectral diffusion is then analysed, revealing that the remaining distinguishability is mostly due to low frequency noise
Minimizing resource overhead in fusion-based quantum computation using hybrid spin-photon devices
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Cited by 3
We present three schemes for constructing a (2,2)-Shor-encoded 6-ring photonic resource state for fusion-based quantum computing, each relying on a different type of photon source. We benchmark these architectures by analyzing their ability to achieve the best-known loss tolerance threshold for fusion-based quantum computation using the target resource state. More precisely, we estimate their minimum hardware requirements for fault-tolerant quantum computation in terms of the number of photon sources to achieve on-demand generation of resource states with a desired generation period. Notably, we find that a group of 12 deterministic single-photon sources containing a single matter qubit degree of freedom can produce the target resource state near-deterministically by exploiting entangling gates that are repeated until success. The approach is fully modular, eliminates the need for lossy large-scale multiplexing, and reduces the overhead for resource-state generation by several orders of magnitude compared to architectures using heralded single-photon sources and probabilistic linear-optical entangling gates. Our work shows that the use of deterministic single-photon sources embedding a qubit substantially shortens the path toward fault-tolerant photonic quantum computation.
Quantum interferences and gates with emitter-based coherent photon sources
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Cited by 2
Quantum emitters such as quantum dots, defects in diamond or in silicon have emerged as efficient single photon sources that are progressively exploited in quantum technologies. In 2019, it was shown that the emitted single photon states often include coherence with the vacuum component. Here we investigate how such photon-number coherence alters quantum interference experiments that are routinely implemented both for characterising or exploiting the generated photons. We show that it strongly modifies intensity correlation measurements in a Hong-Ou-Mandel experiment and leads to errors in indistinguishability estimations. It also results in additional entanglement when performing partial measurements. We illustrate the impact on quantum protocols by evidencing modifications in heralding efficiency and fidelity of two-qubit gates.
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Quantum circuit compression using qubit logic on qudits
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Cited by 2
We present qubit logic on qudits (QLOQ), a compression scheme in which the qubits from a hardware agnostic circuit are divided into groups of various sizes, and each group is mapped to a physical qudit for computation. QLOQ circuits have qubit-logic inputs, outputs, and gates, making them compatible with existing qubit-based algorithms and Hamiltonians. We show that arbitrary qubit-logic unitaries can in principle be implemented with significantly fewer two-level (qubit) physical entangling gates in QLOQ than in qubit encoding. We achieve this advantage in practice for two applications: variational quantum algorithms, and unitary decomposition. The variational quantum eigensolver (VQE) for LiH took 5 hours using QLOQ on one of Quandela’s cloud-accessible photonic quantum computers, whereas it would have taken 4.39 years in qubit encoding. We also provide a QLOQ version of the Quantum Shannon Decomposition, which not only outperforms previous qudit-based proposals, but also beats the theoretical lower bound on the CNOT cost of unitary decomposition in qubit encoding.
Deterministic and reconfigurable graph state generation with a single solid-state quantum emitter
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Cited by 14
Measurement-based quantum computing offers a promising route towards scalable, universal photonic quantum computation. This approach relies on the deterministic and efficient generation of photonic graph states in which many photons are mutually entangled with various topologies. Recently, deterministic sources of graph states have been demonstrated with quantum emitters in both the optical and microwave domains. In this work, we demonstrate deterministic and reconfigurable graph state generation with optical solid-state integrated quantum emitters. Specifically, we use a single semiconductor quantum dot in a cavity to generate caterpillar graph states, the most general type of graph state that can be produced with a single emitter. By using fast detuned optical pulses, we achieve full control over the spin state, enabling us to vary the entanglement topology at will. We perform quantum state tomography of two successive photons, measuring Bell state fidelities up to 0.80±0.04 and concurrences up to 0.69±0.09, while maintaining high photon indistinguishability. This simple optical scheme, compatible with commercially available quantum dot-based single photon sources, brings us a step closer to fault-tolerant quantum computing with spins and photons.
Efficient fiber-pigtailed source of indistinguishable single photons
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Cited by 7
Semiconductor quantum dots in microcavities are an excellent platform for the efficient generation of indistinguishable single photons. However, their use in a wide range of quantum technologies requires their controlled fabrication and integration in compact closed-cycle cryocoolers, with a key challenge being the efficient and stable extraction of the single photons into a single-mode fiber. Here we report on a novel method for fiber-pigtailing of deterministically fabricated single-photon sources. Our technique allows for nanometer-scale alignment accuracy between the source and a fiber, alignment that persists all the way from room temperature to 2.4 K. We demonstrate high performance of the device under near-resonant optical excitation with g(2)(0) = 1.3 %, a photon indistinguishability of 97.5 % and a fibered brightness of 20.8 %. We show that the indistinguishability and single-photon rate are stable for over ten hours of continuous operation in a single cooldown. We further confirm that the device performance is not degraded by nine successive cooldown-warmup cycles.
On the role of coherence for quantum computational advantage
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Quantifying the resources available to a quantum computer appears to be necessary to separate quantum from classical computation. Among them, entanglement, magic and coherence are arguably of great significance. We introduce path coherence as a measure of the coherent paths interferences arising in a quantum computation. Leveraging the sum-over-paths formalism, we obtain a classical algorithm for estimating quantum transition amplitudes, the complexity of which scales with path coherence. As path coherence relates to the hardness of classical simulation, it provides a new perspective on the role of coherence in quantum computational advantage. Beyond their fundamental significance, our results have practical applications for simulating large classes of quantum computations with classical computers.
Enhanced Fault-tolerance in Photonic Quantum Computing: Floquet Code Outperforms Surface Code in Tailored Architecture
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Cited by 13
Fault-tolerant quantum computing is crucial for realizing large-scale quantum computation, and the interplay between hardware architecture and quantum error-correcting codes is a key consideration. We present a comparative study of two quantum error-correcting codes – the surface code and the honeycomb Floquet code – implemented on variants of the spin-optical quantum computing architecture, enabling a direct comparison of the codes using consistent noise models. Our results demonstrate that the honeycomb Floquet code significantly outperforms the surface code in this setting. Notably, we achieve a photon loss threshold of 6.4% for the honeycomb Floquet code implementation – to our knowledge the highest reported for photonic platforms to date without large-scale multiplexing. This finding is particularly significant given that photon loss is the primary source of errors in photon-mediated quantum computing.
