M. Pioro-Ladrière

Université de Sherbrooke, Шербрук, Quebec, Canada

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Publications (70)236.52 Total impact

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    ABSTRACT: Silicon chips hosting a single donor can be used to store and manipulate one bit of quantum information. However, a central challenge for realizing quantum logic operations is to couple donors to one another in a controllable way. To achieve this, several proposals rely on using nearby quantum dots (QDs) to mediate an interaction. In this work, we demonstrate the coherent coupling of electron spins between a single 31P donor and an enriched 28Si metal-oxide-semiconductor few-electron QD. We show that the electron-nuclear spin interaction on the donor can drive coherent rotations between singlet and triplet electron spin states of the QD-donor system. Moreover, we are able to tune electrically the exchange interaction between the QD and donor electrons. The combination of single-nucleus-driven rotations and voltage-tunable exchange provides every key element for future all-electrical control of spin qubits, while requiring only a single QD and no additional magnetic field gradients.
    Full-text · Article · Dec 2015
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    ABSTRACT: Micro-magnets are key components for quantum information processing with individual spins, enabling arbitrary rotations and addressability. In this work, characterization of sub-micrometer sized CoFe ferromagnets is performed with Hall bars electrostatically defined in a two-dimensional electron gas. Due to the ballistic nature of electron transport in the cross junction of the Hall bar, anomalies such as the quenched Hall effect appear near zero external magnetic field, thus hindering the sensitivity of the magnetometer to small magnetic fields. However, it is shown that the sensitivity of the diffusive limit can be almost completely restored at low temperatures using a large current density in the Hall bar of about 10 A/m. Overcoming the size limitation of conventional etched Hall bars with electrostatic gating enables the measurement of magnetization curves of 440 nm wide micro-magnets with a signal-to-noise ratio above 10^3. Furthermore, the inhomogeneity of the stray magnetic field created by the micro-magnets is directly measured using the gate-voltage-dependent width of the sensitive area of the Hall bar.
    Full-text · Article · Nov 2015 · Applied Physics Letters
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    ABSTRACT: Tailoring spin coupling to electric fields is central to spintronics and spin-based quantum information processing. We present an optimal micromagnet design that produces appropriate stray magnetic fields to mediate fast electrical spin manipulations in nanodevices. We quantify the practical requirements for spatial field inhomogeneity and tolerance for misalignment with spins, and propose a design scheme to improve the spin-rotation frequency (to exceed 50MHz in GaAs nanostructures). We then validate our design by experiments in separate devices. Our results will open a route to rapidly control solid-state electron spins with limited lifetimes and to study coherent spin dynamics in solids.
    Full-text · Article · Jul 2015 · Applied Physics Express
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    ABSTRACT: The coherence time of a single-electron spin can reach tens of milliseconds when placed in the right environment [1]. The electric-dipole interaction between such a single spin and an electric field can be engineered by the inhomogeneous magnetic field of a micromagnet [2]. This effective spin-orbit interaction can be used to manipulate the spin through electric-dipole spin resonance [2], but also to couple a single spin to the electric field of a microwave cavity in the circuit QED architecture [3]. We selected the material and improved the shape of the micromagnet in order to maximize magnetic field gradients and remanence. We perform Hall magnetometry of those improved micromagnets using Hall bars electrostatically defined in an AlGaAs/GaAs two-dimensional electron gas. The gate-voltage dependent width of the Hall bar enables us to map the averaged magnetic field of the micromagnet, which validates simulations of the inhomogeneous magnetic field profile created by the magnet. We can therefore deduce that our micromagnets can produce magnetic field differences over 200 nm of more than 200 mT.\\[4pt] [1] M. Veldhorst et al., Nat. Nano. 1 (2014).\\[0pt] [2] M. Pioro-Ladri\`{e}re et al., Nat. Phys. 4, 2 (2008).\\[0pt] [3] X. Hu, Y. Liu, and F. Nori, Phys. Rev. B 86, 1 (2012).
    Full-text · Conference Paper · Mar 2015
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    ABSTRACT: We demonstrate fast universal electrical spin manipulation with inhomogeneous magnetic fields. With fast Rabi frequency up to 127 MHz, we leave the conventional regime of strong nuclear-spin influence and observe a spin-flip fidelity > 96%, a distinct chevron Rabi pattern in the spectral-time domain, and spin resonance linewidth limited by the Rabi frequency, not by the dephasing rate. In addition, we establish fast z-rotations up to 54 MHz by directly controlling the spin phase. Our findings will significantly facilitate tomography and error correction with electron spins in quantum dots.
    Full-text · Article · Nov 2014 · Physical Review Letters
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    Patrick Harvey-Collard · Dominique Drouin · Michel Pioro-Ladriere
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    ABSTRACT: In this work, we demonstrate a silicon nanocrystal Field Effect Transistor (ncFET). Its operation is similar to that of a Tunnelling Field Effect Transistor (TFET) with two barriers in series. The tunnelling barriers are fabricated in very thin silicon dioxide and the channel in intrinsic polycrystalline silicon. The absence of doping eliminates the problem of achieving sharp doping profiles at the junctions, which has proven a challenge for large-scale integration and, in principle, allows scaling down the atomic level. The demonstrated ncFET features a 104 on/off current ratio at room temperature, a low 30 pA/μm leakage current at a 0.5 V bias, an on-state current on a par with typical all-Si TFETs and bipolar operation with high symmetry. Quantum dot transport spectroscopy is used to assess the band structure and energy levels of the silicon island.
