arXiv subjects

Emmanuel Chanrion

Publications and source records attributed to Emmanuel Chanrion.

12 recordsLinked to original sources

arXiv2026

Automatic Charge State Tuning of 300 mm FDSOI Quantum Dots Using Neural Network Segmentation of Charge Stability Diagram

Tuning of gate-defined semiconductor quantum dots (QDs) is a major bottleneck for scaling spin qubit technologies. We present a deep learning (DL) driven, semantic-segmentation pipeline that performs charge auto-tuning by locating transition lines in full charge stability diagrams (CSDs) and returns gate voltage targets for the single charge regime. We assemble and manually annotate a large, heterogeneous dataset of 1015 experimental CSDs measured from silicon QD devices, spanning nine design geometries, multiple wafers, and fabrication runs. A U-Net style convolutional neural network (CNN) with a MobileNetV2 encoder is trained and validated through five-fold group cross validation. Our model achieves an overall offline tuning success of 80.0% in locating the single-charge regime, with peak performance exceeding 88% for some designs. We analyze dominant failure modes and propose targeted mitigations. Finally, wide-range diagram segmentation also naturally enables scalable physic-based feature extraction that can feed back to fabrication and design workflows and outline a roadmap for real-time integration in a cryogenic wafer prober. Overall, our results show that neural network (NN) based wide-diagram segmentation is a practical step toward automated, high-throughput charge tuning for silicon QD qubits.

cond-mat.mes-hall↗

arXiv2023

Electrical manipulation of a single electron spin in CMOS with micromagnet and spin-valley coupling

For semiconductor spin qubits, complementary-metal-oxide-semiconductor (CMOS) technology is the ideal candidate for reliable and scalable fabrication. Making the direct leap from academic fabrication to qubits fabricated fully by industrial CMOS standards is difficult without intermediate solutions. With a flexible back-end-of-line (BEOL) new functionalities such as micromagnets or superconducting circuits can be added in a post-CMOS process to study the physics of these devices or achieve proof of concepts. Once the process is established it can be incorporated in the foundry-compatible process flow. Here, we study a single electron spin qubit in a CMOS device with a micromagnet integrated in the flexible BEOL. We exploit the synthetic spin orbit coupling (SOC) to control the qubit via electric field and we investigate the spin-valley physics in the presence of SOC where we show an enhancement of the Rabi frequency at the spin-valley hotspot. Finally, we probe the high frequency noise in the system using dynamical decoupling pulse sequences and demonstrate that charge noise dominates the qubit decoherence in this range.

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arXiv2022

Probing charge noise in few electron CMOS quantum dots

Charge noise is one of the main sources of environmental decoherence for spin qubits in silicon, presenting a major obstacle in the path towards highly scalable and reproducible qubit fabrication. Here we demonstrate in-depth characterization of the charge noise environment experienced by a quantum dot in a CMOS-fabricated silicon nanowire. We probe the charge noise for different quantum dot configurations, finding that it is possible to tune the charge noise over two orders of magnitude, ranging from 1 ueV^2 to 100 ueV^2. In particular, we show that the top interface and the reservoirs are the main sources of charge noise and their effect can be mitigated by controlling the quantum dot extension. Additionally, we demonstrate a novel method for the measurement of the charge noise experienced by a quantum dot in the few electron regime. We measure a comparatively higher charge noise value of 40 ueV^2 at the first electron, and demonstrate that the charge noise is highly dependent on the electron occupancy of the quantum dot.

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arXiv2022

Complete readout of two-electron spin states in a double quantum dot

We propose and demonstrate complete spin state readout of a two-electron system in a double quantum dot probed by an electrometer. The protocol is based on repetitive single shot measurements using Pauli spin blockade and our ability to tune on fast timescales the detuning and the interdot tunnel coupling between the GHz and sub-Hz regime. A sequence of three distinct manipulations and measurements allows establishing if the spins are in S, Tzero, Tplus or Tminus state. This work points at a procedure to reduce the overhead for spin readout, an important challenge for scaling up spin qubit platforms.

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arXiv2022

Parity and singlet-triplet high fidelity readout in a silicon double quantum dot at 0.5 K

We demonstrate singlet-triplet readout and parity readout allowing to distinguish T0 and the polarized triplet states. We achieve high fidelity spin readout with an average fidelity above $99.9\%$ for a readout time of $20~μ$s and $99\%$ for $4~μ$s at a temperature of $0.5~K$. We initialize a singlet state in a single dot with a fidelity higher than $99\%$ and separate the two electrons while keeping the same spin state with $a \approx 95.6\%$ fidelity.

cond-mat.mes-hall↗

arXiv2022

Controlled quantum dot array segmentation via a highly tunable interdot tunnel coupling

Recent demonstrations using electron spins stored in quantum dots array as qubits are promising for developing a scalable quantum computing platform. An ongoing effort is therefore aiming at the precise control of the quantum dots parameters in larger and larger arrays which represents a complex challenge. Partitioning of the system with the help of the inter-dot tunnel barriers can lead to a simplification for tuning and offers a protection against unwanted charge displacement. In a triple quantum dot system, we demonstrate a nanosecond control of the inter-dot tunnel rate permitting to reach the two extreme regimes, large GHz tunnel coupling and sub-Hz isolation between adjacent dots. We use this novel development to isolate a sub part of the array while performing charge displacement and readout in the rest of the system. The degree of control over the tunnel coupling achieved in a unit cell should motivate future protocol development for tuning, manipulation and readout including this capability.