A deterministic and efficient source of frequency-polarization hyper-encoded photonic qubits
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Cited by 1
The frequency or color of photons is an attractive degree of freedom to encode and distribute the quantum information over long distances. However, the generation of frequency-encoded photonic qubits has so far relied on probabilistic non-linear single-photon sources and inefficient gates. Here, we demonstrate the deterministic generation of photonic qubits hyper-encoded in frequency and polarization based on a semiconductor quantum dot in a cavity. We exploit the double dipole structure of a neutral exciton and demonstrate the generation of any quantum superposition in amplitude and phase, controlled by the polarization of the pump laser pulse. The source generates frequency-polarization single-photon qubits at a rate of 4 MHz corresponding to a generation probability at the first lens of 28 ± 2%, with a photon number purity > 98%. The photons show an indistinguishability > 91% for each dipole and 88% for a balanced quantum superposition of both. The density matrix of the hyper-encoded photonic state is measured by time-resolved polarization tomography, evidencing a fidelity to the target state of 94 ± 8% and concurrence of 77 ± 2%, here limited by frequency overlap in our device. Our approach brings the advantages of quantum dot sources to the field of quantum information processing based on frequency encoding.
A photonic parameter-shift rule: enabling gradient computation for photonic quantum computers
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Cited by 3
We present a method for gradient computation in quantum algorithms implemented on linear optical quantum computing platforms. While parameter-shift rules have become a staple in qubit gate-based quantum computing for calculating gradients, their direct application to photonic platforms has been hindered by the non-unitary nature of differentiated phase-shift operators in Fock space. We introduce a photonic parameter-shift rule that overcomes this limitation, providing an exact formula for gradient computation in linear optical quantum processors. Our method scales linearly with the number of input photons and utilizes the same parameterized photonic circuit with shifted parameters for each evaluation. This advancement bridges a crucial gap in photonic quantum computing, enabling efficient gradient-based optimization for variational quantum algorithms on near-term photonic quantum processors. We demonstrate the efficacy of our approach through numerical simulations in quantum chemistry and generative modeling tasks, showing superior optimization performance as well as robustness to noise from finite sampling and photon distinguishability compared to other gradient-based and gradient-free methods.
Towards quantum advantage with photonic state injection
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Cited by 4
We propose a new scheme for near-term photonic quantum device that allows to increase the expressive power of the quantum models beyond what linear optics can do. This scheme relies upon state injection, a measurement-based technique that can produce states that are more controllable, and solve learning tasks that are not believed to be tackled classically. We explain how circuits made of linear optical architectures separated by state injections are keen for experimental implementation. In addition, we give theoretical results on the evolution of the purity of the resulting states, and we discuss how it impacts the distinguishability of the circuit outputs. Finally, we study a computational subroutines of learning algorithms named probability estimation, and we show the state injection scheme we propose may offer a potential quantum advantage in a regime that can be more easily achieved that state-of-the-art adaptive techniques. Our analysis offers new possibilities for near-term advantage that require to tackle fewer experimental difficulties.
Towards practical secure delegated quantum computing with semi-classical light
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Cited by 1
Secure Delegated Quantum Computation (SDQC) protocols are a vital piece of the future quantum information processing global architecture since they allow end-users to perform their valuable computations on remote quantum servers without fear that a malicious quantum service provider or an eavesdropper might acquire some information about their data or algorithm. They also allow end-users to check that their computation has been performed as they have specified it. However, existing protocols all have drawbacks that limit their usage in the real world. Most require the client to either operate a single-qubit source or perform single-qubit measurements, thus requiring them to still have some quantum technological capabilities albeit restricted, or require the server to perform operations which are hard to implement on real hardware (e.g isolate single photons from laser pulses and polarisation-preserving photon-number quantum non-demolition measurements). Others remove the need for quantum communications entirely but this comes at a cost in terms of security guarantees and memory overhead on the server’s side. We present an SDQC protocol which drastically reduces the technological requirements of both the client and the server while providing information-theoretic composable security. More precisely, the client only manipulates an attenuated laser pulse, while the server only handles interacting quantum emitters with a structure capable of generating spin-photon entanglement. The quantum emitter acts as both a converter from coherent laser pulses to polarisation-encoded qubits and an entanglement generator. Such devices have recently been used to demonstrate the largest entangled photonic state to date, thus hinting at the readiness of our protocol for experimental implementations.
Entanglement-enhanced Quantum Reinforcement Learning: an Application using Single-Photons
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Cited by 1
Quantum Reinforcement Learning (QRL) is an emerging field with many novel approaches suitable for noisy intermediate-scale quantum (NISQ) devices being proposed recently. Projective Simulation (PS) is a classical machine learning method based on random walks in a Directed Acyclic Graph (DAG), and is mainly used to train agents in a Reinforcement Learning setup. This graph corresponds to the Episodic Compositional Memory (ECM) of the agent. For the quantum version of PS we use quantum walks of single photons in quantum optical circuits, which go through tunable components (beamsplitters and phase shifters). We call this specific model Quantum Optical Projective Simulation (QOPS). In this work, we propose a general framework to translate any 2-layer ECM to a quantum optical circuit and an algorithm for solving quantum strategic games using QOPS. Moreover, we introduce QOPS with an entangled state as input. The application that we are using to evaluate the performance of the framework is the Prisoner’s Dilemma. We executed the implementation using Altair’s noisy simulator, designed to emulate a single photon-based quantum processor by Quandela. The algorithm provided promising results even in the presence of noise, which makes it a strong candidate for runs on single-photon-based quantum processors.