    Preview · Article · May 2014 · Applied Physics Letters
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    ABSTRACT: Tunneling in a quantum coherent structure is not restricted to only nearest neighbors. Hopping between distant sites is possible via the virtual occupation of otherwise avoided intermediate states. Here we report the observation of long-range transitions in the transport through three quantum dots coupled in series. A single electron is delocalized between the left and right quantum dots, while the center one remains always empty. Superpositions are formed, and both charge and spin are exchanged between the outermost dots. The delocalized electron acts as a quantum bus transferring the spin state from one end to the other. Spin selection is enabled by spin correlations. The process is detected via the observation of narrow resonances which are insensitive to Pauli spin blockade.
    Full-text · Dataset · May 2014
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    Full-text · Dataset · May 2014
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    Full-text · Dataset · May 2014
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    Full-text · Dataset · Jan 2014
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    ABSTRACT: We report measurements of electrical transport through single CdSe/CdS core/shell colloidal quantum dots connected to source and drain contacts. We observe telegraphic switching noise showing few plateaus at room temperature. We model and interpret these results as charge trapping of individual trap states and therefore we resolve individual charge defects in these high-quality low-strain colloidal quantum dots. The few number of observed defects quantitatively validate the passivation method based on thick CdS shells nearly lattice-matched to CdSe cores first developped to suppress photoluminescence blinking. Finally, we introduce a figure of merit useful to efficiently distinguish telegraphic noise from noise with a Gaussian distribution.
    Full-text · Article · Jan 2014 · Nano Letters
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    ABSTRACT: Tunneling in a quantum coherent structure is not restricted to only nearest neighbours. Hopping between distant sites is possible via the virtual occupation of otherwise avoided intermediate states. Here we report the observation of long range transitions in the transport through three quantum dots coupled in series. A single electron is delocalized between the left and right quantum dots while the centre one remains always empty. Superpositions are formed and both charge and spin are exchanged between the outermost dots. Detection of the process is achieved via the observation of narrow resonances, insensitive to the transport Pauli spin blockade.
    Full-text · Article · Dec 2013 · Physical Review Letters
  • Chloé Bureau-Oxton · Julien Camirand Lemyre · Michel Pioro-Ladrière
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    ABSTRACT: A quantum computer is a computer composed of quantum bits (qubits) that takes advantage of quantum effects, such as superposition of states and entanglement, to solve certain problems exponentially faster than with the best known algorithms on a classical computer. Gate-defined lateral quantum dots on GaAs/AlGaAs are one of many avenues explored for the implementation of a qubit. When properly fabricated, such a device is able to trap a small number of electrons in a certain region of space. The spin states of these electrons can then be used to implement the logical 0 and 1 of the quantum bit. Given the nanometer scale of these quantum dots, cleanroom facilities offering specialized equipment- such as scanning electron microscopes and e-beam evaporators- are required for their fabrication. Great care must be taken throughout the fabrication process to maintain cleanliness of the sample surface and to avoid damaging the fragile gates of the structure. This paper presents the detailed fabrication protocol of gate-defined lateral quantum dots from the wafer to a working device. Characterization methods and representative results are also briefly discussed. Although this paper concentrates on double quantum dots, the fabrication process remains the same for single or triple dots or even arrays of quantum dots. Moreover, the protocol can be adapted to fabricate lateral quantum dots on other substrates, such as Si/SiGe.
    No preview · Article · Dec 2013 · Journal of Visualized Experiments
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    ABSTRACT: Spin qubits involving one or two spins have emerged as potential building blocks for quantum information processing applications, resulting in many double quantum dot (DQD) studies. Coherent control of a two-electron spin qubit close to the singlet/triplet (S/T+) anticrossing through Landau-Zener-St\"uckelberg (LZS) oscillations has been studied theoretically and demonstrated experimentally in DQDs. Recent advances with triple quantum dot (TQD) technology have suggested additional advantages, such as their potential for encoding quantum information, that may soon be possible. Towards these goals we demonstrate, for for first time, the coherent manipulation of three-particle spin states in a TQD where all three spins play a role.
    Full-text · Article · Aug 2013 · Nature Physics
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    Full-text · Dataset · Jul 2013
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    Patrick Harvey-Collard · Abdelatif Jaouad · Dominique Drouin · Michel Pioro-Ladrière