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arXiv2021

Spin-valley coupling anisotropy and noise in CMOS quantum dots

One of the main advantages of silicon spin qubits over other solid-state qubits is their inherent scalability and compatibility with the 300 mm CMOS fabrication technology that is already widely used in the semiconductor industry, whilst maintaining high readout and gate fidelities. We demonstrate detection of a single electron spin using energy-selective readout in a CMOS-fabricated nanowire device with an integrated charge detector. We measure a valley splitting of 0.3 meV and 0.16 meV in two similar devices. The anisotropy of the spin-valley mixing is measured and shown to follow the dependence expected from the symmetry of the local confinement, indicating low disorder in the region of the quantum dot. Finally the charge noise in the spin-valley coupling regime is investigated and found to induce fluctuations in the qubit energy in the range of $0.6GHz/\sqrt{Hz}$.

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arXiv2021

Enhanced spin coherence while displacing electron in a 2D array of quantum dots

The ability to shuttle coherently individual electron spins in arrays of quantum dots is a key procedure for the development of scalable quantum information platforms. It allows the use of sparsely populated electron spin arrays, envisioned to efficiently tackle the one- and two-qubit gate challenges. When the electrons are displaced in an array, they are submitted to site-dependent environment interactions such as hyperfine coupling with substrate nuclear spins. Here, we demonstrate that the electron multi-directional displacement in a $3\times 3$ array of tunnel coupled quantum dots enhances the spin coherence time via the motional narrowing phenomenon. More specifically, up to 10 configurations are explored by the electrons to study the impact of the displacement on spin dynamics. An increase of the coherence time by a factor up to 10 is observed in case of fast and repetitive displacement. The physical mechanism responsible for the loss of coherence induced by displacement is quantitatively captured by a simple model and its implications on spin coherence properties during the electron displacement are discussed in the context of large-scale quantum circuits.

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arXiv2020

Distant spin entanglement via fast and coherent electron shuttling

In the quest for large-scale quantum computing, networked quantum computers offer a natural path towards scalability. Now that nearest neighbor entanglement has been demonstrated for electron spin qubits in semiconductors, on-chip long distance entanglement brings versatility to connect quantum core units. Here we realize the controlled and coherent transfer of a pair of entangled electron spins, and demonstrate their remote entanglement when separated by a distance of 6 microns. Driven by coherent spin rotations induced by the electron displacement, high-contrast spin quantum interferences are observed and are a signature of the preservation of the entanglement all along the displacement procedure. This work opens the route towards fast on-chip deterministic interconnection of remote quantum bits in semiconductor quantum circuits.

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arXiv2020

Charge detection in an array of CMOS quantum dots

The recent development of arrays of quantum dots in semiconductor nanostructures highlights the progress of quantum devices toward large scale. However, how to realize such arrays on a scalable platform such as silicon is still an open question. One of the main challenge resides in the detection of charges within the array. It is a prerequisite functionality to initialize a desired charge state and readout spins through spin-to-charge conversion mechanisms. In this paper, we use two methods based on either a single-lead charge detector, or a reprogrammable single electron transistor. Thanks to these methods, we study the charge dynamics and sensitivity by performing single shot detection of the charge. Finally, we can probe the charge stability at any node of a linear array and assess the Coulomb disorder in the structure. We find an electrochemical potential fluctuation induced by charge noise comparable to that reported in other silicon quantum dots.

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arXiv2018

Gate-Based High Fidelity Spin Read-out in a CMOS Device

The engineering of electron spin qubits in a compact unit cell embedding all quantum functionalities is mandatory for large scale integration. In particular, the development of a high-fidelity and scalable spin readout method remains an open challenge. Here we demonstrate high-fidelity and robust spin readout based on gate reflectometry in a CMOS device comprising one qubit dot and one ancillary dot coupled to an electron reservoir to perform readout. This scalable method allows us to read out a spin with a fidelity above 99% for 1 ms integration time. To achieve such fidelity, we exploit a latched spin blockade mechanism that requires electron exchange between the ancillary dot and the reservoir. We show that the demonstrated high read-out fidelity is fully preserved up to 0.5 K. This results holds particular relevance for the future co-integration of spin qubits and classical control electronics.

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arXiv2018

Coherent control of individual electron spins in a two dimensional array of quantum dots

The ability to manipulate coherently individual quantum objects organized in arrays is a prerequisite to any scalable quantum information platform. For electron spin qubits, it requires the fine tuning of large arrays of tunnel-coupled quantum dots. The cumulated efforts in linear dot arrays have permitted the recent realization of quantum simulators and multi-electron spin coherent manipulation. However, the two-dimensional scaling of such implementations remains undemonstrated while being compulsory to resolve complex quantum matter problems or process quantum information. Here, we demonstrate the two-dimensional coherent control of individual electron spins in a 3x3 array of tunnel-coupled quantum dots. More specifically, we focus on several key quantum functionalities of such control: charge deterministic displacement, local spin readout, local coherent exchange manipulation between two electron spins trapped in adjacent dots, and coherent multi-directional spin shuttling over distances of several microns. This work lays the foundations for exploiting a two-dimensional array of electron spins for quantum simulation and information processing.

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