Connecting quantum circuit amplitudes and matrix permanents through polynomials
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In this paper, we strengthen the connection between qubit-based quantum circuits and photonic quantum computation. Within the framework of circuit-based quantum computation, the sum-over-paths interpretation of quantum probability amplitudes leads to the emergence of sums of exponentiated polynomials. In contrast, the matrix permanent is a combinatorial object that plays a crucial role in photonic by describing the probability amplitudes of linear optical computations. To connect the two, we introduce a general method to encode an F2-valued polynomial with complex coefficients into a graph, such that the permanent of the resulting graph’s adjacency matrix corresponds directly to the amplitude associated the polynomial in the sum-over-path framework. This connection allows one to express quantum amplitudes arising from qubit-based circuits as permanents, which can naturally be estimated on a photonic quantum device.
Towards Photon-Number-Encoded High-dimensional Entanglement from a Sequentially Excited Quantum Three-Level System
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The sequential resonant excitation of a 2-level quantum system results in the emission of a state of light showing time-entanglement encoded in the photon-number-basis – notions that can be extended to 3-level quantum systems as discussed in a recent proposal. Here, we report the experimental implementation of a sequential two-photon resonant excitation process of a solid-state 3-level system, constituted by the biexciton-, exciton-, and ground-state of a semiconductor quantum dot. The resulting light state exhibits entanglement in time and energy, encoded in the photon-number basis, which could be used in quantum information applications, e.g., dense information encoding or quantum communication protocols. Performing energy- and time-resolved correlation experiments in combination with extensive theoretical modelling, we are able to partially retrieve the entanglement structure of the generated state.
High-fidelity four-photon GHZ states on chip
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Cited by 22
Mutually entangled multi-photon states are at the heart of all-optical quantum technologies. While impressive progresses have been reported in the generation of such quantum light states using free space apparatus, high-fidelity high-rate on-chip entanglement generation is crucial for future scalability. In this work, we use a bright quantum-dot based single-photon source to demonstrate the high fidelity generation of 4-photon Greenberg-Horne-Zeilinger (GHZ) states with a low-loss reconfigurable glass photonic circuit. We reconstruct the density matrix of the generated states using full quantum-state tomography reaching an experimental fidelity to the target state of , and a purity of . The entanglement of the generated states is certified with a semi device-independent approach through the violation of a Bell-like inequality by more than 39 standard deviations. Finally, we carry out a four-partite quantum secret sharing protocol on-chip where a regulator shares with three interlocutors a sifted key with up to 1978 bits, achieving a qubit-error rate of 10.87%. These results establish that the quantum-dot technology combined with glass photonic circuitry offers a viable path for entanglement generation and distribution.
Photonic quantum generative adversarial networks for classical data
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Cited by 3
In generative learning, models are trained to produce new samples that follow the distribution of the target data. These models were historically difficult to train, until proposals such as Generative Adversarial Networks (GANs) emerged, where a generative and a discriminative model compete against each other in a minimax game. Quantum versions of the algorithm were since designed, both for the generation of classical and quantum data. While most work so far has focused on qubit-based architectures, in this article we present a quantum GAN based on linear optical circuits and Fock-space encoding, which makes it compatible with near-term photonic quantum computing. We demonstrate that the model can learn to generate images by training the model end-to-end experimentally on a single-photon quantum processor.
Mitigating photon loss in linear optical quantum circuits: classical post processing methods outperforming post selection
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Cited by 7
We develop classical postprocessing techniques to mitigate the effects of photon loss, and show that these outperform existing strategies of dealing with loss such as post-selection. Our approach significantly enhances the performance of photonic quantum systems by addressing one of the key challenges in photonic quantum computing. We demonstrate how these techniques can be applied to various photonic quantum algorithms, improving their robustness and reliability in practical implementations.
Simple rules for two-photon state preparation with linear optics
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Cited by 2
We derive necessary and sufficient conditions for two-photon entanglement in linear optics. We characterize input states for arbitrary two-qudit preparation in d-rail encoding and determine auxiliary photon requirements for heralded two-photon state preparation. We present a construction for generalized post-selected n-qubit control-rotation gates. Our findings advance probabilistic entanglement methods for quantum communication and computation, enhancing the toolkit for photonic quantum information processing.
Faster and shorter synthesis of Hamiltonian simulation circuits
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Cited by 7
We develop greedy heuristics for quantum circuit synthesis of Pauli rotations, optimizing for minimal entangling gate count or depth with flexible rotation ordering options. Our benchmarks show up to 4x depth reduction compared to state-of-the-art Hamiltonian simulation circuits. This approach is applicable to generic quantum circuit optimization via decomposition and resynthesis, advancing quantum circuit design efficiency.
An error-mitigated photonic quantum circuit Born machine
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Cited by 3
We introduce a photonic version of a quantum circuit Born machine, a type of quantum generative model, and show that applying our newly developed photon loss mitigation technique allows recovering trainability of this model in realistic lossy scenarios. Our work advances photonic quantum machine learning capabilities by addressing the critical challenge of photon loss. We demonstrate the effectiveness of our approach in enhancing the performance and practical applicability of quantum generative models on photonic platforms.
Verification of Quantum Computations without Trusted Preparations or Measurements
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Cited by 6
We introduce novel quantum verification protocols. Our first protocol reduces BQP verification to trusted Z-axis rotations and bit flips. The second enables verification of arbitrary quantum computations without trusted preparations or measurements, achieving information-theoretic security. This protocol requires the verifier to perform multi-qubit gates on a size-independent register. We advance Secure Delegated Quantum Computing, settling the open question on universal quantum computation verification with a modular, composable, and efficient approach to transform existing schemes.
Four-photon GHZ states generated on a laser written integrated platform
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We present an experiment where a reconfigurable photonic processor fabricated in glass by femtosecond laser micromachining is used for the generation of four-photons GHZ entangled states, with high efficiency and fidelity. The chip is used in synergy with a bright and quasi-deterministic source of single photons based on semiconductor quantum dot. The very efficient interfacing of these two platforms is ensured by the excellent connectivity between glass photonic circuits and standard optical fibers. In addition, in order to benchmark the quality of the generated states, this processor is used to implement a quantum secret sharing protocol on chip.