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    ABSTRACT: Inductively Coupled Plasma (ICP) etching of amorphous silicon (a-Si) nanostructures using a continuous C4F8/SF6 plasma over nanotopography in silicon dioxide (SiO2) is investigated. The coil power of the ICP system is used to tune the a-Si etch rate from 20 to 125 nm/min. The etch rates of a-Si, SiO2 and electroresist are measured depending on the SF6 ratio, platen power and chamber pressure and used to optimize the a-Si:SiO2 etch selectivity. The results on nanostructures show that the presence of an insulating etch-stop layer affects the passivation ratio required to achieve vertical sidewalls. A low pressure is also necessary in order to etch the silicon nanostructure embedded into the oxide nanotrenches to form a highly conformable a-Si nanowire. We argue that both of these behaviors could be explained by surface charging effects. Finally, etching of 20 nm a-Si nanowires that cross 15 nm trenches in oxide with vertical sidewalls and a 4.3:1 a-Si:SiO2 etch selectivity is demonstrated. This etching process can be used in applications where nanotopography is present such as single electron transistors or multigate transistors.
    Full-text · Article · May 2013 · Microelectronic Engineering
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    ABSTRACT: Spin qubits based on interacting spins in double quantum dots have been demonstrated successfully. Readout of the qubit state involves a conversion of spin to charge information, which is universally achieved by taking advantage of a spin blockade phenomenon resulting from Pauli's exclusion principle. The archetypal spin blockade transport signature in double quantum dots takes the form of a rectified current. At present, more complex spin qubit circuits including triple quantum dots are being developed. Here we show, both experimentally and theoretically, that in a linear triple quantum dot circuit the spin blockade becomes bipolar with current strongly suppressed in both bias directions and also that a new quantum coherent mechanism becomes relevant. In this mechanism, charge is transferred non-intuitively via coherent states from one end of the linear triple dot circuit to the other, without involving the centre site. Our results have implications for future complex nanospintronic circuits.
    Full-text · Article · Feb 2013 · Nature Nanotechnology
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    Toshiaki Obata · Michel Pioro-Ladrière · Yasuhiro Tokura · Seigo Tarucha
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    ABSTRACT: We report on the Overhauser shift (OHS) of electric dipole spin resonance peaks in the reverse direction to that previously reported. Measuring electric dipole spin resonance in a double quantum dot, we observe two resonance peaks reflecting a Zeeman energy difference between the two quantum dots, and find that the dependence of the peak position on microwave power is different for each dot. The perturbation theory for hybridizing the flip-flop and photon-assisted tunneling mechanisms is discussed and is found to successfully explain the power dependence. This theory can also consistently explain the OHS in both directions, explaining the experimental results previously reported. Our results reveal the bidirectionality of OHSs and this is expected to play an important part in the development of effective nuclear spin squeezing techniques.
    Full-text · Article · Dec 2012 · New Journal of Physics
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    ABSTRACT: Nitrogen-vacancy (NV) centers in diamond are a promising candidate as a solid state qubit memory for quantum information as they possess very long coherence times even at room temperature. Furthermore, NV centers are very sensitive to their electromagnetic environment and are addressable in the GHz frequency range. Here we review our progress towards the detection of single NV centers for the implementation of fast on demand coupling between NV centers and GHz electromagnetic fields. Precisely, we present efforts towards mapping NV centers with a cathodoluminescence setup. Developing such capability is important for patterning local one-qubit gates for the application of high amplitude electromagnetic fields as a tuning parameter.
    No preview · Article · Aug 2012 · International Journal of Nanoscience
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    ABSTRACT: The original spin qubit proposal [1] suggested a linear array of spins for quantum computations and the exchange interaction for 2 qubit operations. An essential component of the proposal was the ability to control pairwise the exchange interaction between neighbouring pairs of spins. In this work we experimentally demonstrate such a pairwise control of the exchange interaction between three spins localized in a triple quantum dot (TQD) device. The TQD potential was formed using electrostatic lateral split-gate technology on a GaAs/GaAlAs heterostructure with a high-mobility two-dimensional electron gas [2]. We employ fast pulsing technique based on the Landau-Zener-Stuckelberg (LZS) approach for creating and manipulating coherent superpositions of three spin quantum states [3]. We show that we are able to maintain coherence when increasing the exchange coupling of one spin with another while simultaneously decreasing its coupling with the third.[4pt] [1] D. Loss, and D.P. DiVincenzo, Phys. Rev. A57, 120-126 (1998).[0pt] [2] L. Gaudreau , et al., Appl. Phys. Lett. v.95, 193101 (2009). [0pt] [3] J.R. Petta, H. Lu, and A.C. Gossard, Science v.327, 669-672 (2010).
    No preview · Conference Paper · Feb 2012

Publication Stats

1k Citations
236.52 Total Impact Points

Institutions

  • 2003-2014
    • Université de Sherbrooke
      • Department of Physics
      Шербрук, Quebec, Canada
  • 2007-2011
    • Japan Science and Technology Agency (JST)
      Edo, Tōkyō, Japan
  • 2001-2006
    • National Research Council Canada
      • Institute for Microstructural Sciences (IMS)
      Ottawa, Ontario, Canada