Quantum bounds for compiled XOR games and d-outcome CHSH games
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Cited by 6
Nonlocal games play a crucial role in quantum information theory and have numerous applications in certification and cryptographic protocols. Kalai et al. (STOC 2023) introduced a procedure to compile a nonlocal game into a single-prover interactive proof, using a quantum homomorphic encryption scheme, and showed that their compilation method preserves the classical bound of the game. Natarajan and Zhang (FOCS 2023) then showed that the quantum bound is preserved for the specific case of the CHSH game. Extending the proof techniques of Natarajan and Zhang, we show that the compilation procedure of Kalai et al. preserves the quantum bound for two classes of games: XOR games and d-outcome CHSH games. We also establish that, for any pair of qubit measurements, there exists an XOR game such that its optimal winning probability serves as a self-test for that particular pair of measurements.
A Complete Graphical Language for Linear Optical Circuits with Finite-Photon-Number Sources and Detectors
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Cited by 2
Linear optical circuits can be used to manipulate the quantum states of photons as they pass through components including beam splitters and phase shifters. Those photonic states possess a particularly high level of expressiveness, as they reside within the bosonic Fock space, an infinite-dimensional Hilbert space. However, in the domain of linear optical quantum computation, these basic components may not be sufficient to efficiently perform all computations of interest, such as universal quantum computation. To address this limitation it is common to add auxiliary sources and detectors, which enable projections onto auxiliary photonic states and thus increase the versatility of the processes. In this paper, we introduce the LOfi-calculus, a graphical language to reason on the infinite-dimensional bosonic Fock space with circuits composed of four core elements of linear optics: the phase shifter, the beam splitter, and auxiliary sources and detectors with bounded photon number. We present an equational theory that we prove to be complete: two LOfi-circuits represent the same quantum process if and only if one can be transformed into the other with the rules of the LOfi-calculus. We give a unique and compact universal form for such circuits.
Spin Noise Spectroscopy of a Single Spin using Single Detected Photons
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Cited by 5
Spin noise spectroscopy has become a widespread technique to extract information on spin dynamics in atomic and solid-state systems, in a potentially non-invasive way, through the optical probing of spin fluctuations. Here we experimentally demonstrate a new approach in spin noise spectroscopy, based on the detection of single photons. Due to the large spin-dependent polarization rotations provided by a deterministically-coupled quantum dot-micropillar device, giant spin noise signals induced by a single-hole spin are extracted in the form of photon-photon cross-correlations. Ultimately, such a technique can be extended to an ultrafast regime probing mechanisms down to few tens of picoseconds.
Solid‐State Single‐Photon Sources: Recent Advances for Novel Quantum Materials
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Cited by 59
In this review, we describe the current landscape of emergent quantum materials for quantum photonic applications. We focus on three specific solid-state platforms: single emitters in monolayers of transition metal dichalcogenides, defects in hexagonal boron nitride, and colloidal quantum dots in perovskites. These platforms share a unique technological accessibility, enabling the rapid implementation of testbed quantum applications, all while being on the verge of becoming technologically mature enough for a first generation of real-world quantum applications. The review begins with a comprehensive overview of the current state-of-the-art for relevant single-photon sources in the solid-state, introducing the most important performance criteria and experimental characterization techniques along the way. We then benchmark progress for each of the three novel materials against more established (yet complex) platforms, highlighting performance, material-specific advantages, and giving an outlook on quantum applications. This review will thus provide the reader with a snapshot on latest developments in the fast-paced field of emergent single-photon sources in the solid-state, including all the required concepts and experiments relevant to this technology.
Photonic quantum interference in the presence of coherence with vacuum
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Cited by 3
We study the impact of coherence with vacuum in photonic states emitted by quantum emitters such as atoms or quantum dots. We examine how this superposition of vacuum and one-photon components affects photonic quantum information processing. Our investigation begins with Hong-Ou-Mandel (HOM) interference, a fundamental process in quantum photonic technology. We analyze the implications of this coherence on the performance and fidelity of quantum operations, providing insights into the challenges and potential solutions for using these quantum emitters in practical quantum information applications
A Spin-Optical Quantum Computing Architecture
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Cited by 22
We have developed a novel fault-tolerant quantum computing architecture called Spin-Optical Quantum Computing (SPOQC). Fault-tolerant quantum computers, which actively correct errors, are essential for unlocking the full potential of quantum algorithms. This enables us to perform the most challenging quantum computations and surpass the capabilities of classical computers. Our SPOQC architecture combines the advantages of spin qubits and optical systems to achieve robust error correction and scalability, paving the way for practical, large-scale quantum computing.
Corrected Bell and Noncontextuality Inequalities for Realistic Experiments
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Cited by 12
We quantify and enhance the robustness of quantum contextuality. We propose measures for non-signaling/non-disturbance and measurement sharpness, and prove the continuity of contextual fraction. We establish bounds for assumption relaxations and introduce the notion of genuine contextuality resistant to experimental imperfections. Our findings apply to various existing results and experimental setups, advancing the understanding and practical application of contextuality in quantum information science.
Scalable machine learning-assisted clear-box characterization for optimally controlled photonic circuits
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Cited by 25
Machine learning-assisted method developed for photonic chip characterization. Scalable, iterative approach using virtual chip replica. Sample-efficient process requires only CW laser and powermeters. Estimates passive phases, crosstalk, beamsplitter reflectivity, relative I/O losses. Enables imperfection mitigation for enhanced device control. Validated on 12-mode Clements-interferometer with 126 phase shifters. Achieves 99.77% average amplitude fidelity for 100 Haar-random unitaries. Advances photonic integrated circuit performance for classical and quantum applications.
One nine availability of a Photonic Quantum Computer on the Cloud toward HPC integration
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Cited by 5
First cloud-accessible general-purpose single-photon quantum computer introduced. Designed for high availability and HPC environment compatibility. Achieved 92% uptime (one nine availability) over six months. Exceeds availability of most online quantum computing services. Addresses challenges of QC integration in HPC: stability, maintenance, heterogeneity. Advances quantum computing accessibility for hybrid HPC-QC infrastructures. Lays groundwork for real-world problem-solving using combined QC-HPC strengths.
Simulating photon counting from dynamic quantum emitters by exploiting zero-photon measurements
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Cited by 7
For designing and optimising photonic quantum technologies, numerical simulations are crucial. The Zero Photon Generator is a breakthrough method, which harnesses information from zero-photon measurements, to to give exponential speedup in time-integrated photon-counting simulations.
Quantum error-correcting codes with a covariant encoding
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Cited by 9
Given some group G of logical gates, for instance the Clifford group, what are the quantum encodings for which these logical gates can be implemented by simple physical operations, described by some physical representation of G? We study this question by constructing a general form of such encoding maps. For instance, we recover that the [[5,1,3]] and Steane codes admit transversal implementations of the binary tetrahedral and binary octahedral groups, respectively. For bosonic encodings, we show how to obtain the GKP and cat qudit encodings by considering the appropriate groups, and essentially the simplest physical implementations. We further illustrate this approach by introducing a 2-mode bosonic code defined from a constellation of 48 coherent states, for which all single-qubit Clifford gates correspond to passive Gaussian unitaries.
A versatile single-photon-based quantum computing platform
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Cited by 202
We introduce Quandela\’s Ascella quantum processor, a cloud-accessible versatile quantum computing platform based on single photons, and give a comprehensive overview of the software stack, benchmarks, as well as demonstrations of logic gates, algorithms, and building block operations for scalability. Our work showcases the capabilities of this advanced photonic quantum processor, highlighting its potential for both research and practical applications. We provide detailed performance metrics and demonstrate its ability to execute a range of quantum operations and algorithms.
Asymmetric Quantum Secure Multi-Party Computation With Weak Clients Against Dishonest Majority
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Cited by 10
We introduce a novel quantum Secure Multi-Party Computation (SMPC) protocol, lifting classical SMPC to the quantum realm. Our protocol is composably and statistically secure, even with a single honest party, and requires minimal quantum capabilities from clients: single-qubit X-Y plane state preparation. We leverage a new quantum verification technique in our modular construction, uncovering a fundamental invariance in measurement-based quantum computing. This work advances quantum secure multi-party computation capabilities.
Spin-photon entanglement and photonic cluster states generation with a semiconductor quantum dot in a cavity
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Semiconductor quantum dots have emerged as excellent artificial atoms to both generate and manipulate quantum light. When embedded in cavities, they can generate single photons and entangled photons with unparalleled efficiency and high quantum purity. In this talk, I will discuss how such devices can be used to generate strings of many entangled photons. The method, leveraging the spin-selective optical transition in a charged quantum dot, leads to the generation of indistinguishable photons in linear cluster states or GHZ states at high rates, realizing an important milestone for scaling-up optical quantum technologies.
Linear Optical Logical Bell State Measurements with Optimal Loss-Tolerance Threshold
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Cited by 15
Quantum threshold theorems impose hard limits on the hardware capabilities to process quantum information. We derive tight and fundamental upper bounds to loss-tolerance thresholds in different linear-optical quantum information processing settings through an adversarial framework, taking into account the intrinsically probabilistic nature of linear optical Bell measurements.
Solving graph problems with single-photons and linear optics
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Cited by 18
We demonstrate efficient encoding of n×n matrices into 2n-mode linear optical circuits, applying this technique to encode graph information matrices. We propose a photonic quantum processor design incorporating single-photon sources, encoded optical circuits, and single-photon detectors. Our approach solves various graph problems, including bipartite perfect matchings, permanental polynomials, graph isomorphism, and k-densest subgraph. We develop pre-processing methods to boost relevant detection probabilities and validate our findings through numerical simulations. This work advances practical applications for near-term quantum devices in graph theory and combinatorial optimization.
Certified randomness in tight space
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Cited by 14
Reliable randomness is a core ingredient in algorithms and applications ranging from numerical simulations to sampling and cryptography. The violation of a Bell inequality can certify that intrinsic randomness is being generated, but this certification typically requires spacelike separated devices. In this work, we provide new theoretical tools to certify randomness generation on a small-scale device and perform a first-of-its-kind integrated photonic demonstration combining a quantum dot based single-photon source and a reconfigurable glass chip.
High-fidelity generation of four-photon GHZ states on-chip
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Cited by 38
We demonstrate high-fidelity on-chip generation and characterization of a 4-photon Greenberger-Horne-Zeilinger (GHZ) state. Our approach combines a bright single-photon source based on a single quantum dot with a reconfigurable, low-loss laser-written photonic chip. This integration of deterministic single-photon emission and advanced photonic circuitry enables the creation of complex multi-photon entangled states with high efficiency. Our work advances the field of integrated quantum photonics, paving the way for scalable quantum information processing and communication applications on chip-scale devices.
Photonic Quantum Computing For Polymer Classification
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We present a hybrid classical-quantum approach to the binary classification of polymer structures. Two polymer classes visual (VIS) and near-infrared (NIR) are defined based on the size of the polymer gaps. The hybrid approach combines one of the three methods, Gaussian Kernel Method, Quantum-Enhanced Random Kitchen Sinks or Variational Quantum Classifier, implemented by linear quantum photonic circuits (LQPCs), with a classical deep neural network (DNN) feature extractor. The latter extracts from the classical data information about samples chemical structure. It also reduces the data dimensions yielding compact 2-dimensional data vectors that are then fed to the LQPCs. We adopt the photonic-based data-embedding scheme, proposed by Gan et al. [EPJ Quantum Technol. 9, 16 (2022)] to embed the classical 2-dimensional data vectors into the higher-dimensional Fock space. This hybrid classical-quantum strategy permits to obtain accurate noisy intermediate-scale quantum-compatible classifiers by leveraging Fock states with only a few photons. The models obtained using either of the three hybrid methods successfully classified the VIS and NIR polymers. Their accuracy is comparable as measured by their scores ranging from 0.86 to 0.88. These findings demonstrate that our hybrid approach that uses photonic quantum computing captures chemistry and structure-property correlation patterns in real polymer data. They also open up perspectives of employing quantum computing to complex chemical structures when a larger number of logical qubits is available.
High-rate entanglement between a semiconductor spin and indistinguishable photons
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Cited by 137
We present cluster states of entangled photons represent the main building block for developing error corrected and large scale photonic quantum computers. We demonstrate the generation of three-photon cluster states using a single quantum dot based device, achieving two orders of magnitude with respect to previous state of the art among different quantum technology systems.
Probing the dynamics and coherence of a semiconductor hole spin via acoustic phonon-assisted excitation
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Cited by 20
Spins in semiconductor quantum dots are promising local quantum memories to generate polarization-encoded photonic cluster states, as proposed in the pioneering Rudolph-Lindner scheme [1]. However, harnessing the polarization degree of freedom of the optical transitions is hindered by resonant excitation schemes that are widely used to obtain high photon indistinguishability. Here we show that acoustic phonon-assisted excitation, a scheme that preserves high indistinguishability, also allows to fully exploit the polarization selective optical transitions to initialise and measure single spin states. We access the coherence of hole spin systems in a low transverse magnetic field and directly monitor the spin Larmor precession both during the radiative emission process of an excited state or in the quantum dot ground state. We report a spin state detection fidelity of 94.7±0.2% granted by the optical selection rules and a 20±5~ns hole spin coherence time, demonstrating the potential of this scheme and system to generate linear cluster states with a dozen of photons
A Complete Equational Theory for Quantum Circuits
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Cited by 17
In this note, is introduced the first complete equational theory for quantum circuits. More precisely, a set of circuit equations that are proved to be sound and complete: two circuits represent the same quantum evolution if and only if they can be transformed one into the other using the equations.
Strong Simulation of Linear Optical Processes
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Cited by 25
An algorithm and general framework for the simulation of photons passing through linear optical interferometers.
A Framework for Verifiable Blind Quantum Computation
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Cited by 3
While it is possible to benchmark devices or use certification techniques under various assumptions, the most stringent proof is given by verification protocols: they provide unconditional assurance that the client will either receive the correct outcome or abort the computation, even against a service provider which actively tries to corrupt the result. We provide the first framework for designing such protocols in a way that both encompasses most known protocols and allows creating new ones in a much simpler way. This streamlines the creation process and allows us to already improve on our previous state-of-the-art protocols for the verification of delegated quantum computation by introducing two new constructions.
Energy-efficient quantum non-demolition measurement with a spin-photon interface
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Cited by 10
Spin-photon interfaces (SPIs) are key devices of quantum technologies, aimed at coherently transferring quantum information between spin qubits and propagating pulses of polarized light. We study the potential of a SPI for quantum non demolition (QND) measurements of a spin state. After being initialized and scattered by the SPI, the state of a light pulse depends on the spin state. It thus plays the role of a pointer state, information being encoded in the light’s temporal and polarization degrees of freedom. Building on the fully Hamiltonian resolution of the spin-light dynamics, we show that quantum superpositions of zero and single photon states outperform coherent pulses of light, producing pointer states which are more distinguishable with the same photon budget. The energetic advantage provided by quantum pulses over coherent ones is maintained when information on the spin state is extracted at the classical level by performing projective measurements on the light pulses. The proposed schemes are robust against imperfections in state of the art semi-conducting devices.
LOv-Calculus: A Graphical Language for Linear Optical Quantum Circuits
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Cited by 32
The LOv-calculus, a graphical language for reasoning about linear optical quantum circuits with so-called vacuum state auxiliary inputs.
Quantum Advantage in Information Retrieval
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Cited by 25
We introduce a related task to random access codes—the Torpedo Game—and show that it admits greater quantum advantage than the comparable random access code. Our work expands the scope of quantum communication advantages, providing new insights into information retrieval tasks. We demonstrate that this novel scenario offers enhanced performance over traditional random access codes, furthering our understanding of quantum communication capabilities.
Perceval: A Software Platform for Discrete Variable Photonic Quantum Computing
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Cited by 74
We introduce Perceval, an evolutive open-source software platform for simulating and interfacing with discrete variable photonic quantum computers, and describe its main features and components. Our platform provides researchers and developers with powerful tools for photonic quantum computing, offering simulation capabilities and interface options for real quantum systems. We detail the software\’s architecture and highlight its potential for advancing photonic quantum computing research and development.
Assessing the quality of near-term photonic quantum devices
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Cited by 10
We develop a certification method for photonic quantum devices, tailored for single photon sources, linear optical circuits, and detectors. We use BosonSampling output statistics and introduce the Photonic Quality Factor metric. Our benchmark tests target photon loss and distinguishability, providing evidence for non-classical simulability of passing experiments. We establish scaling requirements for photon loss rate and single-photon state fidelity, highlighting the eventual necessity of error correction for avoiding classical simulability.
Experimental Analysis of Energy Transfers between a Quantum Emitter and Light Fields
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Cited by 68
Energy transfer between quantum systems can either be achieved through an effective unitary interaction or through the generation of entanglement. This observation defines two types of energy exchange: unitary and correlation energy. Here we propose and implement experimental protocols to access these energy transfers in interactions between a quantum emitter and light fields. Upon spontaneous emission, we measure the unitary energy transfer from the emitter to the optical field and show that it never exceeds half of the total energy and is reduced when introducing decoherence. We then study the interference of the emitted field and a laser field at a beam splitter and show that the energy transfers quantitatively depend on the quantum purity of the emitted field.
Quantifying n-photon indistinguishability with a cyclic integrated interferometer
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Cited by 53
We report on a universal method to measure the genuine indistinguishability of n-photons – a crucial parameter that determines the accuracy of optical quantum computing. Our approach relies on a low-depth cyclic multiport interferometer with N = 2n modes, leading to a quantum interference fringe whose visibility is a direct measurement of the genuine n-photon indistinguishability. We experimentally demonstrate this technique for a 8-mode integrated interferometer fabricated using femtosecond laser micromachining and four photons from a quantum dot single-photon source. We measure a four-photon indistinguishability up to 0.81±0.03. This value decreases as we intentionally alter the photon pairwise indistinguishability. The low-depth and low-loss multiport interferometer design provides an efficient and scalable path to evaluate the genuine indistinguishability of resource states of increasing photon number.
Contextuality and Wigner Negativity Are Equivalent for Continuous-Variable Quantum Measurements
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Cited by 45
Equivalence demonstrated between contextuality and Wigner negativity in continuous-variable quantum computing. Unifies previously distinct quantum resources for speedup. Applicable to standard continuous-variable models. Facilitates practical demonstrations of continuous-variable contextuality. Illuminates role of negative probabilities in quantum phase-space representations. Advances understanding of quantum speedup mechanisms in continuous-variable paradigm.
Mitigating errors by quantum verification and post-selection
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Cited by 15
We introduce a new quantum error mitigation technique based on the accreditation protocol from quantum verification. Our method uses postselection to correct observable expectation values, addressing noise in preparations, gates, and measurements. We provide rigorous error mitigation guarantees under realistic assumptions, tailored for time-dependent behaviors with varying output states. We analyze sample complexity and validate our technique on current quantum hardware, advancing near-term quantum computing capabilities without full QEC overhead.
Photon-number entanglement generated by sequential excitation of a two-level atom
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Cited by 43
Exploiting the atomic behaviour of a semiconductor quantum dot in a cavity, we develop a novel protocol for the generation of photon number entangled states in the time basis: from a photon number Bell state up to a series of multi-temporal mode entangled states. The results demonstrate the possibility of using single-photon sources to encode quantum information in new ways.
Bright Polarized Single-Photon Source Based on a Linear Dipole
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Cited by 146
Bright emission of polarized single-photons from quantum dots is demonstrated by taking advantage of phonon-assisted relaxation and the intrinsic linear dipole structure of exciton states. By optical pumping of the exciton state along one of its dipoles we achieve high emission efficiency of indistinguishable photons with linear polarization degree up to 99%, without the need of complex cavity engineering.
Hong-Ou-Mandel Interference with Imperfect Single Photon Sources
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Cited by 105
Hong-Ou-Mandel interference is a cornerstone of optical quantum technologies. We explore both theoretically and experimentally how the nature of unwanted multi-photon components of single photon sources affect the interference visibility. We apply our approach to quantum dot single photon sources in order to access the mean wavepacket overlap of the single-photon component – an important metric to understand the limitations of current sources. We find that the impact of multi-photon events has thus far been underestimated, and that the effect of pure dephasing is even milder than previously expected.
Sequential generation of linear cluster states from a single photon emitter
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Cited by 175
We demonstrate single-mode linear cluster state generation using a quantum dot single-photon source and fiber loop entangling gate. Our architecture produces polarization-encoded, individually-addressable photons, achieving up to four-photon linear cluster states. It is programmable for arbitrary photon numbers and employs a resource-efficient approach with a single entangling gate. We advance photonic one-way quantum computing capabilities, utilizing the most efficient single-photon source technology to date.
Generation of non-classical light in a photon-number superposition
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Cited by 100
Quantum information can be encoded in several degrees of freedom of single photons; we demonstrate the possibility to generate pulses of light containing a superposition of Fock states of different photon number with high quantum purity. By varying the excitation regime we present the deterministic variation of the proportions in between Fock states |0>, |1> and |2>. The results show in this way a new degree of freedom for qubit encoding in quantum computing protocols.
Reproducibility of High-Performance Quantum Dot Single-Photon Sources
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Cited by 115
Solid-state quantum light emitters are ubiquitous quantum technology devices required for a large plethora of applications. Their integration in complex industrial systems is bounded by the improvement of their efficiency but also by reproducible and high-fidelity fabrication on a large scale. By leveraging the full potential of semiconductor processing and Quandela’s technology, we demonstrate the scalable and reproducible fabrication of a large set of devices with top performances.
Interfacing scalable photonic platforms: solid-state based multi-photon interference in a reconfigurable glass chip
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Cited by 55
We demonstrate an efficient realization of a modular quantum photonic platform, interconnecting quantum dot single-photon emitters, active demultiplexing, and integrated waveguides on Silica. Our system leverages high brightness and device efficiency, achieving a significant speed-up compared to similar experiments using probabilistic Spontaneous Parametric Down-Conversion (SPDC) and four-wave mixing sources. This work advances the integration of deterministic single-photon sources with photonic circuits, enhancing the performance and scalability of quantum photonic technologies for practical applications in quantum information processing and communication.
Near-optimal single-photon sources in the solid state
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Cited by 1514
Single-photons are key elements of many future quantum technologies, be it for the realisation of large-scale quantum communication networks1 for quantum simulation of chemical and physical processes or for connecting quantum memories in a quantum computer. Scaling quantum technologies will thus require efficient, on-demand, sources of highly indistinguishable single-photons. Semiconductor quantum dots inserted in photonic structures are ultrabright single photon sources, but the photon indistinguishability is limited by charge noise induced by nearby surfaces. The current state of the art for indistinguishability are parametric down conversion single-photon sources, but they intrinsically generate multiphoton events and hence must be operated at very low brightness to maintain high single photon purity. To date, no technology has proven to be capable of providing a source that simultaneously generates near-unity indistinguishability and pure single-photons with high brightness. Here, we report on such devices made of quantum dots in electrically controlled cavity structures. We demonstrate on-demand, bright and ultra-pure single photon generation. Application of an electrical bias on deterministically fabricated devices is shown to fully cancel charge noise effects. Under resonant excitation, an indistinguishability of 0.9956±0.0045 is evidenced with a g(2)(0)=0.0028±0.0012. The photon extraction of 65% and measured brightness of 0.154±0.015 make this source 20 times brighter than any source of equal quality. This new generation of sources open the way to a new level of complexity and scalability in optical quantum manipulation.
Nos équipes de recherche
Les Quandeliens forment un groupe multidisciplinaire, international et talentueux de professionnels performants qui abordent les défis sous différents angles. Nous pensons que Quandela est un endroit unique où travailler. Notre équipe couvre un large éventail de lieux, de modes de vie et de parcours. Ensemble, nous créons un environnement de travail où chacun se sent en sécurité. Nous accueillons et respectons toujours l’individualité, car c’est ainsi que nous renforçons l’importance d’une équipe diversifiée, d’une équipe encouragée à grandir et à évoluer.
Recherche – Algorithmes
L’équipe Algorithmes développe, optimise et met en œuvre des algorithmes quantiques de pointe adaptés au matériel de Quandela. Elle se concentre sur des applications et des innovations dans le domaine de l'informatique quantique photonique, comblant ainsi le fossé entre le potentiel théorique et la mise en œuvre pratique.
« Les algorithmes quantiques photoniques transforment le potentiel de la mécanique quantique en informations exploitables, libérant la puissance des photons pour résoudre des problèmes complexes et ouvrir la voie aux percées quantiques de demain. »
Pierre-Emmanuel Emeriau – Chef de l’équipe algorithmes
Recherche – Théorie des dispositifs
L’équipe Théorie des dispositifs améliore les performances des dispositifs grâce à des modelés théoriques rigoureux, des simulations informatiques, des protocoles d’atténuation des erreurs et des techniques d'analyse comparative. Elle applique des mathématiques avancées pour affiner les expériences et repousser les limites des performances des dispositifs quantiques.
« Les mathématiques affinent notre compréhension de la physique, transformant les lois quantiques fondamentales en outils pour faire progresser le matériel, affiner les expériences et repousser les limites de la performance des dispositifs quantiques.»
Stephen Wein – Chef de l’équipe de théorie des dispositifs
Recherche – Architecture évolutive
L’équipe Architecture évolutive étudie la manière d'organiser et d'exploiter la technologie pionnière de Quandela afin d'effectuer des calculs quantiques importants et fiables. Ses domaines d'expertise comprennent la compilation, le calcul délégué et la correction d'erreurs quantiques.
« Une bonne architecture est un pont entre la physique compliquée et l'informatique abstraite. Elle orchestre les spins et les photons afin d’exécuter des calculs aussi longtemps que possible et sur autant de qubits que possible, à la fois dans le monde actuel pré-tolérant aux erreurs et dans le futur avec la correction des erreurs. »
Boris Bourdoncle – Chef de l’équipe d’architecture évolutive
Recherche – Semi-conducteurs
L’équipe Semi-conducteurs se concentre sur le développement d'approches innovantes pour optimiser les performances des sources de photons uniques à semi-conducteur. Elle explore de nouvelles conceptions de sources et des schémas d'adressage avances, dans le but de produire à grande échelle des sources de photons uniques hautement performantes pour des systèmes d'informatique quantique photonique tolérants aux erreurs.
« Notre objectif est de trouver de nouvelles méthodes pour créer de grands états intriqués de photons avec une probabilité et une fidélité élevées. En tant qu’élément clé du laboratoire commun formé par Quandela et le C2N, l’équipe sert également de lien important entre Quandela et le groupe universitaire GOSS dirigé par Pascale Senellart. »
Sebastien Boissier – Chef de l’équipe Semi-conducteurs
Applications quantiques
L’équipe Applications quantiques comble le fossé entre les cas d'utilisation de l'industrie, les algorithmes d'informatique quantique de pointe et l’intégration des produits. En concevant et en améliorant des algorithmes de pointe, elle renforce la confiance envers les applications photoniques quantiques pour résoudre des problèmes concrets, soutenant ainsi les clients dans leur parcours de transformation quantique.
« Nous soutenons nos clients dans leur transformation quantique. Nous offrons des cours sur l'informatique quantique photonique, nous identifions les cas d'utilisation au sein de l'industrie du client et nous développons des preuves de concept qui évoluent ensuite vers un algorithme en production. Tous ces ingrédients sont essentiels pour que les grandes entreprises réussissent leur transformation quantique. »
Arno Ricou – Chef de l’équipe des applications quantiques
Produits – Optique, électronique et assemblage QPU
L’équipe développe des systèmes optiques de pointe et des méthodes de contrôle optimales pour l'informatique quantique photonique. Elle intègre et assemble ces composants pour créer MosaiQ, soit des unités de traitement quantique (QPU) prêtes pour les centres de données. Les travaux de l’équipe sont essentiels pour faire progresser l’évolutivité et l’efficacité des ordinateurs quantiques photoniques.
« L'évolutivité des ordinateurs quantiques photoniques dépend de notre capacité à fabriquer des systèmes opto-électroniques complexes. En repoussant les limites de la fabrication de circuits intégrés photoniques, nous ne faisons pas qu'augmenter le nombre de qubits, nous améliorons également la précision et l’efficacité des opérations quantiques. Le passage à la fabrication à grande échelle de ces systèmes complexes sera la clé pour libérer tout le potentiel de l'informatique quantique photonique. »
Nicolas Maring – Chef de l’équipe Assemblage optique, électronique et QPU
Produits – Production de sources semi-conductrices
L'équipe Production de sources semi-conductrices produit l'une des sources quantiques à photon unique les plus brillantes au monde, grâce à des technologies de nanofabrication de pointe. Dans chaque ordinateur quantique, leur source sert de cœur, délivrant des photons uniques à travers les canaux de fibre optique et les circuits du QPU. Tout comme il n'existe pas de substitut pour un véritable cœur, leur source de photons est irremplaçable !
« Se dépasser et sl'encourager chaque jour, c’est ça l'art d’améliorer les choses ! »
Thi Huong Au – Chef de l’équipe de production des sources de semi-conducteurs
Logiciels – Ingénieurs logiciels
L’équipe Ingénieurs logiciels développe le cadre d'informatique quantique Perceval et gère l'infrastructure Web et infonuagique de Quandela. ElleIls joue un double rôle : diriger la production de logiciels via des mises à jour régulières pour Perceval et de nouvelles API pour les clients, tout en fournissant un soutien interne aux autres équipes via le développement d'outils et la révision de codes.
« Les gens s'imaginent que piloter un ordinateur quantique est quelque chose d’extrêmement compliqué, et c'est en partie vrai. Dans notre équipe, nous nous efforçons de transformer cela en une ‘simple’ opération complexe, soit en simplifiant chaque élément autant que possible. Il s'agit d'utiliser Python, puis d'envoyer un ordre de calcul via le Web à nos ordinateurs quantiques ou à des simulateurs optimisés. »
Mario Valdivia – Chef de l’équipe Ingénieurs logiciels